[msinfo_us]

Originally Posted by voerman

Hi,

I'll take a stab at this:

Looking at his circuit diagram, I think pin 4 of the 555 timer should be connected to the wiper (center pin) of the R4 trimpot. Which makes sense because pin 4 is the reset line and R4 is used to set the threshold.

Lou

That is right -- pin 4 is conneted to R4 POT. Pin 5 is not in use. To test set R3 to minimum (max brightness), R4 in mid position, R1 and R2 to max resistance than adjust R4 until LED starts to blink (regardless of the speed at this point, stop once LED begins to blink from 9V or 12V power. this will make later adjustment in a car easer), adjust timing using R1 and R2, adjust brightness to desired level. You are ready to install timer in a car. Hope this helps.
If you are still having troubles double check your connections: if there is a dot on a diagramm -- it is connected, if no dot -- no connection.

[houston06]

Yea i wish someone down in houton was able to help me out who can preform this, im clueless with this nad dont want to risk messing it up, id pay if anyones interested

[hammyoni]

someones gota wana make a buck! There would be many buyers of this! im simply not confortable with this task, but would easily pay for the piece so I can pup it in and connect a few wires...

[Pink]

If you do this, do you void your warranty in any way with BMW?

[msinfo_us]

Originally Posted by Pink

If you do this, do you void your warranty in any way with BMW?

Short answer is "No" since nothing is effected by this mod. You only tap in to 12V power line with minimum current requiremts and protected by fuse. So even if you short some wires during install worse you'll blow a fuse. Having said so as with any mod "you do it at your own risk".

[JeeZues]

Hi msinfo,
I tried the original circuit you described but I'm only getting ~3v going to the LED when ON and 0.1V when OFF... Any hints?
Here is what I'm using:
- 12v source
- 12v LED
- R1 4.7-10K
- R2 4.7-10K
- R3 10-20K
- C1 1000uF 16V
- 555 Timer (http://www.thesourcecc.com/estore/Pr...roduct=2761723)
- D1 50V 1A 1N4001 (http://www.thesourcecc.com/estore/pr...roduct=2761101)

I think everything is connected right since I was able to use R3 to set the threshold (I tested with 12V and was getting ON/OFF and with 5V it was just OFF) and use R1 and R2 to adjust the frequency.

Thanks,
JZ

P.s. I'm no electronic expert, but I'm willing to learn

[msinfo_us]

Before I answer your question please keep in mind that the timer I am using is 555CP. You are using 555CN. There is possible variation (should not be a major one but your measurements might be slightly different) in a threshold value, current and voltage requirements. I did few quick tests using 9v battery (actual reading 9.48V) and it produced 8.4V to LED and 8.5V to pin 8 (after D1 and R3). Try the following troubleshooting steps:
1. Make sure if C1 is polarized (has assigned + and ground) you did not put it in a wrong way.
2. Put R3 in a minimum resistance position (all the way to the right or left depending on your implementation) to supply max V to the circuit for testing purpose.
3. Make sure R1 and R2 are NOT in minimum resistance position. Try MAX resistance for testing purpose.
4. Disconnect LED and use multimeter to take a V reading (depends on type of LED and your power source there might be a drop in source V/A when LED is ON that will explain drop in V out)
5. Take V measurements on R3 out pin/before D1 and after D1. V drop on a timer (V to the LED) should be within 0.1-0.5V max.
Let me know your V readings in each step it should help us to pin point the problem.

PS By original circuit I assume you meant circuit from page one of this thread.

[JeeZues]

Thanks msinfo,
You are right, I'm using the diagram from page 1... I'll try the latest setup when I get the parts for it.

I'm now using a 9V source giving 8.99V (must bet getting old)
The Cap was connected correctly, by chance
After step 4, I'm getting 7.35V (a good jump, but not sure if it is enough to light the LED)
5. I'm getting 7.35V on one side of the D and 8V on the other

Using a 12V (an old computer PSU) I'm getting 10.10V to the LED when ON and 0.11V when OFF

Ok... done more testing and the light is now blinking (I had the LED connected in reverse )

I'll work on the timing and go put it in the car after...

