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    Converting +/- 5v to a Usable Hz Signal

    Good morning.

    I have posted here before and have gotten AMAZING advise (thank you!). I'm back for more. This BCaps Sub Forum is so well attended I thought I would post here.

    This question is for an automotive application but has to do with what are essentially electrical questions and problem solving... If this is inappropriate I get it. Feel free to delete it or move the question.

    The V 12 Jaguar XJS is notorious for overheating in stop and go traffic in hot weather... Y'all will be potentially helpinh a LOT of people. The solutions and directions here will be shared on Jaguar Forums, a global jag forum.

    The 1990 Jaguar XJS uses a signal from a coolant temp sensor (a thermistor style sensor) to control spark and fueling. The sensor is supplied 5v by the ECU which reports a varying signal based on temperature . The sensors resistance decreases as temperature increases and visa versa. It then uses these values to determine spark duration, timing and fueling amounts.

    The idea is to take this varying V+ value (which newer jaguars do) and convert the varying voltage to a useable Hz value that can be used to run an OE electric PWModulation style cooling fan from a newer jaguar... On the newer cars, the fan units (LOTS and readily available) HAVE the PWM module built into the fan unit in various designs. It is really just a 2 wire connector with a signal (Hz?) coming from the ECU.

    One question is whether or not the ECU signal is ALREADY in a Hz form,,, OR whether the signal itself is in V and the module in the fan shroud makes the conversion. Many of the folks on the Jaguar Forum believe that the conversion from V to a useable Hz to PWM signal happens in the ECU. But that is not known.

    Is there a device similar to this one that can be used?

    The idea (SOMEHOW) is to use a thermistor sensor (or the OE signal from the one already on the car) and convert it's signal to drive the OE PWM cooling fan from a new vehicle.


    Heeeelp... What do y'all say?
    Attached Files

    #2
    Re: Converting +/- 5v to a Usable Hz Signal

    Review perhaps this:

    https://www.amazon.ca/Voltage-Conver.../dp/B07V3VHGXC

    Comment


      #3
      Re: Converting +/- 5v to a Usable Hz Signal

      Had a few days off at the Sea!

      Thanks for the reply!
      I should have provided this info in the first post! Actually a Jag Forum member pointed out, I had missed it. It's the operating range for the fan - it's not something I fully understand. 140hz?

      Pls see photo. It's the EM80-51 line...

      Much much appreciated!
      Attached Files

      Comment


        #4
        Re: Converting +/- 5v to a Usable Hz Signal

        Someone on the forum suggested something like this but there is a lot of information involved and toooooo much of it goes right over our heads (on the forums)...

        https://www.hicomponent.com/0-5v-0-1...er-module.html

        Comment


          #5
          Re: Converting +/- 5v to a Usable Hz Signal

          This is about the extent of the electrical info available...


          From the EG, the signal from the ECM to the FCM is:- "EM80-51 COOLING FAN MODULE CONTROL: PWM, 140Hz, POSITIVE DUTY CYCLE RANGE 7% – 95%"

          Output from the coolant temp. sensor to the ECM is:- "EM80-70 ENGINE COOLANT TEMPERATURE SENSOR SIGNAL, NOMINAL 0 – 5 V: NTC SENSOR – VOLTAGE DECREASES AS TEMPERATURE INCREASES"

          Comment


            #6
            Re: Converting +/- 5v to a Usable Hz Signal

            If I understand you, you want to add a variable speed feature to the older generation ECU on/off fan control?

            Most cars use simple on/off control with a relay for the cooling fan(s). In stopped traffic it bakes the engine compartment before the fan runs for a minute or two, not ideal.
            You're talking about variable speed (proportional) fan control using PWM. Even two-speed is probably a huge improvement.

            If you have a few ECT voltage measurements at different temperatures (perhaps listed in the service manual), it is possible to reverse-engineer the ECT sensor voltage into a temperature.
            Some ECU's have multi-range ECT circuits, where they switch in different resistors based on temperature, to get better resolution. This would make it too hard to know if it's say 3.5V what range is that.

