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    #21
    Re: How could I find a FET with specific specs?

    Originally posted by eccerr0r View Post
    Correct, need a common emitter or common source for mosfets. So that means low side, or use a p channel/pnp transistor. OP can use n channel/npn on the high side if they make a driver for them, which may complicate the circuit considerably.

    I'm facepalming because we're seeing the same problems that needs to be solved as the magnetic stirrer problem. Nothing learned... Insisting the final driver must be driven by an analog signal...
    That seems to be the case, isn't it?

    Does OP actually build the circut? If OP really wants to learn then build the circuit and report the results, the Voltage readings, the condition of the signals, etc. then you can analyze why the circuit is not doing what you want to do.
    Last edited by budm; 01-24-2021, 07:11 PM.
    Never stop learning
    Basic LCD TV and Monitor troubleshooting guides.
    http://www.badcaps.net/forum/showthr...956#post305956

    Voltage Regulator (LDO) testing:
    http://www.badcaps.net/forum/showthr...999#post300999

    Inverter testing using old CFL:
    http://www.badcaps.net/forum/showthr...er+testing+cfl

    Tear down pictures : Hit the ">" Show Albums and stories" on the left side
    http://s807.photobucket.com/user/budm/library/

    TV Factory reset codes listing:
    http://www.badcaps.net/forum/showthread.php?t=24809

    Comment


      #22
      Re: How could I find a FET with specific specs?

      Originally posted by EasyGoing1 View Post
      OK, so in terms of learning, I have no idea what "on the low side of the circuit" means at all ... also, "current monitor feedback" - no idea what that is either.
      Well, computer and keyboard are your friend so just do the research on those subjects.
      You have no idea how lucky you are have internet to access the knowledge world wide, in my days I would be lucky to find the info without waiting for months to get info on pieces of paper or spend lots of money at College book stores.
      Never stop learning
      Basic LCD TV and Monitor troubleshooting guides.
      http://www.badcaps.net/forum/showthr...956#post305956

      Voltage Regulator (LDO) testing:
      http://www.badcaps.net/forum/showthr...999#post300999

      Inverter testing using old CFL:
      http://www.badcaps.net/forum/showthr...er+testing+cfl

      Tear down pictures : Hit the ">" Show Albums and stories" on the left side
      http://s807.photobucket.com/user/budm/library/

      TV Factory reset codes listing:
      http://www.badcaps.net/forum/showthread.php?t=24809

      Comment


        #23
        Re: How could I find a FET with specific specs?

        Originally posted by budm View Post
        Well, computer and keyboard are your friend so just do the research on those subjects.
        You have no idea how lucky you are have internet to access the knowledge world wide, in my days I would be lucky to find the info without waiting for months to get info on pieces of paper or spend lots of money at College book stores.
        Hey I was there too ... I remember when Al Gore proposed his bill to fund the "Information Super Highway" - which was a federal budget created specifically to expand the Internet from the privileged few (governments and public education) out to the home via the Telco's. I was in my second year of college back then and didn't actually see Internet access until two years after that when I was a tech at Edwards AFB ... then AOL tapped in and started separating the men from the boys... lol

        And for the record, I did immediately look up current monitor feedback and was reading eagerly until I realized I started getting completely lost .... what I got from it though, was that a voltage feedback monitor basically takes a voltage and feeds it back to an opamp using a high impedance input on the opamp so that it would be the small voltage differences that guide the output of the opamp causing it to provide a more stable voltage, and current feedback would do something similar only it would be fed back into a low impedance on the op-amp so that it would be the current changes guiding the output of the opamp ... that's about as much as I was able to register before the propeller head tore off into all kinds of hieroglyphics ...

        Comment


          #24
          Re: How could I find a FET with specific specs?

          Originally posted by eccerr0r View Post
          I have to leave it up as an exercise to the reader to convert this to a 'low' side control.
          Low side control?




          Originally posted by eccerr0r View Post
          Thank you for putting the correct polarity/channel semiconductor in the schematic. Very important when dealing with the drive needed to turn on low/high side semiconductor switches.
          You're still upset over that little mistake? That was like ... 5 topics ago wasn't it?

          :-)

          Comment


            #25
            Re: How could I find a FET with specific specs?

            What do you guys think about something like this ... where picking different values for RO1, RO2 and RO3 as current limiting resistors for high, medium and low brightness in the LEDs, turning on only one of the three transistors at any given time?

            Comment


              #26
              Re: How could I find a FET with specific specs?

