R G Keen polarity reverse circuit

[iampoor]

Anyone built this?
Wondering what some good starting points would be for resistor values.
I tried building the circuit with all 10k resistors (including the voltage divider). Works fine when the switch is open, but the signal disappears when the switch is closed. Hmmmm

http://www.geofex.com/article_folders/polarity_reverser/polarity_reverser.htm

[induction]

I haven't built it myself, but this has been verified by several people. Take a look at the last op-amp stage.

[iampoor]

I haven't built it myself, but this has been verified by several people. Take a look at the last op-amp stage.

Cool, thanks! I will try building it with a larger bias resistor, and a low value voltage divider. I cant imagine a TL072 would have any issue with me using 10K resistors. Woner why they went with 220k's in that schematic. Hmm.

[PRR]

> Anyone built this?

It is a well-known plan and I have seen it used.

> Woner why they went with 220k

Switch open, input impedance is just Rbias. Switch closed it also has R1. However if you used all 10K, that only means a drop from 10K to 5K, not no-signal.

> signal disappears when the switch is closed

Build error. Start with DC voltages to check for basic flaws.

[iampoor]

> Anyone built this?

It is a well-known plan and I have seen it used.

> Woner why they went with 220k

Switch open, input impedance is just Rbias. Switch closed it also has R1. However if you used all 10K, that only means a drop from 10K to 5K, not no-signal.

> signal disappears when the switch is closed

Build error. Start with DC voltages to check for basic flaws.

Thanks Paul. I will look it over again!