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555 ON 24v Circuit

2015-01-27 07:04  
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555 ON 24v Circuit

If you need to operate a 555 on 24v, you will need to reduce the voltage to less than 18v. The following circuits reduce the voltage to 12v:


If the 555 circuit takes less than 30mA (the 555 takes 10mA) you can use a 400mW zener diode to drop the 24v supply to 12v for the 555. In other words, 12v is dropped across the zener.

Up to 500mA:

The next circuit will allow up to 500mA. The transistor will need to be placed on a large heatsink. It isan emitter-follower-regulator transistor and can be used with a 400mW zener. The output voltage is 0.6v lower than the zener voltage.

Up to 500mA with "Amplifier Zener"

A 400mW zener can be converted to a "Power Zener" by combining with a transistor as shown in the following circuit: 12.6v will be dropped across the rails. In other words, if the top rail is 24v, the bottom rail will be 11.4v.

Up to 1A:

Using the next circuit will allow the 555 to take 200mA and the load to take 800mA. The 7812 will need to be placed on a large heatsink. The 7812 is called a 3-terminal VOLTAGE REGULATOR.

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