03 Mountaineer Auto headlamps when wipers are on. Does this look correct?

**lookimback** · 07-28-2018, 10:21 PM

Re: 03 Mountaineer Auto headlamps when wipers are on. Does this look correct?

Originally posted by budm

Yes, it is just simple diode OR gate, when any one of the 3 switches is GND it will turn off Q1. Just try that in you simulator.

It definitely works! Way simpler than I thought. I still need R6 and R9 for it to work though, does that seem right?

Attached Files

**budm** · 07-28-2018, 10:25 PM

Re: 03 Mountaineer Auto headlamps when wipers are on. Does this look correct?

You do need R5, R6 for biasing the Q1 ON, R9 can be left in.
The simulator still show only 3.85V on the Collector, what happen if you remove R6? So it looks like Q1 is still not fully turned off. may have to inscease value of R5 or replace R5 with diode with Cathode connected to the Base.
5K/13.2K * 12V = 4.54V

**lookimback** · 07-28-2018, 10:51 PM

Re: 03 Mountaineer Auto headlamps when wipers are on. Does this look correct?

If I remove R6 then I short my 12v to ground when the wipers are on. If I remove R6 and the trace completely, then I have 3.82v whether the wipers are on or off. Replacing R5 with a diode allows me to eliminate R9.

**lookimback** · 07-28-2018, 10:56 PM

Re: 03 Mountaineer Auto headlamps when wipers are on. Does this look correct?

I update the schematic. Resistors have different numbers now.

Attached Files

**lookimback** · 07-28-2018, 11:07 PM

Re: 03 Mountaineer Auto headlamps when wipers are on. Does this look correct?

If I remove the zener, I get the 4.5v we're expecting.

**budm** · 07-28-2018, 11:36 PM

Re: 03 Mountaineer Auto headlamps when wipers are on. Does this look correct?

https://www.badcaps.net/forum/attach...6&d=1532840149
If R1 is removed then Vr5 should be over 4V, Zener is rated at 4.7V so it should hardly conduct
If you draw a simple Voltage divider with just R4 (8,2K) connected in series and R5 (5K, connected in parallel with 4.7V Zener), what will Vr5 your simulator will show? As I indicate Q1 is just a switch , it is either ON or OFF.

That last updated circuit should work, but I would put the diode in series with R2 to make sure that Q1 is off when switch is GND.

**lookimback** · 07-28-2018, 11:53 PM

Re: 03 Mountaineer Auto headlamps when wipers are on. Does this look correct?

I tried a different 4.7v zener and it works now.

Attached Files

**budm** · 07-29-2018, 12:01 AM

Re: 03 Mountaineer Auto headlamps when wipers are on. Does this look correct?

OK, try it out on the real thing then.
I only simulator as the guide, it is only as good as what the parts library data are put in.

**lookimback** · 07-29-2018, 12:05 AM

Re: 03 Mountaineer Auto headlamps when wipers are on. Does this look correct?

Originally posted by budm

OK, try it out on the real thing then.

I'll mock it up on my breadboard tomorrow. Pretty sure I don't have a 4.7v zener, but I might have a 5.2v. That should be OK just for testing right?

**lookimback** · 07-29-2018, 12:07 AM

Re: 03 Mountaineer Auto headlamps when wipers are on. Does this look correct?

I appreciate your help too.

**budm** · 07-29-2018, 12:09 AM

Re: 03 Mountaineer Auto headlamps when wipers are on. Does this look correct?

That zener is just for clamping in case R5 goes open circuit so the porcessor will not see 12V at the input, so 5.2V will be fine, we just do not know what Voltage at the processor input can take.

**lookimback** · 07-29-2018, 12:23 AM

Re: 03 Mountaineer Auto headlamps when wipers are on. Does this look correct?

When I make a permanent one, I'll use a 4.7v. Also, I think I'll regulate the 12v because when the alternator kicks in, it should be about 14.6v.

**budm** · 07-29-2018, 01:52 PM

Re: 03 Mountaineer Auto headlamps when wipers are on. Does this look correct?

Originally posted by lookimback

When I make a permanent one, I'll use a 4.7v. Also, I think I'll regulate the 12v because when the alternator kicks in, it should be about 14.6v.

With that 4.7V zener in place, the highest the output will be 4.7 when 12V goes to 14.6V, no need to have 12V regulator.

**lookimback** · 07-29-2018, 03:53 PM

Re: 03 Mountaineer Auto headlamps when wipers are on. Does this look correct?

I'm experiencing some difficulties getting it to work on the breadboard. I've tried 3 different DC adapters which were rated 12v, 1.5amps or better. All had outputs of around 15-16v. No problems as far as the voltage goes, but with all 3, I had about 1.3v when the transistor was on, and over 6v when off. The strange thing is that if I switched the meter to AC, I had about 2.5v, but only if connected to the circuit. Tried 2 different meters (Fluke and Radio Shack), both exactly the same. Zener is a 5.1v 1N4733A, and I tried 3 different ones. Transistor is a BC547B. Resistors all measure very close to spec. Now, where it really gets strange is that I get that stray 1.3v even if I only have 1 probe connected. Tried turning lights off, thinking EMI, but no change. What's really strange is that with two 9v batteries in series, it functions somewhat as expected but only outputs 3.6v (17.2v input). I took it all apart and started over, still same results. All the resistors are 1/4 watt.

**lookimback** · 07-29-2018, 04:41 PM

Re: 03 Mountaineer Auto headlamps when wipers are on. Does this look correct?

I think it's working. I'm giving it 12.4v from my variac (12.4v after rectification), and I'm seeing about 4.03v output when I can get good connections. That's about what it should be. I can't figure out what that 1.3v when on is though, and even if I short emitter to collector, it's still there.

**budm** · 07-29-2018, 08:43 PM

Re: 03 Mountaineer Auto headlamps when wipers are on. Does this look correct?

When transistor is on (or E shorted to C) then the Voltage you see on the Cathode output of Diode OR gate will be from the 2.2V Sensor - Vf of the diode.

**lookimback** · 07-29-2018, 09:10 PM

Re: 03 Mountaineer Auto headlamps when wipers are on. Does this look correct?

I didn't simulate the sensor voltage in the prototype. The zener I was using was too big. 1N4733A is a 1w zener. My circuit didn't have enough current for it. I found a smaller one, still 5.1v, which was previously removed from a digital meter when I did my variac mod (when I added the digital display). Not sure the wattage, but it's way smaller and now it's working. Supply is 13.63v under load, and I'm seeing about 4.04 to 4.15v output.

Attached Files

**lookimback** · 07-29-2018, 09:19 PM

Re: 03 Mountaineer Auto headlamps when wipers are on. Does this look correct?

I didn't have the exact resistor values for the 3k and 5k. I used two 10k in parallel and two 1.5k in series. All 1/4w except R1. A 1/4w may have been ok, but R1 will dissipate almost 200mW. I thought that may be a bit too close and it did get warm. A 1/3 would have been ideal, but all I had was a 1w so that's what I used.

**budm** · 07-29-2018, 10:20 PM

Re: 03 Mountaineer Auto headlamps when wipers are on. Does this look correct?

Right now it is just prove of concept to see if will work in your car with noisy environment or not so I would not worry about resistor getting a little warm.
R3 can be 4.7K

**lookimback** · 07-29-2018, 10:35 PM

Re: 03 Mountaineer Auto headlamps when wipers are on. Does this look correct?

OK. I'll try it tomorrow.

03 Mountaineer Auto headlamps when wipers are on. Does this look correct?

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