Member postings for Maurice Taylor

Hi Tim ,

I asked you to connect led to battery and start the engine to see if it stayed lit,this would have proved your led was ok.

I suggest connecting the bulb to where the led was connected to check that wiring was ok.

Did the led across the battery stay alight with engine running ?

Sorry if I wasn’t very clear

Maurice

Duplicate ,deleted

Edited By Maurice Taylor on 21/08/2020 21:01:51

Hi Robert ,thanks for your reply ,faults like this usually are bad connections ,that’s what I tried to say early in the thread. I’ve had cars for 50 years and most electric faults have been bad connections etc. I appreciate your a busy man ,and don’t have time.

Maurice

Edited By Maurice Taylor on 21/08/2020 21:02:40

Hi Tim,

The above was what I posted ,if you still have one of your Leds connect it across the battery and see if it works as you won’t need to bend it.

Maurice

Hi Tim ,did you do any of the tests I suggested about 3 days ago regarding connecting your leds across battery?

Robert has already answered question about Picoscope. Go to ‘picotech.com’ for info .Software is free and runs in demo mode .Prices at around £100.

Maurice

Hi ,Robert

If you’ve got all this equipment ,why haven’t you done any experiments to show us all what spikes do to an led?

Maurice

Hi,

Just done a test with green led from junk box in series with 270 ohm resistor ,to test the effect of negative spikes,

Equipment used 12volt power supply,picoscope and 12volt car ht coil. I was able to produce an 80volt negative pulse ,did this a few times.Led and picoscope both connected across the coil.

Disconnected led ,connected it to 12volt supply still works.

All comments welcome good or bad

Maurice

Hi,

I can’t understand what is wrong with the specification.It simply says they work on a 9 to 12Volt supply with maximum

of 14Volt.            Please explain.

These will probably be bought by railway modellers,dolls house makers etc instead of bulbs surely all the info is there.

Maurice

Edited By Maurice Taylor on 19/08/2020 21:39:51

Hi,

Robert,

Tried green Led from junk box ,it suvived the spikes. If the car is still positive earth ,those spikes on my scope would be inverted ie 130V -ve and 20V +ve ,was it said previously in the thread that leds didn't like -ve pulses.This could be causing the led to fail.

I've given up with it now ,think I've tried my best,would welcome any comments on the above.

Tim,

You could probably try the idea/circuit suggested below.

The led is CPC Part No SC08786, Relay has 12V coil.

I have tried the circuit and the led draws 2.7mA from AA cells , they should last well.

Circuit is completely isolated from car electrics.

Comments welcome good or bad.

Maurice

Hi Tim ,

Is your car pos or neg earth ?

Are all the other led lamps ,plug in items made for cars ?

Maurice

Hi Robert

I have since tried the same clear Led with a 270 ohm resistor in series,works OK.

The Led I'm using is CPC Part no SC08786.

I think the experiment has proved spikes are not the problem,as Led is wired across points ,cant be any more spikey.

Regarding the box of electronics,it is a homebuilt ECU ,using an Arduino mega ,it will run the ignition using a homemade crank trigger wheel,a BMW crank sensor and a VW wasted spark coil.I haven't fitted fuel injection yet.

I can change from ECU ignition back to distributer ,by changing plug lead an power connection.

The project is known as Speeduino, plenty of info on internet.

Maurice

Edited By Maurice Taylor on 18/08/2020 16:23:35

Hi,

I have just tested my clear Led with 820 ohm resistor in series on my 40 year old coil and distributer ignition Fiesta.

1 Connected Led to battery, Led lit.

2 Started and revved engine ,left running 5 minutes ,still lit.

3 Turned engine off ,still lit.

4 Connected Led between points side of coil and ground.

5 Started engine ,Led lit ,revved as before,left running, still lit.

6 Stopped engine ,Led not lit, restarted engine ,Led lit

7 Connected Picoscope to check for spikes

The above is battery voltage with engine running.

The above is across the coil connected to Led leads

Hope this helps regarding spikes etc, negative spikes 20v positive approx 130 v

This is why I think there is a wiring fault in the car

The spikes do not affect the Led

Maurice

Edited By Maurice Taylor on 17/08/2020 14:19:15

They are available from sellers on Ebay.

Hi Tim,

I thought it could be a faulty earth between door and body but obviously not.

I always go for the simple things first with car electrics as earth faults give as many faults on new cars as they did on old ones

This is the reason for suggesting simple tests instead of complicating everything.

Maurice

Hi ,Tim

Where is the earth wire from the led connected ,is it connected to the main car body or to the door ?

Maurice

Hi, this test has been done previously in this thread. Why haven't other posters done this simple test. I've just done it myself using a clear led in series with a 820 ohm resistor, lights at 2.7v 0.2mA at 12v 11.4mA at 20v 21mA at 32v 38mA still did not blow (power supply doesn't go any higher ). I don't think zeners etc will make any difference.

Maurice

Hi Tim,

I would do the following,

1 Make a test lead ,with a 12v led ,length of black wire ,black crocodile clip,length of red wire,red crocodile clip.

2 Measure battery voltage with engine running.

3 Turn engine off

4 Connect test lead , led should light.

5 Leave test lead connected,start engine ,hopefully led should stay lit.If it stays lit there must be a problem with wiring to pressure guage.

6 If it blows ,fit new led to test leads,then disable generator either by disconnecting it or removing fan belt.

7 Connect test lead and start engine,if led stays lit ,this indicates a problem with the charging system,if it blows it suggests a wiring problem.

8 Make another test lead 12volt 5 watt bulb ,put this in place of led at pressure guage to see if it works or not.

Hope this helps,I know it seems a bit long winded but it takes longer to read it than do it.

Regarding voltage spikes ,put a supresser capacitor on th e HT coil , like when fitting a car radio.

Maurice

I would try connecting the led across the battery at the battery terminals ,the led will light.Then start the car if the led stays lit ,there is more than likely a problem with the circuit where it it is usually connected.It will prove whether the led is suitable or not.

Have you measured voltage across the led when the engine is running ,it will be more than 12V .Probably the led does not like the higher voltage .Try putting a resistor in series with the led, 470 ohms will do ,see what happens,might need different value series resistor.

Use the atmega 328 chip on its own ,you only need a crystal and 2 capacitors and it works the same as a Uno.

It will work on a supply between 1.7 and 5.5volt 

Edited By Maurice Taylor on 06/08/2020 16:19:54