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Retrofitted td5 speedo alarm red led

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Wondering if it's possible to connect the td5 speedo alarm red led [in centre of speedo face]  to this little led flasher unit when engine/ignition is off.  the text info below might help 

the unit currently operates a connected red led.

is it just a straight forward connect the plain pink speedo led wire to the output side of the units led connection ? 

what do our electrical wizards think ??

 

 

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Definitely can be made to work, but it might need a little more than 'just connect..'.

1) The only diagram I have to hand has slightly different labelling of the C1060 connector. I think its only a naming thing, but I think the correct wiring would be to connect your unit to pin 6, and ground pin 3 of the speedo. Pin6 on your diagram in 12V constant, but my diagram suggests its only for the led, and that the td5 alarm grounds pin 3 to light the led.

2) As I recall the led in the speedo has a series resistor for 12V, so you probably need to short out R15 in your flasher unit.

I'm not 100% certain on either of these - if no-one else chimes in I'll check the details when I can, but it might be a few days.

 

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.... thinking about it, it might be simpler to just add a single transistor to the led output of the flasher, and use it to drive the td5 led as normal (which now Ive read it properly, is what the photo text is suggesting).

(oops, that was meant to be an edit to the above - obviously too tired to be in charge of a keyboard!)

Edited by TSD
operator error
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Thanks for the reply,  :i-m_so_happy:

what type of transistor should I get ? as I'm not to familiar with these type of circuits 

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Send me a PM with your address and I'll put a couple in the post, with some instructions?

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I did this on my last 90, dieseljim made me a little flasher circuit which flashed the led when the ignition was off.

This time I was going to use it for for winch live power on but I had forgotten with all the other jobs.

Thanks for the reminder Ralph 👍

Mo

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I can't remember where this module came from, it might well of been dieseljim, but anyway

This is the module https://www.velleman.eu/support/downloads/?code=MK126 & the build info sheet attached below

just had a bit of a fiddle with it & the wires to speedo led. 

I can make the speedo led do this with the module connected as it should be 

the pink from speedo touched on the modules led red wire connection the speedo led lights up & flashes but not in time with the module led. 

 the components on the circuit board are covering most of the identies. so I'm not sure which is which, but the instruction sheets says R15 is yellow/purple/brown resistor, think its the one ringed in orange lower left, matches the colour coding

wiring on left is for the module led, wiring on right is 12v in & earth

looking at the back face of circuit board, I believe R15 goes along the top edge & along to the  joint marked as 1 which is the module led red wire

 

 

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manual_mk126.pdf

 

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thinking out loud, along with the transistor & info kindly supplied by TSD, can I keep the existing led as well, or not ? 

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I think you're right, though I was thrown by the awful pcb :rolleyes:, just from following the tracking in the photo. If you've got a continuity checker, connect one lead to the led positive lead, then check both ends of each possible candidate,  or just follow the tracking on the back of the board from the terminal block. The only component it connects to in the schematic is R15.

I will sketch on that photo a bit later on, to show how I would add the transistor.

And yes, you could probably keep the existing LED. but the mod I sent over will need to be a little bit different.

 

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Just catching up with this before heading to bed, 

thanks TSD for casting your eyes/brain over the above pics,  There's no big rush, to get this done asap, 

I've got a testlight probe/croc clip like this, would that be ok to use, ? 

I won't do any circuit board changes yet.

 

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Best not to use that on electronics, will be too many volts and/or too much current for some sensitive bits.

I just pulled a td5 speedo to bits to have a look, and I cant seen much evidence that the 12v feed to pin 6 of C1060 is used for anything other than the LED. So I would simply short out R15 on the velleman pcb and connec the led output to pin6 (positive) and pin 3 (negative) on the speedo. It probably works fine even with R15 left in, but it might be a bit dim in daylight. It almost certainly wont work with the second led in place, but it is easier than adding the transistor.

If you can solder, you could remove R15 (gently) from the board and replace it with a piece of wire. Then put R15 in the wire to the original led, in series with it. That way, both leds should work, both wired to the terminals as per the instructions.

Not sure I explained that very well....

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Ok on not using the tester I have.

I can solder, might need a new tip on my soldering iron though & I've got some proper old type solder.

I'll have a go at removing R15 & fitting a piece of wire in it's place & put R15 in the original led wiring, probably at the weekend & see what result we get, 

 

found & bought another kit here https://cpc.farnell.com/velleman-kit/mk126/electronics-kit-dummy-car-alarm/dp/HK01441 so I/we can play about with this kit & fit it as a plug & play once we've proved it works. 

Edited by western

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the new kit arrived today, what we believed to be R15 location is correct. 

so intention is to leave the existing module as is adjust this one to operate the Speedo red led. 

its says max current draw is 12ma, so both operating will be totaling 24ma shouldn't worry my battery to much.

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Calling TSD 

had to buy a new soldering iron, my existing one packed up after fitting 6 of the  resistors. 

so the 2nd module has been built up, I've not fitted R15 yet. I have a suitable piece of wire to fit in R15 location, as you mentioned above,

If I do that & leave R15 out of the circuit completely, then connect the right hand end connector block into a 12v/earth & the speedo led to the left hand hand connector block it should work ??? 

 

Quote

I will sketch on that photo a bit later on, to show how I would add the transistor.

will I still have to fit the transistor you sent ? 

 

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With R15 replaced by a piece of wire, and connected to the speedo as I mentioned above, then no transistor needed, it should work as expected. It's possible the circuit cannot drive two leds safely though, what's the number on the top of the IC?

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Thanks very much for that bit of info, I'll fit the bit of wire & test it tomorrow 

would a bit of wire the same size as the resistor/capacitor legs be sufficient for the jumper at R15 or something a bit thicker ? 

IC has 67MYFEE3 - LM324N printed on its case hopefully readable on this photo too.

 

quite enjoyed soldering this together, most electronics I've done for years 

 

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Any old bit of wire will do. One of the cut-off legs from one of the resistors you just fitted is the traditional part to use :rolleyes:

LM324 is a sturdy old beasty, will drive 2 leds without complaint :)

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OK that's good to know, I've already shape a resistor leg cut off bit of wire, so I'll solder that in place later,  that's good to know about the IC, once the speedo led is working, I may slave in the existing led, so I've got 2 options now, will add the results later. 

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Well, it sort of works, cannot get the speedo led to go out with engine running doesn't seem to respond to the sensitivity adjuster on the module, 

the instruction say to adjust this with engine running until led is out,  [works fine on the other led module] 

made a short video so you can see whats happening 

wondering if the sensitivity adjuster needs to have more range of adjustment, are there different sizes with bigger range ? this one has  2K2 5801M printed on it [as in photo] 

 

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I'm a bit stalled with this little project now as I don't know what bits I need to make it work properly, 

so any input is gratefully recieved

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As designed the adjustment range should be roughly 11 to 15V (10.42 to 14.37V plus a diode drop for the pedants) , working from the schematic.

Have you checked the fitted component carefully, esp R1, R2. (It can be easy to confuse 470R with 4k7)

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the instructions say R1,2,3,4 are all the same 4K7.

The only 470 is R15 which is still in the bag of bits.

So pretty sure all components are in the correct locations.

 

 

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A photo's of the underside, variable resistor is bottom left of board.

 I've done somemore in natural daylight.

 

 

 

 

 

 

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Edited by western
photo's changed, 15/09/18.

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