              Before you test that circuit and find it may not work as well as planned, do recall one LED turned on is dimmer than 2, and 2 on is dimmer than 3... so you may also be overthinking the problem.

              Comment


                #27
                Re: How could I find a FET with specific specs?

                This might seem like a stupid suction but why not use PWM function ( if this controller has this option) and
                only have one output

                You do have use the right setup for the transistor or mosfet that you would using

                I have done this a few time with a Basic Stamp and using the PWM function but you have to have output setup correctly I have even done this with an optic sensor ( like a 4N25 or something similar )

                For give me for saying this but you might be making this hard than it needs to be
                unless you have a special reason for doing it this way

                One note you do have to set parameters correctly with the PWM signal for this to also work correctly
                You might not be able to to go all the way down to 0% duty cycle and see the LEDs light very dimly but maybe down 10% depending on the controller and maybe as high as 75 to 80 for full on brightness in appearance to naked eye

                One other note you might even have to put a 1uf ( or less ) capacitor on the output pin of the controller and the negative side of the power supply to smooth out the pulses coming from the controller if they flicker to much ( see below )

                I once had to use this method for a solenoid valve coil hook up to Basic Stamp Controller using the PWM output to control a portioning hydraulic valve coil because the controller board for this machine took a crap for controlling this valve and to replace it would have cost to much money

                One final note this valve portioning power amplifier version has a feature that you can hook pot control to but because of the way valve works it would not always work correctly all the time and this was the reason for using a controller with a PWM controller function so it would work correctly most of the time

                The company that I worked for at the time really appreciate the fact I was able to fix this machine issue without having to spend a lot of money to do it ( this machine was about 20 years old )
                Last edited by sam_sam_sam; 01-25-2021, 03:28 PM.
                9 PC LCD Monitor
                6 LCD Flat Screen TV
                30 Desk Top Switching Power Supply
                10 Battery Charger Switching Power Supply for Power Tool
                6 18v Lithium Battery Power Boards for Tool Battery Packs
                1 XBox 360 Switching Power Supply and M Board
                25 Servo Drives 220/460 3 Phase
                6 De-soldering Station Switching Power Supply 1 Power Supply
                1 Dell Mother Board
                15 Computer Power Supply
                1 HP Printer Supply & Control Board * lighting finished it *


                These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10%

                1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later )
                2 Hem Saw Computer Stack Board

                All of these had CAPs POOF
                All of the mosfet that are taken out by bad caps

                Comment


                  #28
                  Re: How could I find a FET with specific specs?

                  The OP was using PWM except was not letting it through to the end device, insisting that the conversion happen early in the chain, thus wasting energy as well as increasing the dissipation requirements of the switching elements. The same problem was encountered in one of the previous projects the OP was working on yet persists on here.

                  In any case, proper drive needs to be figured out. OP apparently still hasn't figured out how to properly turn LEDs fully on and off - a requirement for PWM.

                  Comment


                    #29
                    Re: How could I find a FET with specific specs?

                    The one thing that you have to understand using the PWM signal from at least the micro controller ( the one that I am using ) is that full ON and full OFF is not the same thing as what you see with your naked eye with a led light bulb output you have to use a volt meter to measure the average voltage output signal

                    The way to solve the output issue with a micro controller device is turn on the output and get this to work first then use the PWM signal command and it should work correctly after

                    If you want to understand how a PWM output works on a micro controller look at page 356 of this manual and it explain it in some detail of how you would use it

                    Also in this manual it also has a section that shows you how to hook up a transistor to an output pin

                    I hope this helps
                    Attached Files
                    Last edited by sam_sam_sam; 01-26-2021, 05:27 AM.
                    9 PC LCD Monitor
                    6 LCD Flat Screen TV
                    30 Desk Top Switching Power Supply
                    10 Battery Charger Switching Power Supply for Power Tool
                    6 18v Lithium Battery Power Boards for Tool Battery Packs
                    1 XBox 360 Switching Power Supply and M Board
                    25 Servo Drives 220/460 3 Phase
                    6 De-soldering Station Switching Power Supply 1 Power Supply
                    1 Dell Mother Board
                    15 Computer Power Supply
                    1 HP Printer Supply & Control Board * lighting finished it *


                    These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10%

                    1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later )
                    2 Hem Saw Computer Stack Board

                    All of these had CAPs POOF
                    All of the mosfet that are taken out by bad caps

                    Comment


                      #30
                      Re: How could I find a FET with specific specs?