Thanks

[msinfo_us]

You are welome. Good job and congrats!

PS Try version two if you feel you need more brightness from LED/want more precise control. Personally I think version one is bright enough. But that is just me.

[jdInMaryland]

Hi msinfo_us - I noticed that the specs on the timer chip say that the minimum temperature is 32F. I am guessing that it works find in freezing temperatures, at least at the frequency and duty cycle that we need for this application? THANKS MUCH!

[msinfo_us]

Originally Posted by jdInMaryland

Hi msinfo_us - I noticed that the specs on the timer chip say that the minimum temperature is 32F. I am guessing that it works find in freezing temperatures, at least at the frequency and duty cycle that we need for this application? THANKS MUCH!

You are absolutely correct. In this implementation any variation in parameters are practically negligible -- for a example you'd have to be a superhuman to notice 1/100 of a second variation with 1 second and above duty cycle.

[schneid4323]

Ok when i saw Clown nose blinking LED I thought cool... I open it.... and now im reviewing circuitry... Well this should help me on finals THANKS!!!!

[cgnahc]

I'm trying this...Can't find all the damn parts at Radioshack. The C1 I have is much bigger also. I don't have the R3 or TLC555 timer. Anyone have spares to send me? (C1, R3, timer)

[msinfo_us]

Originally Posted by cgnahc

I'm trying this...Can't find all the damn parts at Radioshack. The C1 I have is much bigger also. I don't have the R3 or TLC555 timer. Anyone have spares to send me? (C1, R3, timer)

Did you try your local store or online?

It show "in stock" here http://www.radioshack.com/product/in...tId=2062595&cp

[JJP]

I attempted this project today, but ran into a few snags.

A couple of questions/observations for msinfo_us:

1) c1 (1000uf 50v) - the item is too big. Did you use a different one?

2) How do you know what resistor is 10k? The package comes with 100 resistors of different types. None of them are labeled.

3) Where can you find 20-30K for R3? It is not in the bundle mentioned.

Thanks for all your help on this DIY!!

Great Work!!

[rrandyy]

Using the following:
- R1 4.7-10K
- R2 4.7-10K
- R3 10-20K
- C1 1000uF 16V

You will get:
Time On = .693*(R1+R2)*C1 = 6 to 14 seconds
Time Off = .693*R2*C1 = 3 to 6 seconds
Frequency = 1/(0.693*(R1+2*R2)*C1)

This doesnt seem like it will be even close to the OEM spec. Using the other circuit mentioned, you get:

R1 = 100 Ohms
R2 = 3*10^6 Ohms = 3M Ohms
C1 = .22 mF = 220 * 10^-6 F = 220 uF

Then:
Time On = .693*(R1+R2)*C1 = 457 seconds
Time Off = .693*R2*C1 = 457 seconds
Frequency = 1/(0.693*(R1+2*R2)*C1) = .0011 Hz

Which also is totally off. So for those of you who built these circuits and got it to work properly, I'm very surprised. In fact, I'd like to hear back from someone who actually used the specs provided in this post and was successful.

To answer the question regarding figuring out the ohms of resistors, use the following color chart: http://www.csgnetwork.com/resistcolcalc.html

[msinfo_us]

Originally Posted by rrandyy

Using the following:
- R1 4.7-10K
- R2 4.7-10K
- R3 10-20K
- C1 1000uF 16V

You will get:
Time On = .693*(R1+R2)*C1 = 6 to 14 seconds
Time Off = .693*R2*C1 = 3 to 6 seconds
Frequency = 1/(0.693*(R1+2*R2)*C1)

This doesnt seem like it will be even close to the OEM spec. Using the other circuit mentioned, you get:

R1 = 100 Ohms
R2 = 3*10^6 Ohms = 3M Ohms
C1 = .22 mF = 220 * 10^-6 F = 220 uF

Then:
Time On = .693*(R1+R2)*C1 = 457 seconds
Time Off = .693*R2*C1 = 457 seconds
Frequency = 1/(0.693*(R1+2*R2)*C1) = .0011 Hz

Which also is totally off. So for those of you who built these circuits and got it to work properly, I'm very surprised. In fact, I'd like to hear back from someone who actually used the specs provided in this post and was successful.