            You want the fan off below a certain engine temperature, but I have seen Honda outright turn the engine cooling fan on whenever the cabin fan is turned on, or the A/C is turned on.

            If the thermostat is standard 80°C/176°F, having the fan start low speed at say 90°C/190°F and then ramp up to full speed at 100°C/212°F is kind of what you want?

            The cooling fan module pic looks like solid-state mosfets, so a 140Hz PWM signal fed (5V?) in will modulate the cooling fans' speed.
            I think you'd have to have adjustable fan-start temperature, as well as ramp up.

            Comment


              #7
              Re: Converting +/- 5v to a Usable Hz Signal

              Originally posted by redwire View Post
              If I understand you, you want to add a variable speed feature to the older generation ECU on/off fan control?

              Most cars use simple on/off control with a relay for the cooling fan(s). In stopped traffic it bakes the engine compartment before the fan runs for a minute or two, not ideal.
              You're talking about variable speed (proportional) fan control using PWM. Even two-speed is probably a huge improvement.

              If you have a few ECT voltage measurements at different temperatures (perhaps listed in the service manual), it is possible to reverse-engineer the ECT sensor voltage into a temperature.
              Some ECU's have multi-range ECT circuits, where they switch in different resistors based on temperature, to get better resolution. This would make it too hard to know if it's say 3.5V what range is that.

              You want the fan off below a certain engine temperature, but I have seen Honda outright turn the engine cooling fan on whenever the cabin fan is turned on, or the A/C is turned on.

              If the thermostat is standard 80°C/176°F, having the fan start low speed at say 90°C/190°F and then ramp up to full speed at 100°C/212°F is kind of what you want?

              The cooling fan module pic looks like solid-state mosfets, so a 140Hz PWM signal fed (5V?) in will modulate the cooling fans' speed.
              I think you'd have to have adjustable fan-start temperature, as well as ramp up.


              The hope/want is to use a set of OE PWM fans from a new more modern vehicle (there are millions of them and they are of very good quality) in an OLDER CAR that originally came as a mechanical fan set up OE...

              To gain an ability to drive/control the speed of the fans with a V signal (usually a varying 0-5v) from a coolant temperature sensor OE in the older car... The sensors business end is usually bathed in the cars coolant - reporting the temperature in a varying voltage form.

              In many automotive setups (older and newer cars) the coolant temp sensor is a thermistor type sensor,,, 5 volts comes into the sensor, as the temp of the coolant rises and falls the resistance of the sensor changes effecting/varying the voltage coming thru sensor. These voltages are understood by the ECU and translated to do many things.

              In this conversation/question the want is to take the signal from the coolant temperature sensor in an older car (that doesn't have PWM capabilities for cooling fan speeds built into the ECU) and somehow convert that voltage info into a usable and accurate PWM signal for the coolant fan control module from a newer car.
              Last edited by JayPoorJay; 08-09-2022, 05:15 PM.

              Comment


                #8
                Re: Converting +/- 5v to a Usable Hz Signal

                I'd say don't bother, feed it 100% duty cycle and bang/bang the control with hysteresis if desired. That's how it's done in cheap cars that mere mortals drive...

                Comment


                  #9
                  Re: Converting +/- 5v to a Usable Hz Signal

                  Originally posted by eccerr0r View Post
                  I'd say don't bother, feed it 100% duty cycle and bang/bang the control with hysteresis if desired. That's how it's done in cheap cars that mere mortals drive...
                  One car is a Porsche 928 (not used in this example) and the other is a 1990 Jag XJS v12... Both nice cars. The later definitely needs a solution as city driving in 90-100 degrees bumper to bumper is causing some real issues. Lots of folks, American classic muscle cars, to foreign cars with bigger engines etc could use some new tech ideas to smartly (and cheaply) have a solution to the ongoing problem...

