Isolated dual power supply from 5V

This is a unregulated supply for low power circuits. You may be able to regulate the outputs with zeners or small regulators like 78L05. The transformer can be hand wound in a mini ferrite pot core. you can use 2N2222 or any other fast transistor. The transformer should have 1KV isolation. The dot polarity of TR1 should be properly observed, else it may fail to oscillate or give output. Diode should be fast recovery type, for less than 100mA use 1N4148. transformer, pri-20-20, sec-60-60, a SWG-AWG to suit the current you design for, any fast switching transistor would work, no Read More …

 
Drive SCR thyristor with 555

This circuit gives a burst of pulses to fire 2 SCRs, when pin 4 is taken to 12V the SCR is turned on, to use this circuit you need 12V short pulses phase shifted with respect to AC sine wave on bridge, like this you can control the bridge from near 0% to near 100% ON, That way battery banks can be charged, electroplating can be done, current and voltage can be controlled with opamps, thyristors are very rugged compared to transistors and MOSFETS in that order. Edit the circuit eagle cad file del00015.zip, eagle cad has a free version Read More …

 
Pulse width modulation using 555

IC1 astable gives a fixed square wave at pin 3, C1 and R1 derive uS trigger pulses from IC1 and this will trigger IC2 monostable or single shot, the voltage at pin 5 of IC2 will change the pulse width output of IC2, to get it working all the three RC combinations have to be figured out. You can even build a small SMPS with this or even control the temperature of your soldering iron using the SSR solid state relay circuits in power section, then you need to think and design the cycle time of a soldering iron heat Read More …

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