Can you make my 12v LED light up?

[Alec_t]

Good info again.
We were wrong about only one track break being necessary .
I've just noticed there is a possible short between the trimmer and Q1 collector. Make sure there is a track break between trimmer and collector. A short there explains the odd symptoms you've got.

 

[Dave 2000]

OK, broke the track as per your post, 12v supply no LED not even a glimmer. PWM to neg and still no LED, PWM to 12v and LED lights, trimmer allows me to turn LED off when PWM connected to 12v.

Altering voltage from 12v thru to 14 does not alter the above results. Should PWM to 12v or neg bring LED on or are we there Alec?

Regards

Dave

 

[Alec_t]

OK, broke the track as per your post, 12v supply no LED not even a glimmer. PWM to neg and still no LED, PWM to 12v and LED lights, trimmer allows me to turn LED off when PWM connected to 12v.

Ta-da! You've got there! Now connect up D4 and check that a simulated AC switch turns the green LED off.

 

[Dave 2000]

And yes, AC simulation amber on green off, you are the man Alec! I have a lot to do tomorrow but will try and get a test with the PWM controller.

I really appreciated the way you did not give up, TBH I was thinking I was getting components back to front, then there is the dodgy soldering and so on I might as well give up, that would have been unfair to you given the time put in.

Unsure how to repay you mate for your efforts, unlikely to be in Wales anytime soon or I could have bought you a beer, coming to southern Spain in the near future?

I will check back when final testing is complete.

Many thanks

Regards

Dave

 

[Alec_t]

I'll enjoy a simulated beer. Cheers, Dave!

 

[Dave 2000]

Hi Alec, er enjoy the beer , when it's finished we have a problem.......well two actually.

I connected the circuit up and the LED starting flashing fairly fast, this with the temperature sensor cold and fan off. I turn the trimmer down and the LED went out. I brought the coolant sensor up to temperature and the fan started slowly in the expected fashion, the LED did not respond.

The only way to get the LED to light was to turn the trimmer clockwise and now it is flashing very fast, at full fan speed the LED is virtually on solid it is flashing so fast.

So, LED flashes as soon as connected to PWM, trimmer turns it out.

LED will not light as PWM pulse increases in frequency.

PWM and fan work perfectly as expected regardless if LED circuit is connected or not.

Your thoughts mate?

Regards

Dave

 

[Alec_t]

Sounds like the PWM frequency is a lot lower than the 20kHz I assumed. Increasing C1 to 10uF or so (>=25V rated) should cure the flicker. You might be able to salvage a suitable cap from some dead/redundant kit.

LED will not light as PWM pulse increases in frequency.

I'm surprised the PWM frequency alters. Normally it's fixed and the duty cycle varies to change the fan speed.

Edit: Are you getting the +12V for the circuit from the switched IGN directly, or from the PWM'ed fan supply?

 

[Dave 2000]

I would not know the difference between duty cycle and frequency Alec. The fan has two heavy wires that go direct to the battery terminals, they stay permanently connected. The switched ign is supplying voltage to the PWM controller and our circuit, both come on at the same time, I note the green LED flickers just the once as the ignition is switched on.

Regards

Dave

 

[Dave 2000]

I note the capacitor is the same used in the earlier diagram, I have spares so will solder one in, I assume direct replacement position to the one fitted but is polarity sensitive?

I will get on that now,

Many thanks

Regards

Dave

 

[Alec_t]

I assume direct replacement position to the one fitted but is polarity sensitive?

Same position, but observe correct polarity. Usually a black stripe denotes the negative connection.

 

[Dave 2000]

Got it.

Regards

Dave

 

[Dave 2000]

OK, replacement capacitor in place, test will be done tomorrow am, let you know as soon as I have some info about result.

Many thanks

Regards

Dave

 

[Alec_t]

I don't know what your PWM voltage and duty-cycle signal characteristics are, but I've been simulating the circuit and I think it will respond better to the PWM signal if we move C1 so that it connects between the right-hand end of R1 and ground, i.e. it will then be connected in parallel with the trimmer. If the PWM signal can't then turn the green LED on at the 'sweet spot' where your fan cuts in, when the trimmer is fully adjusted, R1 can be reduced somewhat (by substitution or by putting another resistor in parallel with it). We don't want to go too low with R1 or it may load the controller excessively.

 

[Dave 2000]

Hi Alec, here is the update.

Connected everything up, LED on but not flickering, turned trimmer a little and the LED flickers, just another fraction of a turn and it is out.

Unfortunately it did not respond to the fan coming on even at full speed.

Having arrived home and catching your last post I will move C1today and retest.

Would there be any mileage in swapping back the R4 47k resistor or leave that at 10k?

Regards

Dave

 

[Dave 2000]

That's the one Alec!

Moving the capacitor completely changed the circuits behaviour, initial tests had the LED flickering multiple times during start up and stopping, a careful tweaking of the trimmer gave the faintest single flicker when starting and stopping, blink and you miss it as the LED goes to full brightness.

AC activation brought on the amber LED and extinguished the green as per the original plan so,

Alec you nailed it!

More thanks and a large crate of virtual beer!

One thing that disappoints me, on a forum involving vehicles I can call upon 48 years of 'under the bonnet' experience to help members get their trusty steeds working properly, here on this forum the best I can offer with my electronics knowledge is perhaps how to burn your car to the ground.

So sorry for the lack of future posts offering any help.

Many thanks Alec,

Regards

Dave

 

[Alec_t]

Well, we still don't know the true nature of the PWM signal, but hey, if it does the job that's great. Glad the circuit is now working as intended. Tweaking a few things here and there is par for the course with prototypes. R4 might as well stay at 10k.
Am on to the second bottle of that crate. Thanks, and cheers!

 

[Dave 2000]

@Alec_t "Am on to the second bottle of that crate."

I didn't drink at all before starting this project!

Take care, I am sure uour efforts will be rewarded some day.

Regards

Dave