Reference article in January 2011 issue.
I thought that servos were powered by DC motors which overheat/burn out when stalled. Are servo motors actually stall motors? I like the design in this article.
Hi, Jim. Was your post, above, actually meant as a reply in another thread? If so, when you read my post, as you see it here, you can find a “Reply” clickable link that will open a text box and allow your message to appear in the same thread. Crandell
I was curious about this too. If you think about it, when you operate a servo normally, you try to push the servo, and it will push back and hold its position. The part that worries me is with the gear reduction, does the motor create too much torque? Possibly damaging the turnout?
Since this is being done, it is OK. Read the article again.
Do a Google search for this. I did and found plenty of articles on using servos for turnouts.
Rich
Count me as a naysayer. I do not believe using a servo as a stall motor in the long term will work. It does depend on the servo you use like that - the small ones I use are coreless motor sand would NEVER stand to be stalled continuously like a Tortoise.
Too much torque, I do not see being a problem. Unless you use servos meant for 1/4 scale aircraft or a sailboat sail winch servo.
Yes, servos push back when you push against them - but when they find their position the power to the motor is cut off. They do NOT stall. In an RC model application, if the servo can;t reach position, you need to use a higher torque servo so it can, you can;t just leave it stall.
I DO use servos to operate my turnouts, but NOT like the article. I use controllers from Tam Valley to operate the servo as intended.
–Randy
having not yet received the january edition so i’m flying blind, i would suggest some springyness is worked into any linkage ( like the tortoise wire rod ) so if the servo over drives slightly it can be allowed for. another point is that unlike the tortoise, most servo drivers,( and actually some digital servo’s have the option to programme onboard with a programmer, check out HITEC ) have the abillity to set the travel. so it can be told where to stop moving rather than finish it’s full travel.
The actual servo controllers, like Tam Valley, Team Digital, etc. DO set endpoints. The Tam Valley Singlet I use actually finds those endpoints automatically. The method in the article actually removes the controller board from inside the servo and just hooks two wires to the motor to run it like a Tortoise stall motor - no electronics.
–Randy
Since you can control servos using Tam Valley Depots products for $4 a servo, is it really worth it to go through the trouble of disassembling them and the risk of burning up the motor by using it in a way that it was not designed to be used? For some, maybe, but not for me.
I have to agree with CSX Robert on this.
Although there is a lot to be said for rolling your own, when you consider that a Tam Valley servo/decoder board/mount kit is $20 I’d rather use my kit bashing skills in a different arena.
Making an electrostatic grass applicator from a $3 Harbor Freight electronic flyswatter comes to mind…
Well, the Tam Valley decoder kit cost about $12.
The MR servo mod is mostly labor and a couple of resistors. The trick is to keep the current through the motor armature low enough so it doesn’t burn out when the motor is stalled, and at the same time allow for enough current to make sure the motor turns when not stalled.
For a $4 servo, it may be worth experimenting with.