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[Brian60]

I have four linear servo's - go back and forward not round and round like a standard servo. The problem is  they only work on a voltage of 3.5 to 4.2vdc. As my trigger voltage from my PICaxe controller is 6v I'm in a bind.

Can just the signal wire be connected to my controller and a separate supply be run to the servo's from an independent battery? I'm thinking this should be ok.

Next question. As the PICaxe (or even a standard receiver) gives out 6v, what is the signal voltage? I'd hate to connect the servo's to an outside source only to fry them with the signal voltage.

[Subculture]

Picaxe are best run at 5 volts. Also many of the newer generation picaxe chips will run happily on lower volts, alternatively you can gate the output of the picaxe to the base of a small transistor which is connected to a lower bus voltage.

[Jerry Hill]

Seperate battery power should work fine. This needs to be checked as I've not done this for years.

The dedicated positive can go to the servo/s, the neg will also need to go there but a light 'Y' lead needs to run back to the receiver. Easiest route to this is to make up a little harness to sit between the servo, receiver and servo power supply. The receiver can have its own supply through a normal pack.

[Brian60]

Thanks guys. I'll return to this subject in coming weeks once I have the schematic drawn up to explain the setup easier, but essentially the PICaxe is taking one signal from the receiver and converting it into multiple signals to control the four servos in a sequence.

The PICaxe was supplied to me ready built and programmed by someone on another website - I said I'd sit down and learn the programming, but that is for winter months study!

[Jerry Hill]

When the time comes look at what the guys into 'Giant Scale' aeroplanes are doing, they run huge or ganged servos that can not get their power via the receiver because it would blow it, hence have seperate power supplies.

[malcolmfrary]

Seems a very odd voltage range unless they are only designed for use with a 1S Lipo.

[Subculture]

They are designed to run on 1s lipo. Micro model aeroplanes use 1s lipo.

[Brian60]

Correct Malcolm and Subculture, these particular ones are designed for helicopters.

[malcolmfrary]

One of these http://cdn.sparkfun.com/datasheets/Components/General/LM317TG.pdf might be the item to derive a 4 volt supply from your 6 volt main battery.

[david48]

Componants Shop do a voltage dropper board have a look there ,its not very big .
David