                      This is the article that has how to hook a transistor to a micro controller output pin

                      Plus it gives you the resistance values for what type of transistor you might be using

                      I have even use a 2N3904 it also works very well with a 1k ohm resistor if I remember correctly but this is at 5 volts output from the pin

                      I have also use ULN2803 before these are very easy to use as well and is also covered in this article below

                      These values might be different depending on how your micro controller input/output pins are configured

                      I am using the Basic Stamp Controller as an example because I have used this controller many times in the past and because it well documented and easy to find the information

                      As far as writing the code for the micro controller that you are using you would have to research for example codes to get a rough idea of how to correctly write the code

                      I have tried in the past to use a circuit simulator program and was not impressed with the results I have to actually build the circuit to see if it would work correctly or not

                      EasyGoing

                      One note I am NOT trying be little you

                      I am posting this information just in case you do not have a full understanding of how and what it takes to get this project to work

                      I hope this helps you and I hope you understand what my intentions are

                      Because I would like to see what you have in mind with this project that is the reason I am following it
                      Because I might learn something I did not know for maybe a future project

                      One interesting thing that has happened while looking up this information I found some information about a problem that I have been having using a battery spot welding machine controller board and this might help solve this issue

                      Here is the website that I found the answer to question about zero crossing and using the right optic sensor to a micro controller

                      https://microcontrollerslab.com/pc81...les-datasheet/

                      I found an error with the circuit diagram it does not show the right hook up for a load but it does give a code example which I am going to have to try
                      Attached Files
                      Last edited by sam_sam_sam; 01-26-2021, 07:39 AM.
                      9 PC LCD Monitor
                      6 LCD Flat Screen TV
                      30 Desk Top Switching Power Supply
                      10 Battery Charger Switching Power Supply for Power Tool
                      6 18v Lithium Battery Power Boards for Tool Battery Packs
                      1 XBox 360 Switching Power Supply and M Board
                      25 Servo Drives 220/460 3 Phase
                      6 De-soldering Station Switching Power Supply 1 Power Supply
                      1 Dell Mother Board
                      15 Computer Power Supply
                      1 HP Printer Supply & Control Board * lighting finished it *


                      These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10%

                      1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later )
                      2 Hem Saw Computer Stack Board

                      All of these had CAPs POOF
                      All of the mosfet that are taken out by bad caps

                      Comment


                        #31
                        Re: How could I find a FET with specific specs?

                        Originally posted by eccerr0r View Post
                        In any case, proper drive needs to be figured out. OP apparently still hasn't figured out how to properly turn LEDs fully on and off - a requirement for PWM.
                        Remember, the goal in this application is to have three different states of brightness, low, medium, and high.

                        The circuit where I had three different output pins driving three different transistors (TIP-120 in this case) actually worked.

                        However, based on the feedback here, I decided to try this configuration:



                        And after playing around with the RC filter, I settled on the values in the schematic. I used an online calculator which told me to use a 68Ω resistor and a 4.7uF cap but when I tried that, there was still significant ripple in the output so I bumped up the values and as you see here, the results are pretty good:


                        (This is at the medium brightness PWM duty cycle before attaching the MOSFET)

                        Yellow is channel 1 on the scope attached to the output pin of the Arduino chip and green is channel 2 attached to the output of the RC filter. It's still kinda noisy, but I think that has more to do with the Hanetk USB scope that I'm using, and my final power source will be a battery and not this buck converter that I'm using now which may also be part of the noise.

                        By varying the duty cycle of the PWM output, I am able to get three states of brightness ... basically, in the low state, I drive them at 90mA then at 170mA then on the highest setting, I get 270mA and the LEDs are rated at 280. And that is all from a 3.3V source.

                        Comment


                          #32
                          Re: How could I find a FET with specific specs?

                          This looks ok but I would have the one ohm resistor on each LED and remove the one the mosfet to negative side of the power supply

                          I might be wrong about this part it might not work correctly ——>
                          Or put the LEDs on the other side of the mosfet and have a resistor on each LEDs that goes to the negative side of the power supply

                          The reason why is so each led has the same current

                          Have you tried a raising value capacitor on the output pin to the negative rail of the controller and what results do you get ( or maybe put a 5 UF more before the resistor) with higher value ( just curious what the difference is with capacitors values I kind-a of know what might do but I only have experience doing it on the solenoid valve controller but have not tried this on LEDs before ) see if this makes a difference the only problem might be that response time for changing in brightness level will take longer ( this might be able to corrected this in the PWM code routine )

