Basic Stamp controlled Truck Starter

switch

hey everyone,
I want to set up a basic stamp 2 to start a chevy truck at the touch of a button, has anyone here ever done that
and would you mind posting your expeirences w/ that? Also i know i need a 12v relay, but i have no clue what
kind of amprage it would need to handle.
Thanks

-Switch

Chris Savage

Switch,

·· I attempted this task once.· I got the idea from a magazine project and set out to try it myself.· What I will do is tell you what you need to do.· You will have to figure out how to implement this.

·· First of all, the ignition system needs to be active.· Normally this is done when you turn the key to ON in your vehicle.· In my application this didn't matter since the computer also controlled the ignition.· Anyway, you have to use an Automotive relay ([url=mailto:12V@30-40A]12V@30-40A[/url]) to control the starter relay.· This will get the starter motor turning.· While this is happening you have to be monitoring the tach signal for pulses indicating the engine is running, at which point you disengage the starter relay.

·· The exact RPM rate you will be looking for will vary some, but basically I did a test-run to see what I was getting during a normal start.· A safety feature you should implement is that is the engine doesn't start within a specified time, to shut down the system.



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Chris Savage

Parallax Tech Support
csavage@parallax.com

switch

Alright thanks, here is the situation:
We don't want a key ignition (security is not high as this is a mud bogger plus there might be a keypad in the project as well to access the different functions) so we want a switch that brings acc high as well as brings the bs2 online. Then when the bs2 gets the button press for engine start, it runs a relay to the starter relay until the bs2 sees nominal pulses on the tach line? Then it turns off the starter relay and the sequence is complete. This is an old truck and i'm not familiar w/ how tachs get their signal, generally do they have an electrical connection for the tach to the engine?

Paul Baker

If your truck still has the key ignition and you want it removed and replaced by Stamp control, you can do what car thieves do and bypass the ignition key. Then when the stamp controlled relay activates, it will start the truck regardless if the key is in the ignition or not.

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switch

thanks paul and chris, pretty much the key ignition was damaged and were to lazy to replace it plus this will be way cooler [noparse]:)[/noparse]

Chris Savage

·· As for the Tach pickup...You can buy one, build one, add a magnet a hall-effect sensor.· There are actually quite a few ways this could be done.· Ideally the ignition coil would provide a TTL pulse to the Stamp, but in reality what you have is a wire with about 20,000 volts running through it that you want to monitor for the spark signal.

·· In my application the ignition coil did have a tech pick-off circuit.· Not TTL, but easier to interface than the full spark signal.· I don't remember the specifics, except it took days to work out.· Try a google search for, "inductive tach pick."

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[noparse][[/noparse]color=blue>Chris]
<FONT face="Times New Roman" color=#0000ff>Parallax Tech Support[noparse][[/noparse]/color]

[noparse][[/noparse]color=#0000ff><a]csavage@parallax.com</A>[noparse][[/noparse]/color]

steve_b

A coil and RC filter would probably be about it.· Run that in to a mini-LED and then to a photocell.· Not only does it offer protection, but it gives a nice troubleshooting light that would give indication if a certain cylinder is firing.

If you do a google on Fox & Hound wire tools, you'll find what is basically an inductive pickup with a speaker connected to it...if you are searching for one wire amoung a hundred, you attach a 'warbler' that will put a 1kHz signal on the wire of interest and the 'detector' (inductive pickup) will be passed across a mass of wires and you can pick up the signal.

If you put it across an AC line, you will hear the 60Hz and likewise near any motors and flourescents (from the ballast).

I'm sure someone knows a quick link to inductor winding and how many 'wraps' you would need to pick up a given signal (the more wraps the more signal you get...I think! lol· been a while).

Do that or the hall effect sensor is good!

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·

Steve
http://ca.geocities.com/steve.brady@rogers.com/index.html
"Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."

switch

would i put a magnet on the needle on the tach, and then when it passes over the hall effect switch thatd be the signal? sounds like the easiest method.
thanks for all the input, ill post my proj when its done to give yall a look.

allanlane5

A magnet on the needle on the tach is probably the hardest, least reliable way to do it.

All you really need is a couple of wraps of wire around a spark-plug-wire, with a resistor tied to it. When the spark current goes through, it will inductively couple to the wire wrapped around it. You may have to experiment a little to insure you're not getting too large or too small a signal. O'scopes are very good for this.

switch

oh thats right, becuase spark plug wires generate a current field when they fire and thats why you can have premature cylinder firings if your plug wire is damaged cuase the field will set off the adjacent plug. thanks allan

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