Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

heavy price to pay

Status
Not open for further replies.

dreamproject

New Member
hi all,

i had made the stupid decision to buy an LM629 ( for PID DC motor sevo control ) without thinking . Now I realize i need encoders to make it work (sigh !) . Does any one know where they r used (so i could rip off an old one without the price of a new one)

or atlest an idea of how much they cost . I will have to buy one frm the US of A because over here there r none made locally ( i'll have to check).


SOS SOS SOS SOS SOS SOS SOS SOS


thanks
 
dreamproject said:
hi all,

i had made the stupid decision to buy an LM629 ( for PID DC motor sevo control ) without thinking . Now I realize i need encoders to make it work (sigh !) . Does any one know where they r used (so i could rip off an old one without the price of a new one)

or atlest an idea of how much they cost . I will have to buy one frm the US of A because over here there r none made locally ( i'll have to check).

I'll say it for the third time! (I don't give up easily) - servo systems generally use a potentiometer as the feedback device!.

This gives accurate analogue positioning, and the pot provides permanent position indication. As soon as you power the system the pot tells it exactly where it is! - this is vital in a servo system! - particularly for steering a vehicle!. Most rotary encoders won't do this!.
 
Does your feedback element have to be a pulse-type encoder? How about using a multi-turn potentiometer instead. Using that, you get nearly infinite reolution, instead of discreet steps. Multi-turn pots are much cheaper than encoders too. I've seen that type of system used in industrial chart recorders for positioning before.
JB

*edit* Sorry, Nigel. We must have posted at about the same time! :)
 
I will ante up my 2 cents... All of the linear actuators ( think electric equivalent of a hydraulic cylinder ) I use have a 10-turn bourns pot in them. Some have a encoder wheel also, but this is for really fast or predetermined runs from one extreme to another. It is a very reliable, easy to implement ( one plastic worm gear and a spur gear ) and can be made to fit nearly any application.

Most importantly, as Nigel stated, it tells you what is where with out moving anything. This is a good thing, trust me. With only encoder wheels you have to "jog" the equipment from one end of travel to the other, then set a reference, do the math, and figure out where you were before you started moving things about. I have seen some equipment do this on start, but usually it is only done when other important info can be gathered at the same time. An example would be a plotter, it takes the head from one end to the other on start, since it will need to do this check to see what size of paper is loaded anyways.
 
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top