                          Can I ask you what are you making

                          Originally posted by EasyGoing1 View Post
                          By varying the duty cycle of the PWM output, I am able to get three states of brightness ... basically, in the low state, I drive them at 90mA then at 170mA then on the highest setting, I get 270mA and the LEDs are rated at 280. And that is all from a 3.3V source.
                          I am glad you are making progress on this project

                          Is the mosfet getting warm or hot driving it at full brightness or at low brightness what happens then
                          Last edited by sam_sam_sam; 01-26-2021, 12:08 PM.
                          9 PC LCD Monitor
                          6 LCD Flat Screen TV
                          30 Desk Top Switching Power Supply
                          10 Battery Charger Switching Power Supply for Power Tool
                          6 18v Lithium Battery Power Boards for Tool Battery Packs
                          1 XBox 360 Switching Power Supply and M Board
                          25 Servo Drives 220/460 3 Phase
                          6 De-soldering Station Switching Power Supply 1 Power Supply
                          1 Dell Mother Board
                          15 Computer Power Supply
                          1 HP Printer Supply & Control Board * lighting finished it *


                          These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10%

                          1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later )
                          2 Hem Saw Computer Stack Board

                          All of these had CAPs POOF
                          All of the mosfet that are taken out by bad caps

                          Comment


                            #33
                            Re: How could I find a FET with specific specs?

                            Originally posted by sam_sam_sam View Post
                            This is the article that has how to hook a transistor to a micro controller output pin

                            Plus it gives you the resistance values for what type of transistor you might be using

                            I have even use a 2N3904 it also works very well with a 1k ohm resistor if I remember correctly but this is at 5 volts output from the pin
                            A 3904 wouldn't work in this application because it has a rated maximum current that it can handle at 200mA and I need to push around 280. I think I'm close to the final circuit that I'll be using. I'm not sold on the IRF510N MOSFET YET ... I'd like to find something that can be driven with lower voltages - but only in the interest of that component consuming as little power as possible since this circuit will be running on a battery.

                            Originally posted by sam_sam_sam View Post
                            Because I would like to see what you have in mind with this project that is the reason I am following it
                            Because I might learn something I did not know for maybe a future project
                            Well, this project is what I affectionately call a "Hat Light" ... it's a flashlight that clips onto the bill of a baseball cap. I've already designed and printed the housing for it - in a mock setup at the moment, I haven't finalized the design yet, but here it is ... and YES, that's tinfoil epoxied into the cones ....



                            HOWEVER, I found some reflective PLA material that I want to use to print the cones with as you can see here:



                            After some testing with the reflective material, I'm not too happy with the way it works, and have been considering using this mirror finish spray paint that they have for plastic model projects which would no doubt work much better, BUT ... I had also planned on getting these thin sheets of clear acrylic that has a melting point tens of degrees C lower than PLA, which means if I print the cones onto the plexiglass, it could possibly bond with it in the print process creating a protective transparent cover for the cones - but if I do that, then I can't spray paint the mirror finish on the inside of the cones ... so I'm not yet decided ... but the LEDs I've been experimenting within this post are significantly brighter than the LEDs I have in the prototype hat light now, which means they COULD be bright enough so that the lack of performance I get from the PLA reflective material might be offset and I could use it anyways and then print to the plexiglass sheet.

                            The microcontroller I'm using is an ATTINY85, here's the code that seems to work pretty well:

                            Code:
                            #include <Arduino.h>
                            #include <avr/sleep.h>
                            #include <avr/interrupt.h>
                            #include <BlockNot.h>
                            
                            #define BUTTON 3
                            #define P0 0
                            
                            #define LO 0
                            #define MED 1
                            #define HI 2
                            
                            int mode = 0;
                            
                            #define BUTTON_PRESSED digitalRead(BUTTON) == LOW
                            #define TOO_HIGH mode > 2
                            
                            BlockNot offTimer(2500);
                            
                            void setPins() {
                              pinMode(BUTTON, INPUT);
                              pinMode(P0, OUTPUT);
                            }
                            
                            void sleep() {
                              GIMSK |= _BV(PCIE);           // Enable Pin Change Interrupts
                              PCMSK |= _BV(PCINT3);          // Use PB3 as interrupt pin
                              ADCSRA &= ~_BV(ADEN);          // ADC off
                              set_sleep_mode(SLEEP_MODE_PWR_DOWN);
                              sleep_enable();             // Sets the Sleep Enable bit in the MCUCR Register (SE BIT)
                              sei();                 // Enable interrupts
                              sleep_cpu();              // sleep
                              cli();                 // Disable interrupts
                              PCMSK &= ~_BV(PCINT3);         // Turn off PB3 as interrupt pin
                              sleep_disable();            // Clear SE bit
                              ADCSRA |= _BV(ADEN);          // ADC on
                              sei();                 // Enable interrupts <---THIS IS THE PROBLEM
                              setPins();
                            }
                            
