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Diodes Needed for Back Feed?
- Thread starter Jibebuoy
- Start date
panic mode
- Joined Oct 10, 2011
- 4,864
this is your latching relay info:
coils themselves are not polarized so above document suggests using MOVs as suppression.
if you want to use diodes (cannot blame you), you need to watch polarity....
KC is the common terminal. if you use examples in the document (KC is the negative side), then diodes need to be placed like this:
but since you are using KC as positive 12V, diodes would need to be reversed. like this:
or in your circuit, they would be placed across coils but in such orientation that in NORMAL operation current does NOT flow through them:
same applies when adding clamping diodes to analog inputs. and add some series resistor as well. 1k will do.
finally clamping diodes will cause +5V rail to rise under faults. to deal with that add capacitors. usually 100nF and 10uF will do the trick.
coils themselves are not polarized so above document suggests using MOVs as suppression.
if you want to use diodes (cannot blame you), you need to watch polarity....
KC is the common terminal. if you use examples in the document (KC is the negative side), then diodes need to be placed like this:
but since you are using KC as positive 12V, diodes would need to be reversed. like this:
or in your circuit, they would be placed across coils but in such orientation that in NORMAL operation current does NOT flow through them:
same applies when adding clamping diodes to analog inputs. and add some series resistor as well. 1k will do.
finally clamping diodes will cause +5V rail to rise under faults. to deal with that add capacitors. usually 100nF and 10uF will do the trick.
Last edited:
I am concerned if there would be some stray voltage that might not find its way to ground and will end up finding its way to an MCU pin.
panic mode
- Joined Oct 10, 2011
- 4,864
while at it orient everything so it is easy to read, and make the signal flow from left to right such as
do not turn things sideways, the arduino, +12V power flags and transistors/LEDs circuits look weird.
in KiCad schematics you have not just rotation - things can be flipped using X and Y keys so that connections line up for more readable signal flow. better organized circuits are easy to copy/paste. so applying above, skeleton of this circuit would look something like:
do not turn things sideways, the arduino, +12V power flags and transistors/LEDs circuits look weird.
in KiCad schematics you have not just rotation - things can be flipped using X and Y keys so that connections line up for more readable signal flow. better organized circuits are easy to copy/paste. so applying above, skeleton of this circuit would look something like:
No. Diodes D1,D3 not needed.
