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Converting feeder to external power
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scribble:
I have a Surepet pet food bowl that has an automatic lid that keeps the food covered to keep flies off.
It uses 4x "C" batteries in series which only last a month or so, so want to convert it to external power.
It has 3 illuminated buttons and when it's first turned on they normally light for about 5 seconds then go out and the device will then respond to movement/shadows.
I connected up a bench supply set to 6v, turned the device on and the buttons just stayed lit for about 10sec, went out but it won't respond to triggers or button presses.
So I disconnected the leads from the bench supply and connected up to 4x "C" in a series string just sitting on the bench and the feeder boots and works correctly.
I put a meter in series and it draws around 30mA normally and about 200mA when opening/closing the lid, so nothing the bench supply can't handle.
I've tried multiple non-battery power sources of various voltages between 5-6v but none work, only the batteries will.
I can't understand why it won't work on an external supply?
johnkenyon:
Check the wiring of the battery compartment.
Are you sure that the thing takes just a 6v supply?
Is there an extra wire which goes to one of the intermediate contacts?
For example, it might have 3 wires - zero volts, 4.5v, 6v with 4.5v feeding the movement sensor, and the 6v connection going to the motor/solenoid that opens the lid.
scribble:
As far as I can tell it's just 6v (or there abouts, 4x C cells) as I can connect the 4 batteries in series outside of the battery compartment and feed that to the +/- contacts inside the compartment and it works fine. Take the same hookup wires and connect to a 6v power supply and it doesn't complete the boot process.
Bratster:
How much current is the power supply you are using rated for?
My guess would be the feeder draws a large spike of current when it powers up and the power supply can't handle that and dips down in voltage.
That maybe too fast to see with a multimeter, you would need a scope.
You could also try adding some large capacitors to the output of the power supply and then try turning on the feeder and see if that makes a difference.
you would turn the power supply on with the capacitors connected so they will charge up, and then you would connect the feeder after they are charged up.
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ejeffrey:
Some battery powered device can be super sensitive to EMI. This can be because of sheer laziness or because the use some very high impedance sensors. Try hooking up to batteries but connect the negative terminal only to your psu ground. If it fails then the problem is EMI. Otherwise probably transient power draw.
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