Headlight Controller (PIC-based)

Saab9-5 · 04-21-2005, 04:06 PM

This is a circuit in response to JBraddoc's request from thread http://www.mp3car.com/vbulletin/wireless-communications/47177-bluetooth-rfid.html.

The PIC will control the lights through relays that are optoisolated from the controller. Inputs from the vehicle are also optoisolated. A serial port is there to allow simple configuration changes (darkness value to turn lights on, delay for option 1, delay for option 2) that will be stored in the PIC's EEPROM. Other than that, it is a standalone circuit.

I'll start breadboarding the circuit this weekend but wanted to put the schematic out there for people to see and comment on. And I created this thread so we can stop threadjacking the other one.

NOTE: This circuit may change as I physically build it and run into design flaws.

rando · 04-21-2005, 04:37 PM

This looks sweet!

1) Could you use a PIC with a built-in resonator option to save a few parts?
2) Will the linear regulator draw an excessive amount of current while the car is off?
3) Current limiters at the PIC input/output ports connected to the opto-isolators?

Chris31 · 04-21-2005, 04:47 PM

Just some things I found, this what Ill do >>>

1) The MAX232 is not really needed, you can simplify it just by taking the serial port RX line and bringing down voltage to what the PIC is comfortable with. This can be done by means of zener and resistor.

2) No need for TX line, since you wont be reading the configuration stored in the PIC?

3) Use a smaller PIC.

4) Use the SW to emulate a UART if you can.

5) If you can get away with it run the PIC at its internal 4Mhz clock.

6) Use zener/resistor for voltage regulator.

7) No need to opto isolate.

8) The configuration can be done via a button and an LED. This will save you a DB9 connector and a level converter.

Those are just some advice, I know you may not agree with them but those are some possible mods you may wanna consider.

Saab9-5 · 04-21-2005, 04:55 PM

Quote: Originally Posted by rando

This looks sweet!

Thanks. Especially coming from you with all the work you (and Seth, Racemeir, et al) are doing on the AM/FM radio project.

Quote: Originally Posted by rando

1) Could you use a PIC with a built-in resonator option to save a few parts?

Of course. I have a few of these from sample orders I've placed with Microchip. The design is very flexible, only requiring a PIC have: 1 analog input port, 1 serial port, 1 interrupt, 2 digital inputs, and 5 digital outputs.

Quote: Originally Posted by rando

2) Will the linear regulator draw an excessive amount of current while the car is off?

Won't know until I build it. My benchtop power supply has a display for current being drawn so I'll know then and tweak accordingly.

Quote: Originally Posted by rando

3) Current limiters at the PIC input/output ports connected to the opto-isolators?

I'll add those in. Thank you for the suggestions.

Saab9-5 · 04-21-2005, 05:02 PM

Quote: Originally Posted by Chris31

2) No need for TX line, since you wont be reading the configuration stored in the PIC?

Actually I do need the TX line. The circuit will be doing two-way communications, letting you know in real-time what the photoresistor value is. It will have a basic terminal interface.

Quote: Originally Posted by Chris31

7) No need to opto isolate.

I did this to provide a level of safety. But since it will need to operate off of the battery, that will go if the current drain is too much.

Quote: Originally Posted by Chris31

Those are just some advice, I know you may not agree with them but those are some possible mods you may wanna consider.

This is still very much a work in progress but I do appreciate all feedback and ideas.

Chris31 · 04-21-2005, 05:05 PM

No problemo...good luck

jbraddoc · 04-22-2005, 01:39 AM

Wow! I thought you said that you <i>just</i> got into this? LOL... I understand most of it, and it looks awesome :-) I am just glad I finally found someone that knows what I want to do.. LOL

jbraddoc · 04-24-2005, 02:17 PM

I was going to post something, but I closed the window.. it was an edit.. I guess Ill type it all again when I can remember what I said... LOL

Saab9-5 · 04-26-2005, 04:02 PM

The hardware has basically been breadboarded. I'm working on the software now. Unfortunately, I need to take a business trip to New York City so I have to pause this project for a week.

Quote: Originally Posted by jbraddoc

Wow! I thought you said that you <i>just</i> got into this? LOL... I understand most of it, and it looks awesome :-) I am just glad I finally found someone that knows what I want to do.. LOL

Thanks. I'm a quick learner.

Saab9-5 · 04-26-2005, 04:10 PM

Note: The Power On LED in the Power Supply schematic is shown backwards. A new schematic will be posted when I return from NYC based on people's recommendations and any problems I run into while building it.

jbraddoc · 04-29-2005, 03:20 AM

Okay, so here are some thoughts... I was thinking about what my car does, and what I actually want it to do...

For one, the park lights alone at a certain darkness is not needed... I am making a module for my sebring's turn signals for DRLs.. Do not completely get rid of this, because I am going to look something up, and get back on this.

Also, my car has this function called 'Funeral Mode'. Its a way for you to have the headlights on, but still have everything on the dash at full brightness. Would it be possible to be at a certain darkness, like with the park-lamps idea, but have the headlamps on, park-lamps on, and tail-lamps on (DRL off) and Funeral Mode enabled? I will get a wiring diagram, because my car does not use a normal dimmer -- The body computer controls the lighting.

Also, the wire that I call Park / Neutral safety is one wire. It is not two separate circuits. I do not know if that is going to be necessary or not. I would like to have my DRL's enabled when put into gear, but I do not know if it will interface correctly. I think it is just a neutral / ground, right?

And, I was thinking about this... Having a so called pathway illumination from my DRLs in the daytime would be pointless. So I guess remove that.

Umm. Oh, would it be possible to have it where my lights stay on when its dark, after the car is turned off, until 1.5 seconds after the drivers door is opened then shut off? I guess with door trigger, so I am thinking -- Ground? I am going to look in my service manual to make sure...

Umm. what else.... Oh, this one would be an addition, and is for the interior lights. I do not have a courtesy light manual on switch. I have two controllable lights -- map lights in my mirror. Could you make it so when I turn both map lights on, the PIC receives a 12v+ from both (left and right) and sends out a ground to trigger the illumination relay (I think the relay is triggered on a ground)?

I know as I go and think about it, there will be revisions. It is 3 am and I can not think of the rest.

Oh, another one. How much would it cost for you to make this for me since I don't know what I am doing...?

I hope you are having fun with this, and I really appreciate it.

Juliemac · 04-30-2005, 07:49 PM

Intersting. I am using a micro for the alarm system, battery monitor for the power supply as well as other things.
I am using this: http://www.basicmicro.com
They have a nice 40 pin chip with a nice IDE for rapid development.

davesaudio2 · 04-30-2005, 10:14 PM

hmm, the basicatom seems a "bit" expensive to use, suppose it saves you on
a programmer but don't you still need to build your realworld interfaces regardless?

kingtut · 05-12-2005, 10:28 PM

Any updates ?

BAF · 05-15-2005, 08:24 AM

What is a phototransistor / photoresistor for?