With the source taken care of [Glitch] uses an optoisolator for both protection and level conversion. After working the bugs out of the design he was able to control the relay using 3.3V, 5V, or 12V.

What options do I have? Add a 200Ω series resistor. Resulting voltage and current in economy mode is 3V and 30mA. Add capacitor across resistor. Parallel resistance = 100 * 200 / (100 + 200) = 67Ω. C ...

The standard 555 saturates poorly (2.5V) at 200mA and its reset line (pin 7) is not specified above 15mA, so it is not recommended. The intersil 7555 is a very low power device, so that is not ...

The relay will readily energize and hold at this voltage, but energizing the relay will open the NC contact and remove D4 from the circuit. Removing D4 converts the power to the relay driver from ...

2. The drive-sequence timing controls the solenoid pull-in and subsequent hold operation to conserve power. The V1 timing ramp generated by A3 rises at a rate determined by C1 (pull-in time T pull ...

He uses a triggering circuit based on a 555 timer (PDF). [Rob] mentioned that if you shop around, you can get the relay, 555 timer, and other components for under $15.

A solderless breadboard can be used to wire three of the four building block components together. Also, the discrete electromechanical relay and transistor relay driver component circuits can be wire ...