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OT: Possibly some help on electric linear actuator or similar design

viper

Titanium
Joined
May 18, 2007
Location
nowhereville
Here is another odd ball project. Father has a tractor mounted spreader that we want to convert to electric actuation to simplify his life. Force I need is not much (not measured yet) and stroke will only need to be an inch or so. I need something that works like a servo so the more voltage, to longer it gets or actually the shorter. Full on/full off will not work.

Can someone think of a product that might work for this? Basically this is just to open the dump feed window for the spreader. Very simple deal and I plan to install a pot to tune in the open position and a switch so once it is tuned, he just has to flip the switch and it feeds.

Most of the linear actuators I am finding are way too big and I still do not think they work like I require. Maybe a stepper motor or something?

I really want to stay with something linear acting to make the install simple. Torsional devices might require too much work to link up.
 
IN estimating performance, I will guess at no more than 5lb/ft of force.

Obstacles:

Must shut off feed at zero volts or some other type of return to shut off feed.

Must be somewhat dual acting to push the window open and pull it shut.

Will need to respond from full open to full close in 0-1.5seconds.

Really not wanting to get complicated in building a PWM control circuit for an RC type servo.
 
What you seem to be after is a proportional servo. If 10V = 100% open or out, 5v = 50 % open or out. As you are going to set it up anyway, why can't you adjust the "out" limit switch as required to open the flap and use the close limit switch to close the flap.
For a proper proportional system, the mechanical output is used to turn a potentiometer. This pot then returns a voltage proportional to the movement, this is compared to the voltage from the control pot. The difference between the voltages is amplified (a lot!) and used to drive the motor. For the limit switch type, no amplifiers are required, only the two limit switches and two diodes and the control switch, two pole change over with centre off.
For radio control models using digital proportional control, the two pots (users control and feedback) generate pulses of variable widths which are equal when the system is balanced. I doubt if you can get radio control servos with enough torque for your application.
Have you thought of using a bowden cable?
Frank
 
I do not need a feedback system for sure.

I agree that the off position could be an input voltage as well instead of 0VDC.

There a cable system on it now and the whole design sucks. Because this system is removable and the cable system does not work well, I am hoping to build a simple multi-pin plug for this app so he can just plug it in and flip a switch. I am sure I can find easier ways to do this so some of it is just for fun........I guess......

Where would I find a proportional servo used or ie, cheap? Nothing new and fancy needed here.
 








 
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