What parts would be required to activate a circuit once ...
09-11-2003, 11:41 AM
#1
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What parts would be required to activate a circuit once ... I want to install an electronic TPS switch.... (tap off the lead on the PCM) ... my question is, what parts would I need to build something that when 4.5 volts is hit would allow the circuit to activate?
09-11-2003, 05:05 PM
#4
Re: What parts would be required to activate a circuit once ... Are you looking for the unit itself, or the parts to build such a circuit? If you are into building your own circuits, you could use an LM339 comparator IC or a general purpose OP amp like a LM324. It would be a pretty simple circuit to wire yourself; just the IC and a couple resistors, and maybe a transistor to drive the output depending on how powerful the output needs to be. All parts available from Radio Shack!
09-11-2003, 05:43 PM
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Re: What parts would be required to activate a circuit once ... The LM339 works poorly at the upper end of its
common-mode range, and with only 5V supply that's
getting into it (it wants 2 Vbe or more off the
upper rail). But there are plenty of 5V CMOS
rail-rail op amps around that would do fine.
Or, if your threshold is a little more crude,
a single PNP and two resistors would at least
give you a sensible digital output (low = go)
at about a 4.3V trip point.
Then again, people sell reed switches that use
the actual mechanical position (imagine that,
sensing throttle position directly). Depends on
whether you like your clutter on the engine or
under the dash.
common-mode range, and with only 5V supply that's
getting into it (it wants 2 Vbe or more off the
upper rail). But there are plenty of 5V CMOS
rail-rail op amps around that would do fine.
Or, if your threshold is a little more crude,
a single PNP and two resistors would at least
give you a sensible digital output (low = go)
at about a 4.3V trip point.
Then again, people sell reed switches that use
the actual mechanical position (imagine that,
sensing throttle position directly). Depends on
whether you like your clutter on the engine or
under the dash.
09-11-2003, 07:16 PM
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Re: What parts would be required to activate a circuit once ... A MC33072 single voltage rail to rail op amp would work well. You could make the trip point adjustable with a multiple position DIP switch and differant value resistors. If you are into electronics check out the FREE circuit simulator from Simetrix. http://www.catena.uk.com/
You can get the Spice model for the MC33072 op amp from http://www.onsemi.com/site/products/searchliterature/0,4425,,00.html
Too add spice models to the program you simply start Simetrix and drag the file(using windows explorer and mouse) to the main window of Simetrix and it auto installs. If all of this is over whelming I can put together a simple schematic in a few days. Send me a PM if you are serious about building one. It wont take much time but I have a busy schedule tonight.
You can get the Spice model for the MC33072 op amp from http://www.onsemi.com/site/products/searchliterature/0,4425,,00.html
Too add spice models to the program you simply start Simetrix and drag the file(using windows explorer and mouse) to the main window of Simetrix and it auto installs. If all of this is over whelming I can put together a simple schematic in a few days. Send me a PM if you are serious about building one. It wont take much time but I have a busy schedule tonight.
09-11-2003, 11:22 PM
#7
TECH Senior Member
Thread Starter
Re: What parts would be required to activate a circuit once ... Thanks guys! :beer: I'm looking to build this circuit myself... I figured it couldn't be that complex, and the ones I've seen from NX or other places seemed kinda high priced for what they do...
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09-12-2003, 09:09 AM
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Re: What parts would be required to activate a circuit once ... On the other hand, if you ran the LM339 off the
battery it would have no problem with the TPS
signal range (you would want to make threshold
off the 5V though, so as to track TPS supply).
This would have the benefit of being more able
to drive other 12V stuff; hang a resistor & NPN off the '339, and the NPN can drive a relay coil,
etc.
battery it would have no problem with the TPS
signal range (you would want to make threshold
off the 5V though, so as to track TPS supply).
This would have the benefit of being more able
to drive other 12V stuff; hang a resistor & NPN off the '339, and the NPN can drive a relay coil,
etc.
09-12-2003, 12:02 PM
#9
Re: What parts would be required to activate a circuit once ... Right, that's what I was sugesting, running the LM339 off the 12 volt battery. And I would probably use a power MOSFET on the output to drive a relay coil etc., they are newer technology and do very well driving inductive loads.
Hey this is great to see so many electronics savy people on this board! I'm an electrical engineer, but I don't expect all car people to know electronics this well!
Hey this is great to see so many electronics savy people on this board! I'm an electrical engineer, but I don't expect all car people to know electronics this well!
