voltage needed for pwm input of servo?

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Though this question is slightly off topic - I figure somebody here would probabaly know. I've made a couple of 5V AVR boards that control hobby servos that have 6V supplies. But what about 3.3V? On a system I'm working on I was going to have 3 primary supplies - 3.3V, 5V, and 6V - 3.3V for an ARM, 5V for AVRs, and 6V for servos. But while thinking about how to simplify the board I realized I could probabaly drive the AVRs with 3.3V. The only possible problem I can see this causing is that maybe the 3.3V signal wouldn't be high enough for the servos. To be safe I could put in transistors on all the 3.3V servo outputs - but that would be alot of transistors and probabaly defeat the whole board space saving idea...

So - anybody know if a 3.3V pwm signal is enough to drive a standard hobby servo? Thanks!

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3.3v should be fine for a servo. You could probably go lower, this will however be determined by the servo that you use. If you want to test it simply use a simple voltage divider connected to your output pin and start low and work your way up till the servo responds.

-Curiosity may have killed the cat
-But that's why they have nine lives

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JChristoff
Illinois

Last Edited: Wed. Jan 12, 2011 - 02:13 AM
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Maybe a driver like Microchip´s TC4420 (or similar) is good.
They can work with 3.3V levels and output 4.5...18V with some amps, are relatively cheap and you can buy it at farnellinone

Klaus
********************************
Look at: www.megausb.de (German)
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I have had no problems driving the signal input of servos from 3.3V AVR:s. My servos are all quite new, I guess there could be problems with older servos.

Edit: Just noticed your servo supply voltage is 6V. This is not the case for me since my servo supply is 5V from BEC (in a speed controller) or 4 x NiCd battery.

/Lars

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Hmmm since nobodys tried it out - I'll have to give it a shot later today. Will report back my findings.