Hello all, I'm trying to convert an old mechanical speedometer over to electric using parts scavenged from a modern gauge cluster and I"m at my wit's end with this circuit. I purchase a CS8190 air core driver and am trying to use it to drive the air core "motor" I pulled from the modern cluster. I originally tried using the control board from the new cluster, but it would not fit on the back of my gauge and I could not get it to scale correctly. Anyway, I have tried building this circuit on a bench and testing it with my variable power supply and function generator and am stumped and getting frustrated. I've built the sample circuit on the datasheet (http://www.onsemi.com/pub_link/Collateral/CS8190-D.PDF) and simply cannot get the gauge to function. I've double and triple checked all the connections and have built it both on a breadboard and PCB but have had no luck.
Originally I found I had an issue with my input as the sample circuit uses a 10k input resistor and filter capacitor (at least I assume this is the capacitor's function). My function generator will only drive a 50 ohm load, so for the purpose of testing I have eliminated both the resistor and capacitor on the input signal. When scoping the pins on the chip I get a good clean signal on the FREQin pin and am also getting a clean buffered square wave out on the SQout pin as is supposed to happen. I've also scoped the CP+ pin and appear to be getting a signal similar to figure 8 on the data sheet. However, no matter what I try I the F/Vout pin is not varying at all. This pin is supposed to vary from 2 to 6V (per the datasheet) based on the input frequency, but it's not budging at all. I initially thought it was just a bad chip and tried a second one, but am having the same problem. Does anyone have any ideas? I'm just exhausted of sitting in front of my workbench trying to get this stupid needle to twitch. Is there something I'm missing? I'm not sure how else to test this circuit.
Originally I found I had an issue with my input as the sample circuit uses a 10k input resistor and filter capacitor (at least I assume this is the capacitor's function). My function generator will only drive a 50 ohm load, so for the purpose of testing I have eliminated both the resistor and capacitor on the input signal. When scoping the pins on the chip I get a good clean signal on the FREQin pin and am also getting a clean buffered square wave out on the SQout pin as is supposed to happen. I've also scoped the CP+ pin and appear to be getting a signal similar to figure 8 on the data sheet. However, no matter what I try I the F/Vout pin is not varying at all. This pin is supposed to vary from 2 to 6V (per the datasheet) based on the input frequency, but it's not budging at all. I initially thought it was just a bad chip and tried a second one, but am having the same problem. Does anyone have any ideas? I'm just exhausted of sitting in front of my workbench trying to get this stupid needle to twitch. Is there something I'm missing? I'm not sure how else to test this circuit.
