Motor driven switch - Page 1
Forum section: electronics / beginners

author: FrankT
author_rank: Regular Contributor
timestamp: February 10, 2017, 01:27:41 am
content: I know you can get motor driven slide potentiometers, but I'm looking for a motor (or solendoid) driven toggle switch. I need to be able to manually turn it on, but then be turned off electronically (behind the panel - not like one of those useless machines)Are these available?I'm look to build a control panel for my CNC lathe, that simulates the operation of a manual lathe - Large wheels connected to encoders for the saddle traverse, a smaller one for the cross slide, and some large switches to engage the feed that will switch back to the off position once it has finished the pass.

author: Pack34
author_rank: Frequent Contributor
timestamp: February 10, 2017, 01:37:12 am
content: I would imagine this is just a DPDT switch wired to a battery and a motor.Common terminal on one of the sides would be wired to MOTOR+, the common on the other would be wired to MOTOR-. Then the remaining terminals would be wired to the positive and negative sides of the battery.To stop it when it retracts all the way you could just wire in a limit switch to break one of the positive battery wires.

author: FrankT
author_rank: Regular Contributor
timestamp: February 10, 2017, 02:45:28 am
content: After a bit more googling using different terms I found these at digikey...http://www.digikey.com.au/products/en?mpart=26ET1-T&v=480$1700 is a bit out of my price range though.I think I'm going to have to make my own.

author: Gregg
author_rank: Super Contributor
timestamp: February 10, 2017, 03:02:00 am
content: Try a search for:solenoid operated switchstepper switchstepping switchstepper relaystepping relayThe easy way may be to use a multi contact relay with one set of contacts used to latch the relay. That way you could have multiple stations with one momentary switch normally open to latch the relay and another normally closed that would unlatch the relay as the circuit was broken. A very common way to control motors

author: FrankT
author_rank: Regular Contributor
timestamp: February 10, 2017, 04:15:32 am
content: Thanks for all the replies, but it looks like I have not asked my question clearly.Latching and unlatching a switch is easy (I can use a relay for that).I'm more interested in the visible and physical feedback of the toggle lever...In picture on the left, the lever is in the off position. The spring return of the solenoid keeps the lever down.On the right, it is in the on position. This trips the microswitch, which enables the solenoid. The solenoid keeps the lever in the on position until either it is released by software, or the operator moves it back to the off position, releasing the microswitch which tells the software to release the solenoid.It looks like an affordable, off the shelf solution isn't available. (unlike those motor drive sliding pots).

author: Gregg
author_rank: Super Contributor
timestamp: February 10, 2017, 04:49:22 am
content: OK, I'm getting the picture now.Do a search for shunt trip breakers. When you turn these on they engage a catch that keeps them on against a spring but a small coil will pull off the catch and the spring turns it off. These are available in multiple pole configurations and in the larger ones the coils can be changed to different voltages but the smaller ones are fixed, Here is a US ebay listing for one:http://www.ebay.com/itm/Square-D-1P-20-A-Shunt-Trip-Breaker-QOB1201021-L-12-/360366595621They do make motorized circuit breakers that have a separate motor inside them to turn them on and off; these are commonly used on large 3 phase UPS systems to allow the system control to turn on and off the battery banks. Used they may be somewhat reasonably priced but you would have to source them for the voltage and frequency you need.

author: Zbig
author_rank: Frequent Contributor
timestamp: February 10, 2017, 01:09:24 pm
content: Does it have to be a lever switch? My dishwasher uses a pushbutton one that works and feels like the usual bistable latching one (i.e. push-in/push-out) but can be snapped back up (turned off/unlatched) electromechanically by the dishwasher itself at the end of the cycle. In other words: you push it in like a normal, mechanical one and it stays in, only to find it back in the off/up position (following the quite noticeable snapping noise) when you open the dishwasher after it finishes. Probably employs some kind of solenoid actuator.

author: Gregg
author_rank: Super Contributor
timestamp: February 12, 2017, 01:49:03 am
content: I had a chance to dig through mystoragejunk heap and found a shunt trip circuit breaker rated at 30 amps, 3 phase, 480 volts with a 24 VAC trip coil. It is a Heinemann Electric Co made in USA catalog # GB3-A2A3A-RV 24. It is about 150mm tall, 110mm wide, 110mm deep including the toggle lever.You may have it for the cost of shipping and whatever taxes/duties your country may charge. I tried the trip feature and it works very fast, it would probably work at around 12 VDC plus there is an SPDT auxiliary switch on the back that is meant to disconnect the trip coil as soon as it has tripped to not burn out the coil or drain your control circuit.PM me if you want it or want some pictures first.

author: FrankT
author_rank: Regular Contributor
timestamp: February 13, 2017, 07:41:44 am
content: Quote from: Gregg on February 12, 2017, 01:49:03 amThanks for the offer, but I've decided to try and build my own - it would probably end up in my storage heap anyway. I 3d printed a test model, and that seems to work ok - I'll machine the final version out of aluminium so it will survive in a harsh environment.

author: Ian.M
author_rank: Super Contributor
timestamp: February 13, 2017, 08:26:35 am
content: Another option would be to find a toggle switch that actually uses a slide switch mechanism, preferably one with open ends so you don't have to mod it, then add a solonoid or RC servo behind the panel to push the end of the slider when required.However, I think your idea of building your own is likely to result in a superior switch, with better look and feel, and if you use a sealed microswitch for the contacts, better reliability.Aluminium is prone to corroding and jamming if there is moisture + dirt around, so if you are using soluble cutting oil coolant or don't have a fully heated workshop, you should consider building it in steel and brass (or stainless steel and bronze for really harsh environments), avoiding steel on steel or brass on brass rubbing contact.