4017 counter reset problem

[barry wilkins]

I have been trying to make a counter for my vehicle alarm .I need to reduce the pulses that operate the hazard warning lights.
Because of the ECU you cannot connect directly to the lamps ,so I fitted a relay across the hazard switch. This works ,but because the number of pulses are odd this causes the lamps stay on ,and you have to switch them off by pushing the switch once.
I had a couple of ideas ,one was to use a couple of 74121 monostable ICs to give me 2 pulses.
The circuit I came up with is a Decade counter that uses counts 0 and 3 summing these together gives me the 2 pulses I need if I feed back count 4 or 5 as a reset
Occasionaly the second pulse returns to a high causing the relay to stay on, ,it seems like the reset might the the problem .
On the TI data sheet it does show a circuit using a 4001 to reset the IC.
Any thought on how I could solve this ?

Barry Wilkins

[televizora]

Re: 4017 counter reset problem

Can you provide a schematic of your alarm? Or at least detailed explanation how everything is connected and what you commutate.
Because there might be a much simpler solution or different solution.

[barry wilkins]

Re: 4017 counter reset problem

Hi not able to get multisim to work at the moment .
Soon as the weather improves I will first check the pusles that come out of the alarm with one of my scopes, sure that it was 5 pulses certainley an odd number which is causing the hazard light to stay on .If you set the alarm twice it cures the flashing problem.
At the moment I am testing the counter indoors using a 555 monostable with a run down control, think that might be my problem the clock is not stopping at the correct time.
So I am thinking of a redesign of the 555 circuit ,idealy it would be best if the reset from the counter stopped the clock pulses from the oscillator circuit.

Barry

[stj]

Re: 4017 counter reset problem

most alarms flash the lights a different number of times for "arm", and "disarm".
you should just make a board with some fets or "high-side drivers" on it to drive the light circuits.

[petehall347]

Re: 4017 counter reset problem

is this a can bus system ?

[barry wilkins]

Re: 4017 counter reset problem

No the alarm is not can bus ,but I expect the hazard lamps are ,as the lights seem to be controlled by an ECU.
What I did think ,if I changed the output to AC coupled it would not matter if the counter output remained at high.
As I said when the weather improves I will test the circuit in the vehicle .
Some reason I seem to have alot of time on my hands at the moment.

Barry

[barry wilkins]

Re: 4017 counter reset problem

Here is a picture of my first design

[televizora]

Re: 4017 counter reset problem

Just command the hazard lights via relay, while supplying them 12V directly from the battery. Use the original electrical wiring as control signal for the relay, then commutate 12V from the battery. So when you turn them on, they work. Then use a second relay, so you can command them via the alarm. So when either the alarm sends a signal to the relay to close or turn them on, they will work.
You need 2 relays and 1 plus wire from the battery.

[barry wilkins]

Re: 4017 counter reset problem

wont work the switch is binary ,the lamps are controlled by the ecu

[redwire]

Re: 4017 counter reset problem

In your first circuit, I would make some changes, such as adding a driver transistor for the relay because a 4017 has weak output drive a few mA. It would be a circuit that either counts to one or two. It depends if the alarm has a signal with a level for when "on", so you could add a gate to make the counter go to one or two depending if the alarm is set on or off.

[barry wilkins]

Re: 4017 counter reset problem

Hi think you are right about the transistor ,just knocked up a circuit to try ,a capacitor about 10 uF and a IRFBC30 mosfet (got lts of these) .
The output from the counter is now AC coupled so if the last count stays high it should not matter
Been thinking I am using the wrong type of counter,perhaps one that has a clear input would have been better
Been very busy last couple of day sorting out the SOVOS Tv for a friend ,what a pig to work on.
What I do need to do is to get Multisim working on this pc which is new.

Barry

[barry wilkins]

Re: 4017 counter reset problem

Thinking about it I decided to use two transistors in a darlington configuration .seems to work OK .
Next step is to try it out.