                  And, it's a hobby - or mental illness - I'm not sure, lol
                  Attached Files

                  Comment


                    #10
                    Re: Converting +/- 5v to a Usable Hz Signal

                    You can't fix designs you don't have information to fix... and since the main reason for having the fan on is to cool it, just cool it like a CPU fan be damned with the noise or whatever issue those cars have that cheap cars don't...

                    Comment


                      #11
                      Re: Converting +/- 5v to a Usable Hz Signal

                      You can reverse-engineer what is needed with not so much work. It's kind of two parts - knowing the engine temperature, and controlling the fan(s).
                      I have a peer who does ECU design and will ask about working with the ECT voltage. There are actually only a few different types of thermistor used for ECT sensors, across all car makers. It's not that hard, but it is non-linear. You could take an op-amp and comparator to generate an analog fan speed signal, without interfering with the ECU.
                      That signal then goes into an IC to generate PWM even 555. This problem is a beaten horse just like the PC fan speed controllers that are out there. Many such circuits very similar to OP's need.

                      The fan controller needs to be some high current mosfets like in the Jag module. That likely uses 5V (or maybe 12V) PWM signal coming in to command the fan speed.

                      Comment


                        #12
                        Re: Converting +/- 5v to a Usable Hz Signal

                        Originally posted by redwire View Post
                        You can reverse-engineer what is needed with not so much work. It's kind of two parts - knowing the engine temperature, and controlling the fan(s).
                        I have a peer who does ECU design and will ask about working with the ECT voltage. There are actually only a few different types of thermistor used for ECT sensors, across all car makers. It's not that hard, but it is non-linear. You could take an op-amp and comparator to generate an analog fan speed signal, without interfering with the ECU.
                        That signal then goes into an IC to generate PWM even 555. This problem is a beaten horse just like the PC fan speed controllers that are out there. Many such circuits very similar to OP's need.

                        The fan controller needs to be some high current mosfets like in the Jag module. That likely uses 5V (or maybe 12V) PWM signal coming in to command the fan speed.
                        Right. On the older car, a 1990 Jaguar XJS, I don't want to go anywhere near the ECU. I want to see if I can hijack the coolant temp sensor signal (0v - 5v varying with engine temp - thermistor), even if I have to purchase a temp sensor and plug it into the coolant flow somehow, and use that signal to inform a device (like in the first response to the thread) that will convert that varying signal to an appropriate PWM signal to a OE coolant fan control module CFCM... CFCMs come with the used OE fans. I have to figure out the range that the CFCM would be looking for.

                        I'm not sure what co-amp and comparator means...
                        I'm not sure what "goes into an IC to generate PWM even 555", means.

                        I need all the help I can get, clearly 😊

                        Comment


                          #13
                          Re: Converting +/- 5v to a Usable Hz Signal

                          Sounds like you need someone to do it for you, I think we've given all the clues we can give without having access to the actual hardware... This won't be a "buy this connect that" solution.

                          Comment


                            #14
                            Re: Converting +/- 5v to a Usable Hz Signal

                            I see the wheel has already been invented. There are many aftermarket fan controllers for cars:
                            Summit Racing has several different makes and pricing.
                            Derale Performance
                            Hayden Automotive
                            Dakota Digital but primitive products on/off control only.

                            It's easiest if you can add a temperature sensor to the engine/rad, on a spare port etc. then you don't have to reverse-engineer the ECU.
                            Most of these fan controllers are basic for features and some not so great (read reviews Amazon).

                            The Jag fan module usually driven by an open-collector PWM output on the ECU, some are full speed when output on (0V) or off (12V), so you'd have to experiment to figure out what the module wants if you are using one.
                            Car ECT sensors there are two values that are used industry wide - thermistor with 10kΩ or 2.8kΩ at 25°C, and newer ECU's do the range-switching thing so the ECT voltage varies with range and not possible to deduce temperature from that.

