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Topic: Capacitor discharge unit for solenoid (Read 2237 times) previous topic - next topic

_kuroo

I'm not sure if this is meant to be here or in the general electronics section. but oh wells

Can someone point me in the right direction on how to make a capacitor discharge unit to make a solenoid kick?? or should i try another approach. im definitely not sticking batteries in parallel/series. i need to save space and weight.

jackrae

#1
Feb 28, 2012, 07:38 pm Last Edit: Feb 28, 2012, 08:48 pm by jackrae Reason: 1
Fairly easy to do once you understand what's required.

Taking it in stages,first consider the capacitor as the secondary energy source.  Charge the capacitor continuously via a limiting resistor. This resistor needs to be of quite high resistance as will be explained later.

Across the capacitor you fit the solenoid in series with an scr.  When you pulse the scr, it is driven into conduction and discharges the capacitor via the solenoid.  Once the capacitor is fully discharged the scr switches off.  However, if the charging resistor is of too low a value the capacitor will never fully discharge and the scr will never turn off.

Once the scr is turned off the solenoid is released and the capacitor is again recharged via the limiting resistor.

The above technique is/was used in some designs of intrinsically safe solenoids since the line charging current could never rise above 20ma (the normal IS limit) which was set by the limiting resistor based on using a 24 volt supply.  By this means solenoids with wattage rating far in excess of normal acceptable limits were possible.  Note that all components (resistor capacitor and SCR were all "potted" as part of the solenoid coil).

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