picaxe servo stretcher question

[kotori87]

Hey folks, I am developing a fire control computer for Big Gun R/C Model Warship Combat using the picaxe 08M. My question is about standard hobby servos and the range of motion that picaxe SERVO command can obtain from them.

For reference, I use Hitec HS-311 standard servos that, when plugged into a common RC receiver, travel approximately 45 degrees in each direction for a total of 90 degrees travel. I have seen products called "servo stretchers" that read the signal from the receiver, and modify it so that the same servo moves 90 degrees in each direction for a total of 180 degrees travel. For example,
http://www.servocity.com/html/180o_servo_stretcher.html

What I'd like to know is, does the SERVO command provide a similar range of motion?

 

[Wrenow]

Kotori,

The normal range is about 1-2ms pulse. The servo command is certainly good for .75 to 2.25ms. Or, you can do pulsout in whatever length you want. So, if the servo can go that far (mechanically and sensor pot wise) you can certainly do it with the Picaxe.

A quick suggestion - get the 08M based 3 servo controller board to experiment with. The power filtering etc. is already there. You can use the servo outs as inputs as well - what I do with my FCA (Fire Control Assistant).

A trick that works for me: instead of using the servo command, I get the 20ms timing from the radio by relying on the pulsin, then just use pulsouts.

If you are who I think you are, then you know how to get hold of me. I will be happy to give you any information I have gleaned. Feel free to contact me directly, and I will give you my phone number. By the way, there are some things in the archives where the FCA is discussed.

Cheers,

Wreno

 

[moxhamj]

A picaxe would be a perfect device for a "servo stretcher" and would work out cheaper than commercial modules. Just don't try to drive the servo too far but it would be easy to set up a test bed and experiment with values.

I'll second Wrenow's comments about pulsin and puslout.