Quote:
Originally Posted by Shark Bait
PWM Build - 2nd Stage
Is the 1.95 Volts the 'headroom' voltage that I should expect to see?
When I construct the 4 dew straps and there is a larger load, can I expect to see 0 Volts as a minimum and the maximum voltage achieved when the pot is turned all the way anti-clockwise?
Thanks.
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The 'headroom' voltage referred to probably refers to the fact that when you are using regulators, you are required to supply it with a couple of volts over the regulated voltage. Even when using low dropout regulators, a volt or so extra is usually a good idea - the data sheet will tell you.
The measured voltage at a PWM output depends on the particular circuit. Some PWM outputs will range over a (say) 5% - 95% duty cycle - not necessarily 0% - 100%. If this is the case, then you will get a small voltage at the 'minimum' setting, and near maximum voltage at the maximum setting. In your case, with the LED at max when you have the setting near 50%, it may depend on the series resistor you are using with the LED. The average of the PWM voltage at your 50% setting may be providing sufficient current to fully illuminate the LED.
By the way - you would normally wire the PWM control so that the max output occurs when the pot is fully clockwise.
Good luck.
Cheers
John