timed 12v relay for power folding steps

Blessed be those PICs! And the pics showing a quality PCB and layout. I was going to suggest a PIC - maybe even with current sensing (as I intend to do for my newly installed electric windows; mainly for a soft-start circuit for easy precise positioning, but also auto-closing and opening etc). IMO the PIC is usually the simplest and cheapest solution for these somewhat complex applications, but to have a resource like KP to program or supply the circuit is the real clincher. (My year-old SMD PIC-08Ms are still merely soldered to an old 1988 SMD PCB.) Yet again, my compliments KP!

Not a PIC, an AVR! Slight, subtle difference but worth pointing out! Thanks for the compliments. Having proven hardware laying around makes small projects like this much easier.Kevin Pierson

Ah - the stamp or similar... IMO far superior to a PIC, but that's my micro-processing experience that'd make it more versatile & easier. But it's that painful learning curve and hardware hassle that you save people. I hope they realise and appreciate it! I still look forward to my stamp-sized pre-populated $10 PIC PCB with MOSFET etc as my standard hardware for almost any simple implementation - eg, window controls; situational combinational headlight or lamp switching {stop, flasher, reverse, tail, bulb or LEDs); PWM & dimming; alarms and fan controls (off existing sensors), etc etc. But yeah, I have this minor problem with time -cum- priority [Read: I never seem to get that round-tuit!]. I envy your investment, and thank you for helping so many with your AVR & PIC etc solutions.

Good lord Kevin, Hannah's board work is wonderful. BTW My fiend is back in Florida end Jan/Feb/March.

Excellent work and a very elegant solution!  Add my compliments, too! 

The OP will be very satisfied with the results of KP's hard work.

Soldering is fun!

howie ll wrote: Good lord Kevin, Hannah's board work is wonderful. BTW My fiend is back in Florida end Jan/Feb/March.

Have your received the package I sent him last time he was here? I completely forgot about that already!Kevin Pierson

Never got it, probably sitting in his letterbox!

Doh! I sent it out the day we last spoke about it. Hopefully he finds it when he returns. If he doesn't let me know, I'll send another.Kevin Pierson

I hate to state that I am so ignorant with regards to micro electronics that all I see is a board in the pictures, but everything seems nice, neat and clean, just wish I understood this enough to really appreciate the complexity. Having said that, I am VERY appreciative of the work Kevin is doing and its things like this that make these forums worth it and Kevin's willingness to assist shows his and his company’s passion for customer service and satisfaction. It’s these things that give me hope and pride for businesses in this era and wish more companies were as stand up as Kevin.

It's actually a pretty basic board. The "center" is the IC chip - it is an 8 bit microcontroller running at 1.2mhz. Everything North of the microcontroller is related to the 5vdc power supply. These boards use LDO regulators which minimize idle current (each board draws only 2.5mA at idle). The power supply includes a diode for reverse polarity protection. To the right of the IC chip are three separate circuits - two outputs (Q1 and Q3) and one high impedance input (Q2). All three circuits have dedicated drive transistors and necessary base and collector resistors to prevent damage to the transistors from over current situations. In the top right of the board are two diodes, these are to protect the output transistors from back current created by driving inductive loads (and very relevant to another thread on this site) To the left of the IC chip is the adjustable potentiometer that goes to a 10 bit (1023 steps) Analog to Digital converter inside the IC. However, in this application, I am only using 8 bits (255 steps). Because this is an 8 bit controller and because timing resolution is not a high priority, I chose to stick with 8 bits on the converter. Otherwise, I would have had to done 16 bit math which is a bit more complicated and can't be justified by this project. Also to the left is the second input circuit for the other door pin. Like the other input, it has its own transistor and resistors. Like I said, the hardware is fairly basic, it's the software that makes the module work!Kevin Pierson