Using a CD4053 to switch voltages

Other Hardware General Electronics
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Analog switchs are for signals, not power, they have a lot of resistance.

Just switch the rails with transistors - the 5 to 6.25 change might be best done with a programmable
voltage regulator like a 723, you could just switch the feedback resistor divider for that.

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Hi;

jaskamakkara:
Quick question, if I'm using a basic linear regulator for the 12V -> 6.25V conversion (I'm using an LM317LZ), can I switch R2 to give me 5V out somehow? So if I have one resistor to give 6.25V out and another to give 5V out in parallel that I can switch between?

Yes, switching like that will work, just switching another resistor in parallel with another to change output voltage.

You would use a switch in place of the transistor.
Tom... :slight_smile:

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You might get some design ideas from this:

Serial Eprom Programmer - Steve Ciarcia

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jaskamakkara:
Thanks Tom, can I use 5v signals from the Arduino in combination with those transistors instead of a physical switch? Since I only need two voltages, could I hook one transistor up to a digital pin, and the other transistor hooked up to the same pin through a NOT gate?

I'm looking to have no moving parts, only MCU control, and I want to keep the component number small.

Yes you can, you will need base series resistors.
The link from @pwillard is a good example of a universal programmer.
Tom... :slight_smile:

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jaskamakkara:
Excellent source, thanks!

Thanks for your help! I'm assuming a 120Ohm base resistor is enough for an Arduino digital pin?

Another question:

If R4 (in your circuit diagram) sets the max voltage, can I just use one transistor to give me a switch between 6.25V and 5V?

Yes, you can do that. I think you can do it better - intead of placing R5 in parallel with R4 you may place them in series and connect Arduino pin between them. If the pin is in high impedance mode (INPUT) controlling current must go through both R4 and R5. When you switch to OUTPUT LOW, current goes only through R4 to the Arduino pin and so you bypass R5 and get lower output voltage from the regulator.

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Yes, this is what I mean. It works only for low voltages, when the pin is in high impedance state the voltage should not exceed supply voltage of Arduino (5V). It is usable when you only want to switch between 5 and 6.25V.

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