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

[lookimback]

So, I've had this idea for a while. I want to make my headlights turn on when the wipers are on. It's the law here that headlights must be on when the wipers are on, and I think that's standard on new vehicles, but my 03 Mountaineer doesn't have that feature. I have auto headlights when it gets dark, and I think I can utilize the photo resistor from that system. I believe that if I place a transistor (Q1) in series with the photo resistor, then I will have a way to break the circuit and make the headlight micro controller think it's dark and then it will turn on the lights. The base of Q1 will be pulled to ground by Q2, Q3, or Q4, which are in series with the wiper switch. Schematics are attached. The 3 switches in my schematic represent the wiper switches and they would normally be in the off position, thus making the circuits for Q2, Q3, and Q4 open unless the wipers were on. Does it look like it will work?

[lookimback]

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

Although Q1 is correct with respect to the schematic, I believe I will ultimately need to put it in series between the headlamp micro and the photo resistor rather than the photo resistor and ground. In that case, the emitter would go to the photo resistor, the collector would go to the micro.

[lookimback]

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

Updated schematic

[lookimback]

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

I put it together on a breadboard using some BC547 NPN transistors, an LM7805, a photo resistor, and some 1.5k resistors because I didn't have any 1k. The circuit around Q1 turns on the green LED, which represents the headlight, but in the truck that will really be pulling down a pin on a microcontroller. So far, It works as I'd expected.

[lookimback]

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

It turns out that there is enough current flowing from base to collector of Q2, Q3, and Q4 to keep Q1 on, so I didn't need the separate connection to the v+. Instead, I moved the R1 to limit that current on Q1's base and eliminated the connection to v+. Revised schematic attached.

[lookimback]

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

I went back to the original version where Q1 gets it's power directly from v+. I added diodes D1, D2, and D3 to prevent current flow from base to collector. Also added diodes D4, D5, and D6 which will be in series between the wiper microcontroller and switches to prevent current flowing from my circuit into the micro and damaging it. I'm wondering if I also should have diodes between the switches and emitters to prevent current from the wiper circuitry from flowing into my circuit.

[sam_sam_sam]

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

Please let us know when you have a working prototype and would you please post the results

Thanks

I have a bad habit of not turning on my head lights on when it is just drizzling because I do not want to leave my head lights when not need or when I get out of the vehicle

No tickets yet but it just a matter of time before it will happen and if you can get it to work I will build one for myself

[lookimback]

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

Please let us know when you have a working prototype and would you please post the results

Thanks

I have a bad habit of not turning on my head lights on when it is just drizzling because I do not want to leave my head lights when not need or when I get out of the vehicle

No tickets yet but it just a matter of time before it will happen and if you can get it to work I will build one for myself

I'll definitely post my results if I get it to work.

[lookimback]

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

So, after some research, I'm pretty sure the sunload sensor is a photodiode, not a photoresistor. I've realized at this point I need to get under the dash and see what my voltages are on the wire from the sunload sensor, and also from the wiper switch in both their on and off states. It's been raining all week and I don't have a garage. It's clear today but I probably won't have any free time before dark.

[lookimback]

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

Finally got under the dash today. The wires coming from the wiper switch are at 12v when the wipers are off, and when the switch is at on of the contact positions for any particular wire, it gets pulled to ground. The wire on the sunload sensor which goes to the headlight microprocessor was at 2.2v when exposed to sunlight, and 4.2v when covered. Covering it also made the headlights come on. So, I just need to supply 4.2v to the headlight microcontroller when the wipers are on, and do so without damaging the existing systems.

[budm]

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

When you turn on the wiper switch, does it stay grounded even when the wiper is in the intermittent mode?
So the 2.2V when the sensor is exposed is measured at the sensor output or at the processor input? I expect it to be <1V at the processor for it to consider as the logic LO.

[lookimback]

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

It does stay grounded in intermittent mode. 2.2v was at sensor. The output from that sensor goes to the security control module, which is way in the back (about where the back of the rear seat is), so maybe 10 feet or more from the sensor. I'll be tapping in right at the sensor, since it's right in the center of the dash. Also, do I need to know the current draw on the sensor output, or can I just assume it's less than the 200ma the 2n3904 can handle?

[budm]

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

Try this:

[lookimback]

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

This is what I currently have. The Spice model works, but I haven't put it together on the breadboard yet. The 12V going to each of the switches is just to simulate the 12v on those lines when the wipers are off and is just for the purpose of getting the model to run. The wiper switch is technically 4 separate switches which all turn together, but I figured out that I could access all possible switch positions by tapping into only 3 of the wires. Those are the 3 indicated by color codes on the below attachments. The way I currently have it, when the wipers are turned on Q1 switches off (cutting the true output from the sensor), and Q2 switches on which provides 4.2v from the regulator. Did I make it more complicated than I had to? I'm thinking I could do away with Q1 and use the diode to protect the sensor, and then use a zener as you did to provide the 4.2v.

[lookimback]

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

I incorporated your sketch into my design. Below are my results. If I change the 8.2k resistor to 5k, my Spice model says I'll get 3.37v output.

[budm]

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

https://www.badcaps.net/forum/attach...0&d=1532826258
When that Transistor Q1 is turned off the E-C (without the D6) in place the Voltage should be 1/2 of 12V with 5K/5K Voltage divider so Vr1 = 6V, and Vr8 = 6V, so with 8.2K/5K divider, the Vr8 should be 4.54V. The Zener is there for clamping in case R8 goes open circuit. Q1 is just an ON/OFF switch.
The Base drive of Q1 in your circuit is not fully turning off Q1.
What is the R7 for? and dk_blu, lt_blu, lt_blu/org?
You only need to sense one of the switches, the one that goes to ground since all the switches are turned together, right?
In my circuit, when the switch is at GND, Q1 is fully turned off.
You can remove R2, 3, 4, Q2, 3, 4 and connect Cathode of OR gate D1 to S1, D2 to S2, D3 to S3 if you want to sense all 3 switches. It is just simple OR gate to turn off Q1.

[lookimback]

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

I added a 3k pull-down resistor to Q1 because it wasn't turning off completely. Wiper switch schematic is attached. In order for this to work in all switch positions, I have to sense 3 of the switches. The dk_blu, lt_blu, lt_blu/org are the wires coming into the wiper switch which I have to sense. They have 12v on them when not grounded through the switch. R7 is only to put the 12v on those wires for the Spice simulation to be accurate.

[budm]

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

See my updated suggestion about not having those Transistors/resistors

[lookimback]

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

So I would have an OR gate with 3 inputs and if any switch turns on, Q1 turns off?

[budm]

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

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.