Simple help question

driftaholic

okay, this is alittle bit out of the ordinary but im going to use the basic stamp 2 microcontroller board and stuff to control my automatic transmission on my car
other people have done it with switches but im going to do it with this
okay the transmission has 2 solenoids on it and the transmission shifts to different gears with on off combinations of the 2 solenoids


(gear) solenoid 1 solenoid 2
1st gear on on
2nd gear off on
3rd gear off off
4th gear on off


i want to be able to cycle through these up or down without skipping any with 2 buttons (paddle shifters)
so i want to find out a program to put on here that lets me use one switch for up and the other for down to go through the combinations of on/off in order

any help is apreciated
and also how i can wire this little thing into my car
the car runs on 12vdc and this board is 9vdc what would i need to hard wire it in?

thank you all very much

driftaholic

ohh and also the out put for the solenoids has to be 12vdc
so i guess transistors
i know a good amount about electronics but not in depth like this lol

Mike Green

There's a Nuts and Volts column that discusses switching solenoids (and relays and motors) using a Stamp I/O pin. It's #6. Go to the main Parallax webpage and click on the Resources tab. You'll get a list with a link to Nuts and Volts Columns which is the index. #6 is in the first volume. You'll need to have some idea of the amount of current drawn by these solenoids. You may have to disconnect one of them and measure the resistance or put an ammeter in series with it. You'll need a transistor with enough current rating and a high enough gain to switch on with the output current of the Stamp (typically 10-20mA at about 4.5V). Darlingtons are often used. You can also use a MOSFET if you get a logic level one that will switch completely on with a gate voltage of 3-4V.

There have been several threads discussing how to power a Stamp in a car. The simplest way would be to use an LM7809 regulator to drop the 12-15V of the car's system to 9V for the Stamp. There are circuits and suggested filter capacitor values in the datasheet for the LM7809 (do a websearch for it).