                            void allOff(){
                              analogWrite(P0, 0);
                            }
                            
                            void ledLow() {
                              analogWrite(P0, 193);
                            }
                            
                            void ledMedium() {
                              analogWrite(P0, 208);
                            }
                            
                            void ledHIGH() {
                              analogWrite(P0, 253);
                            }
                            
                            void setup() {
                              setPins();
                              allOff();
                              ledLow();
                            }
                            
                            void loop() {
                              if (BUTTON_PRESSED) {
                                offTimer.RESET;
                                delay(100);
                                while(BUTTON_PRESSED) {
                                  if (offTimer.ON_TRIGGER) {
                                    allOff();
                                    delay(1000);
                                    sleep();
                                    mode = -1;
                                  }
                                }
                                mode ++;
                                if (TOO_HIGH) mode = LO;
                                switch(mode) {
                                  case LO:
                                    ledLow();
                                    break;
                                  
                                  case MED:
                                    ledMedium();
                                    break;
                                  
                                  case HI:
                                    ledHIGH();
                                    break;
                                  
                                  default:
                                    break;
                                }
                                delay(1000);
                              }
                            }
                            Though I'm having a problem with the code in that while I can put the tiny85 to sleep just fine, It's not waking up properly so I'm trying to figure that out. One other option is just to add a button to the reset pin and use that to power it on, then the mode toggle button to power it off by holding it for about three seconds.

                            Originally posted by sam_sam_sam View Post
                            One interesting thing that has happened while looking up this information I found some information about a problem that I have been having using a battery spot welding machine controller board and this might help solve this issue

                            Here is the website that I found the answer to question about zero crossing and using the right optic sensor to a micro controller

                            https://microcontrollerslab.com/pc81...les-datasheet/

                            I found an error with the circuit diagram it does not show the right hook up for a load but it does give a code example which I am going to have to try
                            That optical-transistor device looks interesting ... I've never worked with anything like that before, but I'm wondering how tightly coupled output would be to any input signal since it's translated by light ... like how sensitive is it to small input fluctuations... which I assume would be dependent on how sensitive the receptacle of the light is inside the device.

                            Comment


                              #34
                              Re: How could I find a FET with specific specs?

                              Yes the proper way is to have individual resistors for each LED unless your LEDs are perfectly matched. In a prototype environment this is possible; in a production, not so much.

                              I think the OP got lucky that the mosfet likely won't get warm or hot at all due to the low/limited currents involved here. 270mA times negligible voltage drop in an ideal situation is not many watts of power.

                              However one thing that we're being lied to about is that the IRF510. These are not "logic level" FETs and will barely turn on if at all at 3.3V gate drive, again maybe you can cherry pick a device that will turn on, but in a production environment you'll get a lot of failures. A BJT here will guarantee turn on in all cases but it will limit LED voltages to 3.1V or so due to saturation voltage drop.

                              Comment


                                #35
                                Re: How could I find a FET with specific specs?

                                Originally posted by sam_sam_sam View Post
                                This looks ok but I would have the one ohm resistor on each LED and remove the one the mosfet to negative side of the power supply I might be wrong about this part it might not work correctly ——>
                                Or put the LEDs on the other side of the mosfet and have a resistor on each LEDs that goes to the negative side of the power supply

                                The reason why is so each led has the same current
                                Based on the LED Array calculator, that is actually the preferred way to do it (one resistor in each branch of the LED portion of the circuit) I just didn't have any 1 Ohm resistors to test with so I made one out of coil wire and connected it to the emitter. When I create the PCB, I'll use surface mount resistors and do it the right way.

                                Originally posted by sam_sam_sam View Post
                                Have you tried a raising value capacitor on the output pin to the negative rail of the controller and what results do you get ( or maybe put a 5 UF more before the resistor) with higher value ( just curious what the difference is with capacitors values
                                Are you talking about the RC filter portion? In an effort to smooth out the signal even better?


