Evan Purple240zt Posted February 29, 2008 Share Posted February 29, 2008 Quick question! I have a 3bar map sensor with my alky control kit and now need to wire up the 5v source for the map sensor. Should I just drop voltage with a resistor? Does anyone know what size? Grab voltage off of another sensor in the EFI? Thanks guys! - Evan Quote Link to comment Share on other sites More sharing options...
TimZ Posted February 29, 2008 Share Posted February 29, 2008 Quick question! I have a 3bar map sensor with my alky control kit and now need to wire up the 5v source for the map sensor. Should I just drop voltage with a resistor? Does anyone know what size? Grab voltage off of another sensor in the EFI? Thanks guys! - Evan A resistor would not work very well - the supply voltage would then be load dependent and I don't know if the GM MAP sensor's current draw is constant vs its output voltage. It probably isn't. Using another sensor's 5V supply would be a better bet, but you would want to at least check to make sure that you aren't pulling down the supply with the extra load. You probably won't, but you should check anyway. If that doesn't work, you can always roll your own 5V regulator with maybe $15 worth of parts from Radio Shack. Quote Link to comment Share on other sites More sharing options...
Evan Purple240zt Posted February 29, 2008 Author Share Posted February 29, 2008 A resistor would not work very well - the supply voltage would then be load dependent and I don't know if the GM MAP sensor's current draw is constant vs its output voltage. It probably isn't. Using another sensor's 5V supply would be a better bet, but you would want to at least check to make sure that you aren't pulling down the supply with the extra load. You probably won't, but you should check anyway. If that doesn't work, you can always roll your own 5V regulator with maybe $15 worth of parts from Radio Shack. Thanks Tim, Ill probabally do my own regulator since the map sensor is under the dash a fair ways away from the ECU. I am going to make sure the stock boost solenoid wire won't work first. That would be too easy. The regulator seems like a reasonable alternative. Thank you! - Evan Quote Link to comment Share on other sites More sharing options...
Tony D Posted March 2, 2008 Share Posted March 2, 2008 I would do the regulator thing. David Ulbrick drew up a quick schematic for me, I think it's at the Megasquirt sticky... Anyway, it's a solid state device with three leads, power in, out and ground if I recall correctly. It's really bizzare, don't you think, that the Alky unit would not have a +5VDC source plug from it's control box for universal installation? I guess older cars without computer controls are getting to be the exception rather than the norm! Quote Link to comment Share on other sites More sharing options...
Evan Purple240zt Posted March 3, 2008 Author Share Posted March 3, 2008 I would do the regulator thing. David Ulbrick drew up a quick schematic for me, I think it's at the Megasquirt sticky... Anyway, it's a solid state device with three leads, power in, out and ground if I recall correctly. It's really bizzare, don't you think, that the Alky unit would not have a +5VDC source plug from it's control box for universal installation? I guess older cars without computer controls are getting to be the exception rather than the norm! Odd indeed. I ended up grabbing my 5v off of the TPS and it seems to be working fine. I may go ahead and wire up a regulator though next time I have the dash apart. Ill check out the megasquirt thread. Thanks man - Evan Quote Link to comment Share on other sites More sharing options...
Tony D Posted March 3, 2008 Share Posted March 3, 2008 Oh, I missed that you already had a Computer Controlled car! "D'OH!" The internal regulator for 5VDV Vref in the ECU should be plenty for one more sensor. If you have a TPS, like Tim suggested just grabbing +5V from the existing source for the stock ECU should work fine as long as you have the same ground plane for both units. That may not even be that critical, as it's going to read it's own sensor feedback to it's own respective ground plane... Quote Link to comment Share on other sites More sharing options...
Evan Purple240zt Posted March 3, 2008 Author Share Posted March 3, 2008 Tony, no sweat. Thanks for the tip on the regulator. Ill just leave it wired up to the TPS wire since it seems more then one person thinks it would be okay. I have it grounded with my alky kit since the ecu is not actually using it, just the alky kit. Evan Quote Link to comment Share on other sites More sharing options...
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