To answer the question regarding figuring out the ohms of resistors, use the following color chart: http://www.csgnetwork.com/resistcolcalc.html

I am not going to start a debate and just going to assume you found correct datasheet for timer and did it right. This is one way of doing it ... please let me know how everything works and what value resistors/capacitor you end up using. I am sure there are a dozen ways and million value combinations that will work. What important is the ratio. It is such a simple board that I did not even bother doing the research and going thru calculations. I wanted to use parts I already had at hand so knowing that R1, R2 and C1 determine duty cycle I used whatever POT I had at hand for R1 and R2 and played with few different C1 options. When I got a combination that worked as I wanted to I called it a day and shared results here. I know of at least a dozen people who PMed/emailed me over time who finished this board. There is also a video on a second page that show duty cycle much shorter than what your calculations show ... But in any case I think your research will help people who want to replicate this board and can't find or want to use different parts to look at many differrent options -- so, thank you.

PS I just realized that I keep mistyping uF and mF again even in my second diagram. C1 supposed to be 0.1 - 0.5uF

[msinfo_us]

Originally Posted by JJP

1) c1 (1000uf 50v) - the item is too big. Did you use a different one?

Without removing board from the car I can't verify 100% but "yes" I think that is what I end up using (I think it was 1000/16V). In any case you don't have to use exactly same C1, anything between 10uF and 1000uF/no less than 16V should work. You'll just adjust duty cycle to desired time using R1 and R2.

Originally Posted by JJP

2) How do you know what resistor is 10k? The package comes with 100 resistors of different types. None of them are labeled.

The color codes are on a back of the package you bought. You can also use multimeter if you have it or you can use link above.

Originally Posted by JJP

3) Where can you find 20-30K for R3? It is not in the bundle mentioned.

Thanks for all your help on this DIY!!

Great Work!!

If you don't have 20-30K POT you can use regular resistors sequentially with POT at hand like this for example: + power to ---20K resistor to ---10K POT to ----D1. I'd recommend to start with just a 10K POT and add another 10K resistor if it is not enough than increase it until you get to the desired threshold. Let me know what do you have at hand and I’ll try to help you to choose a combo that will work.

[ejazbmw]

this is just way to confusing...

[msinfo_us]

Originally Posted by ejazbmw

this is just way to confusing...

I am sorry if this is confusing. All that is discussed in last few posts is duty cycle and corresponding values of R1, R2 and C1. The relation between R1, R2, C1 changes how long LED stays On and Off. The only point here is that you can use the same values I did or you can choose your own -- it does not really matter. I'd only stay away from very low values for R1 and R2. Otherwise you can experiment (or not if you choose to) as much as you want to using formulas above (Please note I did not check if formulas are accurate I just assumed that OP did his research) or just experiment with parts at hand.

[JJP]

A couple of questions/observations for msinfo_us:

1) Is it possible to create another wire diagram over a picture that is finished? Over the picture you did that allows you to adjust for brightness, like the one you did on page 1.

2) Can you tell me which direction the positive and negative point to for the led, pot, diode, etc?

Thanks, again!

[msinfo_us]

Originally Posted by JJP

A couple of questions/observations for msinfo_us:

1) Is it possible to create another wire diagram over a picture that is finished? Over the picture you did that allows you to adjust for brightness, like the one you did on page 1.

2) Can you tell me which direction the positive and negative point to for the led, pot, diode, etc?

Thanks, again!

+C1 to R2 and #6 and #2 on a timer. +LED to #3 on a timer, POT does not matter, R1,2,3,4 does not matter where + is, D1 to R3

JJP I thought you are building timer version one based on your picture above -- did you finish it and now want to try another version?