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If a schematic requires a polarised capacitor but I don't have any... can I use a non-polarised capacitor and a diode?
If a schematic requires a polarised capacitor but I don't have any... can I use a non-polarised capacitor and a diode?
Why a diode ? A non-polarized capacitor is just like a polarized capacitor except it doesn't explode when connected in reverse. So yeah you can use it without any circuit difference. Note that unless it's a ceramic cap, a 10uF non polarized film cap is likely to be 3x the size of your entire board...
Repeat : do not put a diode.
In the circuit you linked to both C2 (.1 uF) and C5 (10 uF) are used as decoupling capacitors. You may want to give this a read to understand their purpose. The merit to using a polarized electrolytic is that they lend themselves to getting more capacitance in a smaller package. That was mentioned already in the thread. Also as RCinFLA mentions, for your application you could use a non-polarized capacitor but good luck finding a 10 uF one as it will be big. The reason for C2 is to remove any power supply spikes and prevent false triggering in your circuit. The reason for C5 is primarily to maintain a constant voltage to your circuit.
Also, on a side note the drawing of the USB connector is incorrect as the Data + and Data - are in the center with V+ and V- (GND) on the outboard sides. Just don't go by things as shown for the connector.
Why on earth would you buy no-name-brand junk???
I think Maplin sells junk in England but I am in Canada so I buy good quality electronic parts from Digikey or Newark.I have only bought one single pack of capacitors before from Maplin. I don't know any "names".
Any to recommend?