Lookin for a cheap reliable pressure switch.

boostjunkie · Post by **boostjunkie** » Wed Apr 14, 2004 3:24 pm

I'd need a switch that can sense a pressure differential between the outside of the airbox and the inside of the airbox. 21st Century Performance suggests a sensor accurate enough to measure a 2inches of water pressure differential.

The book gives a vendor with the appropriate switch but they're located in Australia. I'd rather find something a little closer to home.

I'm trying to have a switch that measures the flow of the airfilter with a switch that sounds an audible alarm when the filter has a sizeable reduction in flow.

Any help would be greatly appreciated.

THAWA · Post by **THAWA** » Wed Apr 14, 2004 3:27 pm

http://www.mcmaster.com/asp/DisplCtlgPa ... Width=1072#.

something like that?

boostjunkie · Post by **boostjunkie** » Wed Apr 14, 2004 3:43 pm

The second one listed seems like something I can use, however, I'm curious about the listed temperature range:

Temperature Range:
Ambient: 30° to 160° F
Process: -10° to +200° F

Which one would be the operating range?

vrg3 · Post by **vrg3** » Wed Apr 14, 2004 5:10 pm

Um, it's also for the extremely wealthy.

I mentioned this in the other thread, but -- go to Crazy Ray's, grab two identical MAP sensors from wherever you wish (two GM cars would be the easiest since they're near the entrance and I do believe they all use the same transfer function

), and check back with me after I've drawn up the circuit you need.

boostjunkie · Post by **boostjunkie** » Wed Apr 14, 2004 5:16 pm

SWEET!! I get to go to Crazy Rays again!!

I'll bet gettin in touch with you vrg3, after I pick up some MAPs.

vrg3 · Post by **vrg3** » Wed Apr 14, 2004 5:53 pm

'kay, something along these lines:

http://www.graphics.cornell.edu/~v/pics/diffpress.png

BAC5.2 · Post by **BAC5.2** » Wed Apr 14, 2004 6:21 pm

Ahh, I see you decided to use a coil-y thing near the triangle. Very nice...

vrg3 · Post by **vrg3** » Wed Apr 14, 2004 6:42 pm

Actually, I decided to use the triangle near the coil-y thing. That protects the transistor.

boostjunkie · Post by **boostjunkie** » Wed Apr 14, 2004 6:50 pm

I know I've said this many a times, but it deserves saying again. You're the man!

Also, here's the instructions on how to disable that reverse beeping noise:

SOURCE:
http://www.celica.net/techarticle7.asp

...

Reverse Beep Removal - By Phil C

Tools Needed :
Short handle #2 Phillips screw-driver
Wire Cutters
Electrical Tape
Digital Multi-meter or 12-volt test light

How To Do It :

You will be removing the instrument cluster from your vehicle to get rid of the beeper. Your first step is to remove the dark grey trim ring. It is held in by 2 phillips screws located at the top of the piece about two inches to the right and left of center. You'll need a short screw-driver to reach these screws. Once the two screws have been removed gently pull the trim piece towards you. It should pop out easily. You can now see the three screws holding the instrument cluster in place. Two on the bottom at either side and one at top right of center. Remove all three. Now pull the instrument cluster towards you, the steering wheel is in the way so you will have to do some twisting and turning to get it out. I was able to pull it far enough to the right to access the wire harnesses. There are two harnesses on the back of the cluster, a white one and a smaller light blue one. Remove both by pressing the clip down and pulling gently. Set aside the instrument cluster. Now look at the white harness. When the clip is at top you are looking for pin 21, second from the right on the bottom row. You can use a multi-meter or 12-volt test light to verify this by turning the car on and putting it into reverse. Pin 21 will go hot when the car is in reverse. For information pin 7 and 8 are ground or you can use the steering column brackets for ground. Turn the car back off. Now that you have verified that you have the right pin turn the harness over to get to the wires. Cut the wire to pin 21. This is a red with a black stripe. I covered both severed ends over with electrical tape to prevent any shorts from occuring and put everything back together. You've now gotten rid of the single most annoying thing about this vehicle.

I would like to hook up the pressure switch through another toggle switch so I could override the beeping noise once I knew the filter was dirty (the chances I would change the filter right away are negligible, and I couldn't imagine listening to that beeping constantly until I changed the filter!!).

vrg3 · Post by **vrg3** » Wed Apr 14, 2004 10:48 pm

Huh. You might be able to simplify things, then. You could try scrapping the transistor and relay, and instead connecting the output of the second op amp straight to the gauge cluster at pin 21:

http://www.graphics.cornell.edu/~v/pics/diffpress_2.png

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Lookin for a cheap reliable pressure switch.

Lookin for a cheap reliable pressure switch.