Technical, Techniques, Hints, and Tips => The "Black Arts!" ( Electrics & Electronics ) => Topic started by: markrider on April 30, 2016, 05:59:36 pm
Title: worm drive with limit switches
Post by: markrider on April 30, 2016, 05:59:36 pm
Hello I'm making a ferry with a bow door.I have made the worm drive and motor mechanism so that works fine. I'm just struggling to wire the circuit What I want to do is when you move a channel on the controller say down the servo with move a micro switch so turning the motor and lower the door. But I also want it to carry on untill it's down and the limit switch is reach this stopping it then push controller up to raises it etc. The circuit for the switchs on for servo and the limit switch is OK but the bit I'm struggling with is how to make it carry on after releasing the transmitter I think I need to make a layching really circuit but I didn't know how to do that. Hope that makes sense
Thanks very much
Title: Re: worm drive with limit switches
Post by: g6swj on April 30, 2016, 06:10:04 pm
Hi,
BarrrieW mayhem member recently did this - perhaps worth a PM
Check out post #71 http://www.modelboatmayhem.co.uk/forum/index.php/topic,53368.50.html
Jonathan
Title: Re: worm drive with limit switches
Post by: barriew on April 30, 2016, 06:26:40 pm
Mark,
I can't help you with the micro switches - I didn't use any. What I have done is use a microcontroller (Arduino) to move the servo to two set positions, depending on the position of the transmitter lever. Before I did that, I used an Action Servomorph which allowed me to set the end points and to slow the movement, BUT you still had to use the control to decide how far to move. Importantly, I used the non-centred control on the TX. I think that what you want to do - keep the servo moving even if the Tx control returns to the centre - may be possible using an Arduino, but would need to experiment.
Barrie
PS
If you look at http://www.modelboatmayhem.co.uk/forum/index.php/topic,40587.0.html - Bassplayer1 described the system you are looking for - can't remember if he gave a wiring diagram.
Title: Re: worm drive with limit switches
Post by: Plastic - RIP on April 30, 2016, 06:35:22 pm
The old way would be a couple of DPDT relays that use one contact to provide power to the coil so it self-latches and the destination microswitch breaks the circuit to disable the relay and enable the return relay - wired in a similar manner.
From a pulse input, it would travel to its destination and shut itself off. The next pulse would send it back to the start position.
There's simple circuits on google for this type of operation. Look at model train sites for simple end-to-end shunting tracks that do this.
Title: Re: worm drive with limit switches
Post by: markrider on April 30, 2016, 06:49:38 pm
Thanks for replys. Barrie has used the servo to move the ramp so can control the server via the arduino. But I'm runing it off a motor just using the servo to switch the switch to startvit moving. I have a look at the train forums
Thanks
Title: Re: worm drive with limit switches
Post by: Martin (Admin) on April 30, 2016, 06:59:52 pm
Title: Re: worm drive with limit switches
Post by: markrider on April 30, 2016, 10:43:49 pm
Thanks for you replys I think thy will help Assume the DPDT switch works like a latching relay ? All a great help thanks
Title: Re: worm drive with limit switches
Post by: barriew on May 01, 2016, 06:45:59 am
Mark,
Not as nice a diagram as Umi's, but this circuit uses micro switches rather than a DPDT switch. It doesn't latch. Push and hold the Tx stick one way until the limit switches stop the ramp. Release the Tx Stick and the ramp stays in place. Push and hold the Tx stick the opposite way and the ramp returns. I think if you want to be able to just flick the Tx stick, you need to add latching relays between the servo switches and the limit switches. Hope this helps. Good luck! Barrie
Title: Re: worm drive with limit switches
Post by: inertia on May 01, 2016, 08:35:19 am
It strikes me that most of these suggestions would do the job if you were to use a fifth channel, typically operated with a 2-way switch on the Tx. Having said that, it would then seem a bit strange to operate a servo to throw switches to operate another servo (in this case a motor plus worm-drive). You could just connect one servo direct to the door(s) and adopt Barrie's suggestion of a P96 to control the speed and throw. That's one of the jobs it was designed to do. DM
Title: Re: worm drive with limit switches
Post by: markrider on May 01, 2016, 09:25:37 am
Thanks people I did have a servo but it couldn't manage bring the door up even though it was high torque one so I made a worm drive and motor. It's quite a heavy door and pulling from the bottom so it's like the real ship as that has a hydrolic ram pulling from the bottom. So if I take barries diagram as that's how I figured it as well how would I put latching really in? I have a p96 but that won't work with a motor. I could get another transmitter with a switched channel but I want to use my transmitter
Thanks again
Title: Re: worm drive with limit switches
Post by: barriew on May 01, 2016, 12:09:39 pm
Mark,
The only thing my sketch doesn't give you is the latching. You would have to keep your finger on the transmitter stick until the ramp stops moving. I have never used latching relays so don't know anything about them.
Barrie
Title: Re: worm drive with limit switches
Post by: malcolmfrary on May 02, 2016, 08:13:16 am
The rather fetching blue drawing in reply #5 does most of the job. If the motor drives to one end, it has its circuit broken by the limit switch at that end. When the current is reversed by changing the state of the DPDT contacts at the bottom of the drawing, current passes through the diode allowing the motor to start driving. The process is repeated at the other end. The DPDT switch (or 2 microswitches or wipers on a PCB arranged appropriately) can be worked by a servo for momentary operation. The DPDT switch could just be replaced by the output from an ESC, but that would require that the operating signal be kept on until the motor has driven to its end point.
Title: Re: worm drive with limit switches
Post by: malcolmfrary on May 04, 2016, 08:13:30 am
The rather fetching blue drawing in reply #5 does most of the job. If the motor drives to one end, it has its circuit broken by the limit switch at that end. When the current is reversed by changing the state of the DPDT contacts at the bottom of the drawing, current passes through the diode allowing the motor to start driving. The process is repeated at the other end. The DPDT switch (or 2 microswitches or wipers on a PCB arranged appropriately) can be worked by a servo for momentary operation. The DPDT switch could just be replaced by the output from an ESC, but that would require that the operating signal be kept on until the motor has driven to its end point.
Re-posted because the automatic random text resize gnome struck the first line and I didn't notice.
Title: Re: worm drive with limit switches
Post by: Plastic - RIP on May 29, 2016, 03:37:09 pm
You could get the whole thing in one brick with a car central locking mechanism - limit switches, motor & worm drive in one box - just hook an ESC to the motor and drive it at whatever speed you like.
Title: Re: worm drive with limit switches
Post by: andyquirot on April 04, 2017, 09:00:56 pm
eBay item number:222455589122 These boards come with instructions on how to set a motor up with limit switches.
Title: Re: worm drive with limit switches
Post by: steamboatmodel on April 05, 2017, 06:06:43 pm
eBay item number:222455589122 These boards come with instructions on how to set a motor up with limit switches.
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