philUK Posted September 23, 2003 Share Posted September 23, 2003 Thanks for the info, just aquired a 280z tach to try and get it to work with my haltech. I have 2 problems though, one is how do I get the 'guts' out of the metal cradle, have taken off all screws/nuts off the back and it still won't come out. Do I have to use the metal cradle from my 240z to be able to mount it? Also which is the signal terminal. I think it is the 'bullet' type connector on its own, rather then either of the 2 nuts in the white plastic surround. is this correct? I also have a 5v tach output from my Haltech, I have a circuit which increase this up to 12v. but is the 'bridge' over the 30 Ohms resistor to increase the signal voltage, or decrease it. (I'm guessing it would boost signal voltage). Thanks all! Quote Link to comment Share on other sites More sharing options...
philUK Posted September 29, 2003 Share Posted September 29, 2003 please - can anyone help here? - its now driving me mad! Quote Link to comment Share on other sites More sharing options...
Guest d3c0y z3d Posted October 1, 2003 Share Posted October 1, 2003 V=IR If the resistance goes down then so does the voltage... so if you bridge out the 30ohm resistor wouldnt that make the voltage go even lower than 5v ? it would be nice to know how big the second resistor is then you could work out exactly what the voltage increase/decrease is going to be .. you could bypass both and put in a resistor that would give you an exact 12V i take it that the tacho doesnt run 12v .. thats just the signal it takes and then lowers the voltage to what it needs Quote Link to comment Share on other sites More sharing options...
philUK Posted October 1, 2003 Share Posted October 1, 2003 Thanks for the help d3c0y z3d sorry if going back to school here !, but (hope this comes out, grr it takes spaces out) """""""""""""""V2 ____R1___|_R2____| |____V1__________| Where R1 is the 30 Ohm resistor, and R2 is the resistance of the rest of the tach. V1 is the input signal, V2 is the voltage the rest of the tach 'sees', the voltage across the R2 resistor V/(R1+R2) = I V2=I* R2 :. V2 = (V/(R1+R2))*R2 so as R1 decreases the rest of the tach 'sees' a voltage increase. ? So looks like I still need to increase my input signal to 12v even if I bridge the 30 Ohm resistor? is this right? Still can't figure out if I need to get the tach guts out of the metal housing though, and how!?! Quote Link to comment Share on other sites More sharing options...
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