Tal100rs, motor focus

[nightfisher]

A while back i mentioned i was making a servo focuser for my tal, this morning i decided to see if i could finish it, took about forty minutes to get it in position, and hey presto it works so well.

This is not my idea, i think credit must go to bizibuilder for giving me the idea, it utilizes 2 radio control servo`s with a couple of modifications internally, then linked together, by turning one servo the second follows it, so this idea requires no battery's to power it

hope you like it

[libraryman]

piccy's ?

Ray

[nightfisher]

pics done now, forgot to upload them in my excitement, its a lttle untidy so i might go for a mk11 mounting as an when

[nightfisher]

thought more people would be interested in this project

[AndyH]

-Is the other servo at the end of the cable? And you turn it, which turns the one closest to the scope servo??

Andy.

[nightfisher]

-Is the other servo at the end of the cable? And you turn it, which turns the one closest to the scope servo??

Andy.

Yes Andy it is, when i fitted the wiring i used a servo extension wire to give me a plug an socket so i could easily detach the hand servo, when the pair of servo`s are modded this way by removal of the mechanical stop and the potentimeter circuit, they give continuous 360 movement, i added the pulley belt to the focus shaft as the belt did not grip the tal focus wheel to well, the gearing ratio works just right with the tal crayford, overall im very pleased

[AndyH]

I don't get the 'no batteries' bit?? I'm probably being very dense, but how does it work with no power?

[Gina]

I don't get the 'no batteries' bit?? I'm probably being very dense, but how does it work with no power?

Ditto!

[nightfisher]

i thought the same when i first came across this idea, the hand held servo when turned acts as a simple dynamo, generating dc current, direct to the focus mounted servo, bear in mind that the dynamo servo is geared, so that when turning the top, the motor inside turns much much faster, simple but effective

[AndyH]

Wow. Genius !!

I've got a couple of ancient Radio Control servos in the loft. I'll need to have a look at them and see if they open up.

Any links to places that sell pulleys, gears n belts etc?

Andy.

[nightfisher]

here is a couple of links for this project

Battery Free Electric Focuser

motionco_Plastic Gears_Spur Gears_1 Mod_Buy Stock Parts Online

very easy to do even i managed it, the mount is a skywatcher 100mm tube ring, but they dont fit tal tubes so i had to "enlarge" it with a drill and flap wheel, not a pretty job but works

[nightfisher]

I managed to try this system other night viewing jupiter, fantastic to focus and have zero image shake at the ep, definitely helps achieve better focus

[AndyH]

I'm going for a delve in the loft to retrieve the R/C servo's and give this a bash.

[nightfisher]

If you go ahead with this project and need any advice just shout

[Reggie]

Nice little mod Nightfisher I remember seeing these when I first looked at motors for focusing my SCT a few years back. It's worth noting that once you have modded your servo for continuous rotation, they now act like DC motors with speed control with their pot centre adjusted. This oipens up a few possibilities on top of the dynamo based focuser that you've built.

If you have any RC gear, the servo could be connected back to the RC circuit, as for instance the steering servo, your RC hand controller steering stick should now control the direction and speed of your focuser, pushing left will go one direction, right will take you the other way. You should be able to get speed adjustment by adjusting the stick anywhere from centre to hard left or hard right. hard left/right should give you the fastest speed.

If you don't have RC gear, you should be able to build a 'servo tester' using a 555 timer circuit, this will give you a wired alternative to RC controller kit.

[nightfisher]

thanks for the reply reggie, but i wanted to have the battery less system, so i have removed the potentimeters completely, rather than just centering them

[Reggie]

that's usually not an issue either, if you find out what the old pot is and wire a new one in it's place outside of the box to give speed control.

I thought I'd just share it with anyone that is messing with servos right now, I'm not for one moment suggesting that your current setup is 'wrong' in any way Just pointing out that there are other neat things you can do with a servo.

[AndyH]

Good info, Reggie !

Ta,

Andy.

[Reggie]

thank you