MEP 003A Frequency Transducer

[Ray70]

Peter, thank you for the info, I'll take a look those IC's today. Meanwhile, I tried the other circuit on the generator Friday night but found (as I suspected ) that a 4 Hz change at the generator only registered as about 1 Hz change on the meter (the circuit showed a 100uA meter instead of our 200uA) BUT, I had built the circuit with the same 100K 2w resistor that the schematic called for. On my first test board I used 4 100K 1/2w in parallel, which I thought would yield 100K 2w but in fact it is giving me 25K so I'm going to throw that resistor pack back in and see how the gage responds to changes in frequency. Maybe get some of the tach IC's on order as well.

 

[Ray70]

Latest update.... I'm abandoning the circuit I was playing with and have ordered a few of the LM2917 chips. The other circuit will drive the meter at 60Hz but is not giving me any movement on the needle as the frequency changes, no matter what I use for resistors and potentiometers. The only thing that makes it change is varying the voltage into the transducer... That's not what we want! So I'm going to mess around with the frequency to voltage converter chips Peter suggested and see if I can make it work.

 

[massey]

Thanks for your effort so far.

Ed

 

[Ray70]

Ok, so here's the latest. I purchased a couple of the TI tachometer chips that PeterD suggested. I got one hooked up on a bench and got it to drive the HZ gage from an MEP-002A running in essence off utility power using an AC and a DC power adapter. Now the next step is to build a circuit to adapt the generator's 120VAC to the correct low voltage AC and DC signals needed to power the chip. That way the whole thing could be stuffed into the original transducer housing without altering any of the machines wiring.

 

[GREENMV]

Thanks for the update. opcorn: