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Thread: Simple voltage regulator ideas

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    Default Simple voltage regulator ideas

    I am after ideas for a simple variable voltage regulator for testing vintage electronic watches.
    Requirements are:
    Adjustable between 1 volt to 2 volt max current 50 microamps. Input would probably be a 9v battery.

    Tony



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    If you only need 50uA, maybe a 1k pot across 2 x AA batteries and get the output between the wiper and GND?
    It won't have active regulation, but at around 3mA discharge, it will take a long time to drain the batteries to make a difference to the voltage output to the watch

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    And if you want a fine adjustment, you could always use a multiturn trimpot

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    It'd be a case of defining the word 'simple', and there are many different kinds of simple -- a pair of 1.5v batteries with a voltage divider circuit as ammilion explains is simple, but you need choose your resistors carefully to limit current and remove the possibility of the circuit being able to apply more voltage than required (a SMD 2v zener to clamp the output).

    Simple could be too simple if you want this regulator to -limit- the possible current applied to the device...I mean, just as a testing pragma one likes to limit and measure the current (if any) taken by the device.

    If this were a consideration and I kept the 9v battery in the picture, I can form a mental picture of a circuit involving a dual op-amp package like LM358 or similar...9vdc to power the chip and wee 78L05, output of this to variable resistor divider network, to use one opamp as the adjustable voltage source (done proper, a reference voltage source, zener or whatever would be attached to the non-inverting input), and this output then goes to second opamp configured as a voltage follower/5ma constant current source.

    On the other hand with a 9v cell, simple might be this --> ...if you like to hack, you can check the datasheet for the IC and what they've done on the board with the trimpot, and rework it to limit the output voltage range to the 1 -2 volts you require...and use something like a 56k resistor on the output to limit the current to <5ma.

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