Electromagnetic solenoid actuators with 1" of stroke?

[fastline]

I am having a hell of a time sourcing a simple solenoid linear actuator with decent stroke. 18-25mm would be great but I really don't need much power. actually too much will just complicate the job. I would estimate 1kg of force max and I would still throttle back the voltage.

Anyone know where to get these REASONABLE? I mean I am sure there is a long list of people that will make what I need but this is a $5 part.

 

[KeepItSimpleStupid]

These are motors and not quite the stoke (0.75 inches, 19 mm) you want, but in the price range: **broken link removed**

Check here: http://www.ledex.com/linear-solenoi...parison.html?gclid=CLjUiejD_LICFVSd4AodxTEAhg I've used their rotary actuators and it's high quality stuff.

 

[fastline]

Oooh, I like that! We can possibly live with .75" of travel. Do you think these can handle continuous duty of the voltage is reduced? I am assuming they are not otherwise operated as such but also probably have a LOT more force than we need which is about 500g

 

[KeepItSimpleStupid]

I think I have a few of these at home. I would probably use current limiting if you needed a particular torque. They are cheap enough to try, so I would try a constant current source and monitor the temperature.

If you needed to reduce the temperature further, I'd use PWM. Jameco sells a Vellaman motor PWM controller that I have used for a solenoid, but I used the slow start feature to activate a solenoid a little slower.

Rotary solenoids are interesting gizmos, if you have ever used one. They HAVE to have the voltage reduced once they activate.

 

[fastline]

Well, I got this door popper. Neat little gadget. I determined that full power is WAY too much for my needs. However, what I need to do is provide constant power to it and I am curious about a few things from you experts.

1. I determined that somewhere around 6V and .100A or maybe even less is all I need. I need it to hold though and curious if a DC motor is guaranteed to fail in a situation like this? I realize this is mostly a heat based issue but I do not see how I could add a heat sink to this. I determined this device at full power will pull about 6-8A at 12V.

2. This brings us to throttling this motor down. How might someone here make a cheap and easy way to control both the current and voltage to the motor? Keeping the idea of 6V and .100A in mind.

 

[KeepItSimpleStupid]

I've used this https://www.electro-tech-online.com/custompdfs/2012/10/120539.pdf before. In terms of 6V and 0.1 A, that's <1 Watt. Your not going to have any problems there.

Other ides is to use a LM317T in a current limit configuration especially if a 6V power supply will work for you normally.

You can also look at various "solenoid drivers" https://www.lmgtfy.com/?q=solenoid+driver

 

[KeepItSimpleStupid]

These guys http://www.oesincorp.com/pickholdmodule.htm look like they know what their doing, but they look like their having a hard time presenting it.

In any event using PWM is a sound technology to use. What's kinda missing is a Bang A% PWM for x time, followed by a bang B% indefinitely with a logic input.
I think if you read "between the lines", the above is possible.

It is pricy. I could have used one like that 15 years ago. No biggie though, I had cooling available.

 

[KeepItSimpleStupid]

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[fastline]

Thanks for the reply. I have not checked the links yet but was also thinking of the LM317 which I use here anyway. I think the main question for now is, will PWM or more complex driving techniques have any advantage at all over direct DC power? IE, LM 317 operated with current limit. Both are adjustable. I will be using a micro controller anyway so I do have PWM output pins, no issue there. I just don't want to make a complex circuit if simple will do the same thing. In this instance I actually need to reduce the speed anyway so reducing the voltage is working much better so trying to get full power is just not needed.

I did run a gamble test on the actuator and at about 1W, and 15min on, there was slight warmth to the device but certainly not hot or anything run away. The issue though is this sucker needs to be able to stay on for 12hrs at a time. IE, any thermal gain is not good. Needs to stabilize and hold. Unfortunately, the way they make these, they are sealed so I cannot put a sensor on the motor to monitor temp very well. If I could see a break down, I could probably drill a small hole in the plastic for a TC.

 

[ronv]

The 317 would probably be the easiest, but will need a heat sink. Assuming you will change direction have you chosen a H-bridge to reverse it. If not we might be able to use it to current limit it to 0.1 amps.
2 ohms locked rotor seems pretty low for such a small motor, but could be. It will only need .2 volts across it to supply 100 ma.

You might consider just a 100 ohm 3 watt resistor.

 

[KeepItSimpleStupid]

I would control the pulse width on the peak current if you can measure it. i.e. A measurement taken 1/2 way through the PWM pulse. Since torque is directly proportional to current and torque is what you want to control that's the perfect way. So, you might need a computer controlled variable power supply as well.

If you need a better actuation profile you could change the power supply setting.

An adjustable current limit is yet another way to go.

 

[fastline]

I am not sure what a computer controlled PS is but I do have a lab PS with voltage and current limiting. That is how I am determining what I need. Maybe you are referring to more of a function genny where I could play more with wave forms to the device?

 

[KeepItSimpleStupid]

A power supply that can be controlled via USB, RS232, RS485, IEEE-488 or analog setpoints (e.g. 0-5V) 0-5 for voltage were common. In computer controlled mode, a 0-5 V signal would control the power supply output and another would control the current limit.

Then there were outputs proportional to current and voltage and sometimes logic outputs as to whether the supply is in voltage or current limit mode. Then usually a TTL crowbar signal that could be activated turning off the supply.

One of the reasons those supplies are expensive is that the voltage setpoint is relative to the plus terminal so,, isolation is sometimes optional.

Very common in lab supplies, but sometimes has to be ordered as an option and isolation is a sub-option.

Now it's common to find USB and RS232 controllable supplies.

Here: https://www.circuitspecialists.com/programmable-bench-power-supply-csi3645a.html They talk about USB and optional RS232, but the manual is very confusing. Isolation, if needed can be provided by B&B Electronics modules. Isolated USB can also be had with external adapters.
There is no mention as to whether the RS232 is isolated either.

Here is a model more like I'm used too. https://www.sorensen.com/products/DLM600/DLM600_Overview.htm This is another example of a programmable LAB supply that has lots of optional interfaces.