im getting rid of my computer on my 92 rs how can i keep my electric speedo working? thanks

 

Do you have the Helm manual for your car? That will be a big help. Basically you need to check the VSS buffer's output, and see if the signal is just split off.....one to the computer to control various engine properties, and one to the speedo, or if the computer is the driver for the speedo. If the computer is the driver, you have to remake the driver, or see if anyone has already done so. Otherwise, the digital portion comes in....you'd have to design a flash frequency counter (realtime or as close to it as possible)....probably using an op-amp in comparitor mode looking for 0's) Count the frequency, knowing that your speedo buffer wanted 4000 pulses per mile (or 2000 depending on your cars speedo) Divide down...probably easiest to use a small microprocessor, but then you'd need to learn the Assembly for it, and have a prom burner to make a prom to hold the program on. Once you have it in a say, an 8 bit format (making the max speed it would count be 256, after that it would cycle to 0) you'd need a decoder circuit to drive 2 seven segment displays, and 1 2 segment display (for that 1 on the side of the digital speedo) If you don't have a digital dash, I would guess that the way the analog ones work is basically on a varying voltage level, so again, get that 8 bit number out to an Digital to Analog Converter (DAC) and use it to drive the speedo. The problem that arises is you would need to know the max voltage for the speedo, and the minimium voltage, and thats assuming the speedo is linear in nature (i.e. to move the needle 1 mph would require say 10mv all the way whether you were going 10, 50 or 100 mph, but it might increase. It could theoretically be a ton of work....there might be one made, but I wouldn't have the first clue where too look....definatly not for the faint of heart.....probably easier to convert to a mechanical speedo, I think dakota digital makes a electronic to mechanical box.....they might even have something in there for doing the above.....other than that....look into aftermarket speedos lol