LM339 comparator woes

[hylaster]

Hello all. I'm working on a FSR touch CV controller. I am hoping to have trigger outs from a couple of the touch pads as well so I am using an LM339 in a basic comparator circuit.

According to the data sheet, this should be pretty straightforward. The reference voltage looks good - in this case around 3v, and the input voltage from the FSR looks right too. But I'm getting full voltage at the output without applying any pressure., Applying pressure past the reference voltage has no affect. Does anyone have any experience using th LM339 in this application?
Thanks!
chuck

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[State Machine]

Well, if the REF is +3V (V-) and the Vin is grounded (V+), and the output is pulled up to Vcc via a resistor and you are still getting Vcc at the output, then the comparator is probably bad assuking Vcc and ground are properly connected.

That output should be saturated and pull the putput pin to 0V ideally. Do all sections of the comparator do this? Also, don't leave any other inputs on the other comparator sections floating and bypass the Vcc pin to ground with a 0.1 uF capacitor.

BTW: Can you show the entire circuit schematically for us?

Bill

[hylaster]

Same thing happens on all four comparators. FWIW - I have tried 3 different chips and 2 breadboards, so this must be user error.

I am using a 9v battery for power. See the attached, poorly-drawn schematic. In this version REF is more like 4.5v, after a voltage divider between the +9v and REF input.

All unused input pins are tied to ground. I am not sure what you mean by grounding Vin as there is only an FSR (two pins) between it and +9v.

Thanks for the help!

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[blue hell]

[State Machine]

I second that Jan

Bill

[hylaster]

That was it! Thanks so much.

[State Machine]

Hylaster, to electro-music BTW !!!

Bill