                            https://forum.arduino.cc/t/use-activ...uino/648759/19

                            Comment


                              #15
                              Re: Converting +/- 5v to a Usable Hz Signal

                              Originally posted by redwire View Post
                              I see the wheel has already been invented. There are many aftermarket fan controllers for cars:
                              Summit Racing has several different makes and pricing.
                              Derale Performance
                              Hayden Automotive
                              Dakota Digital but primitive products on/off control only.

                              It's easiest if you can add a temperature sensor to the engine/rad, on a spare port etc. then you don't have to reverse-engineer the ECU.
                              Most of these fan controllers are basic for features and some not so great (read reviews Amazon).

                              The Jag fan module usually driven by an open-collector PWM output on the ECU, some are full speed when output on (0V) or off (12V), so you'd have to experiment to figure out what the module wants if you are using one.
                              Car ECT sensors there are two values that are used industry wide - thermistor with 10kΩ or 2.8kΩ at 25°C, and newer ECU's do the range-switching thing so the ECT voltage varies with range and not possible to deduce temperature from that.

                              https://forum.arduino.cc/t/use-activ...uino/648759/19
                              Yeah Red, there is NO shortage of products out there. Sad to say, and it's hard to believe, that none of them are any good. It's pretty mind blowing that some smart electronics dude hasn't seen a MARKET and come up with a quality, durable and usable product (HINT HINT HINT)...

                              I tried the "Northern Radiator" PWM fan controler. Installed it, placed the sensor, it got wet and shorted to full on. Lasted less than a week. WHY couldn't the designer understand that if one puts something on or near the radiator of a car there is a good possibility that it might/will see water. It's mind blowing. I'm chasing the manufacturer now,,, to see what they will do.

                              The crazy maker, is like you said, this isn't NEW technology. Cars have (millions of them) OE fan controllers that DO last the life of the car.

                              Very frustrating!!!

                              Comment


                                #16
                                Re: Converting +/- 5v to a Usable Hz Signal

                                Part way,,, maybe?
                                https://youtu.be/N-o8yFmQQgo

                                Comment


                                  #17
                                  Re: Converting +/- 5v to a Usable Hz Signal

                                  There may be a market... unfortunately very small.
                                  Can I make a $1000 plug and play device that does exactly what you need for the specific car/fan that you have, so that it compensates for the engineering time and limited market? My suspicion is that most people would balk at that option, hence none exist.

                                  But yes these better be waterproof or whoever making jury rig solutions should consider this fact, including the integrator...

                                  Comment


                                    #18
                                    Re: Converting +/- 5v to a Usable Hz Signal

                                    Take a look at this item

                                    http://thesensorconnection.com/cht-s...e-12-and-14-mm

                                    Then use a PWM controller that uses a temperature sensor for its input
                                    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


                                      #19
                                      Re: Converting +/- 5v to a Usable Hz Signal

                                      Good Morning, Sam. Thank you...

                                      In the motor world I have read about issues to do with trying to get accurate readings from a cylinder head or hard surface over changing conditions. Especially in a V12.

                                      Even still, the "gizmo" that this is connected to, that it's feed temp data to, that converts that data (temp) into a usable PWM signal is what I'm after. There is a prosuct from a gentleman, AutoCoolGuy, who has created a aftermarket (if it would be termed that way) solution that I hear work, and works well over time, but I would be walking away $300+ lighter. Doesn't sound like much BUT with 4 project car (2 of which would benefit from this solution) everything adds up. Death by 1000 cuts. More, others could benefit as well

                                      I would love to figure this out with available and cheap, well made OE components from the auto industry, a way to drive the fans without an ECU from the car as the middle man...

                                      The Northern Radiator gizmo (middleman) I got crapped out in one day. Shorted out after driving in the rain ONCE... Unreal.

                                      Comment


                                        #20
                                        Re: Converting +/- 5v to a Usable Hz Signal

                                        One solution would be if you know how to program a micro controller and use the type of sensor device I gave you a link to it would not be that difficult to do
                                        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

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