Digital pot to lower power of 1.25w driver.

• Jan 30, 2014

• #1

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martialmedia

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Has anyone used a digital pot to lower the power of a 1.25w driver? I'm looking to be able to vary the power between 500mw - 1.2w. Any insight would be helpful.

 

• Jan 30, 2014

• #2

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martialmedia

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Looks like this is what I need. DS1809-100 digital pot.

Put this in place of the R200 resistor. http://farm4.staticflickr.com/3677/10860385914_e4cc244f60_c.jpg

 

• Jan 30, 2014

• #3

KRNAZNBOY

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I don't think that is what he wants.......

And you will be able to adjust current going to the diode, not the actual output, with a pot

:beer:
=^•^=

 

• Jan 30, 2014

• #4

ARG

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The way you describe would work, but a better way to to use a driver with modulation input then create a PWM or analog signal to control the power.

Also, check the power going to that resistor, a digitpot may not have a hgih enough power rating. Looks like an 0805 resistor?

Measure voltage and resistance then use (V^2)/R to get power

 

• Jan 30, 2014

• #5

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martialmedia

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Doooh!! You would be correct. I don't think the digi pot can handle it. So much for easy. Looks like a PWM will be required.

 

• Jan 30, 2014

• #6

Cyparagon

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That part wouldn't work anyway, for at least 3 reasons:

VCC for this part is 4.5-5.5V, and your supply voltage will not be in this window.
The value of 100k acts as an open circuit when used as a current shunt as you propose.
Wiper current is rated at 1mA max.