                                Originally posted by sam_sam_sam View Post
                                Can I ask you what are you making

                                I am glad you are making progress on this project

                                Is the mosfet getting warm or hot driving it at full brightness or at low brightness what happens then
                                See my post before this one on the details of what I'm making. And thank you! I'm glad to be making progress as well :-)

                                and NO, the MOSFET doesn't get warm at all but it's a pretty beefy MOSFET rated I believe at 5 amps - which I couldn't imagine driving it that hard especially without a heat sync. It would be nice to scale it down for the final PCB, but then again ... I do have a lot of real estate in this project for a relatively simple circuit.

                                :-)

                                Comment


                                  #36
                                  Re: How could I find a FET with specific specs?

                                  Originally posted by eccerr0r View Post
                                  However one thing that we're being lied to about is that the IRF510. These are not "logic level" FETs and will barely turn on if at all at 3.3V gate drive, again maybe you can cherry pick a device that will turn on, but in a production environment you'll get a lot of failures. A BJT here will guarantee turn on in all cases but it will limit LED voltages to 3.1V or so due to saturation voltage drop.
                                  I take great offense to being called a liar. I don't lie, what would be the point? How could I possibly get the right help in here if I lie about what I'm doing?

                                  Here is a picture of the exact MOSFET that I used in the test. I also uploaded the pic file itself so you can check the date and time on it or whatever to confirm that I just took that picture.

                                  Attached Files

                                  Comment


                                    #37
                                    Re: How could I find a FET with specific specs?

                                    Yeah you got lucky, the threshold voltage of these FETs are not cut out for 3.3V usage and if you mass produce, you'll find a lot that don't work as planned.

                                    And again you MUST COMPLETELY LOSE THAT CAPACITOR if you want to save energy from battery use. That sole capacitor is causing you to waste a lot of the energy stored in the battery.

                                    Comment


                                      #38
                                      Re: How could I find a FET with specific specs?

                                      Originally posted by eccerr0r View Post
                                      However one thing that we're being lied to about is that the IRF510. These are not "logic level" FETs and will barely turn on if at all at 3.3V gate drive, again maybe you can cherry pick a device that will turn on, but in a production environment you'll get a lot of failures. A BJT here will guarantee turn on in all cases but it will limit LED voltages to 3.1V or so due to saturation voltage drop.
                                      And here is a video of it actually working...

                                      https://youtu.be/gLwZeiql5uc

                                      Comment


                                        #39
                                        Re: How could I find a FET with specific specs?

                                        Originally posted by eccerr0r View Post
                                        That sole capacitor is causing you to waste a lot of the energy stored in the battery.
                                        But the capacitor is part of the RC filter which smooths out the PWM and eliminates flickering which you wouldn't think would be detectable but I can "feel" it when the LEDs are lit, I can't look directly at them because they are too bright, but I can sense the flickering when I don't use the RC filter. I'll see if the flickering doesn't show up on video if I take that portion out of the circuit.

                                        Besides ... I don't see how the cap could cause any more loss than not having it since it's only mitigating the signal coming out of the microprocessor which can only put out a max of 40ma at the 3.3V that it's being fed.

                                        Comment


                                          #40
                                          Re: How could I find a FET with specific specs?

                                          Originally posted by eccerr0r View Post
                                          you MUST COMPLETELY LOSE THAT CAPACITOR if you want to save energy from battery use. That sole capacitor is causing you to waste a lot of the energy stored in the battery.
                                          You could do that but what you would have is the LEDs pulsing
                                          If you do not want to have this effect then you have to put this capacitor on the output pin

                                          Trust me I have run into this problem before

                                          Now you are probably right trying to run the mosfet at 3.3 volts might have issues I would agree with you about this

                                          And if this is the case then use a ULN2803 which I mentioned earlier and if I can remember correctly I think you use it all the way down to 3 volts but you would have to look at the data sheet to make sure
                                          Last edited by sam_sam_sam; 01-26-2021, 12:58 PM.
                                          9 PC LCD Monitor
                                          6 LCD Flat Screen TV
                                          30 Desk Top Switching Power Supply
                                          10 Battery Charger Switching Power Supply for Power Tool
                                          6 18v Lithium Battery Power Boards for Tool Battery Packs
                                          1 XBox 360 Switching Power Supply and M Board
                                          25 Servo Drives 220/460 3 Phase
                                          6 De-soldering Station Switching Power Supply 1 Power Supply
                                          1 Dell Mother Board
                                          15 Computer Power Supply
                                          1 HP Printer Supply & Control Board * lighting finished it *


                                          These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10%

                                          1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later )
                                          2 Hem Saw Computer Stack Board

                                          All of these had CAPs POOF
                                          All of the mosfet that are taken out by bad caps

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