Reverse circuit

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24 July 2014 at 15:11 #50619
CookieOld
Participant
@cookieold
Hi All , Can anyone please give me a simple circuit that can change a motor direction using a limit switch at each end of a stroke , I want to use a motor to rotate a screwed shaft fixed to a platform that will move along and hit a limit swich sending the motor into reverse to send the platform back to hit another limit swich to repeat the process..

Thanks Cookie
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24 July 2014 at 15:11 #4128
CookieOld
Participant
@cookieold
24 July 2014 at 16:45 #50622
Dave Milbourn
Participant
@davemilbourn48782
I'm taking advice, Dave. Don't hold your breath, but……

Dave M
24 July 2014 at 19:36 #50630
CookieOld
Participant
@cookieold
Thanks Dave , I was hoping you would see this post.

Best Regards Dave
25 July 2014 at 09:40 #50646
Kimosubby Shipyards
Participant
@kimosubbyshipyards
Cookie,

I set one of these up on the Celestine ro-ro model.

My sincere apologises to Dave M for the use of a chocolate block, I have assumed the submissive posture and expect your reprimand, I have since changed my ways.

I used micro switches and a two way switcher from Electronize to cut the motor power when the travel had reached the required distance. This was a wormed shaft and the end point was not critical to the nearest millimetre.

This is the unit in position, and here's the wiring diagram (which I writ so it's not using correct symbols) but you should be able to follow the circuit through. Note there are no diodes, which I'm told ought to be installed to stop sparking and to ensure that the current flows only in the desired direction. My unit used a 3V motor, so voltage is stepped down from 6V, and after 4 years it still works.

The unit wiring is on the right of the diagram, labelled at its lower right corner as "ramp control". The switcher enables the motor direction to be reversed, by swapping the polarity.

Hope it gives you some ideas.

Kim.

Edited By Kimosubby Shipyards on 25/07/2014 09:40:48

Edited By Kimosubby Shipyards on 25/07/2014 09:42:55

Edited By Kimosubby Shipyards on 25/07/2014 09:43:35
25 July 2014 at 11:34 #50648
Dave Milbourn
Participant
@davemilbourn48782
Dave
Just to clarify matters; my understanding from your description is that you want this motor, once switched on, to continue running from one end to the other and then back again ad infinitum (or until it is switched off manually). There will be no radio-controlled starting and stopping at any point as in Kim's suggestion. I don't know what application you have in mind; it might help if you could explain that and also provide the value of the current drawn by the motor. I have in mind one of these gizmos with two microswitches **LINK** and a toggle switch to isolate the whole circuit from the battery.

Kim
Glad to hear you've said your Hail Mary's. We have certain standards to maintain, you know.
DM
25 July 2014 at 14:03 #50658
Telstar
Participant
@telstar
Hi Cookie I have, or can draw, a circuit that no matter where the screw platform is, when switching on of the isolator/battery switch, the motor will drive the platform to one end (always the same end). When the platform reaches that end and touches the microsw. the motor will reverse and run in the opposite direction until it touches the other microsw. when the cycle starts again ad. infinitum. It will use a 4 pole change over relay and 2off microsw. The motor volts need not be the same as control circuit voltage. No electronics involved.

Is this the kind of thing you need?

Cheers Tom

Dave Not trying to steal your Trade Tom

Edited By Telstar on 25/07/2014 14:05:34
25 July 2014 at 15:05 #50660
Dave Milbourn
Participant
@davemilbourn48782
Tom

I could have written it myself………….. almost! I'd be interested in seeing your solution.

Dave
25 July 2014 at 17:00 #50664
shipwright
Participant
@shipwright
Use a latching relay (eg Omron G2RK-2 DPDT) and 2 microswitches. The relay state is retained even though power is removed from the coil. There are variants but the G2RK has 2 coils – one for "set" and one for "reset". A momentary application of voltage to a coil (approx. 20 msec minimum) will set or reset the changeover contacts. I expect these relays are available from several suppliers but I know that they are available from Farnell at £6-60 each but note that they will impose a minimum order value (not sure but I think it is £25) and there will be a charge for postage and packing.

**LINK**/omron-electronic-components/g2rk25dc/relay-dpdt-3a-latching-5v/dp/2213735

Ian
25 July 2014 at 19:31 #50677
Dave Milbourn
Participant
@davemilbourn48782
Here's the circuit from me and Malcolm Frary, using the relay in my earlier link:
25 July 2014 at 20:31 #50682
shipwright
Participant
@shipwright
I should have waited for Dave's response ! I just carried out an experiment with a latching relay, small MFA motor and a couple of "push to make" switches (these because I don't have spare microswitches amongst my components). It works as expected. I actually used a very small latching relay (2 Amp rating) from Maplin :

**LINK**

**LINK**

If your motor exceeds 2 amps you will have to use a latching relay with a higher current rating.

Ian
26 July 2014 at 00:38 #50687
Telstar
Participant
@telstar
Hi Dave A rough sketch of circuit

M/s1 is n/c

M/s2 is n/o

Control voltage to suit coil on relay Diode is not essential

Relay pole’s all operate together

On switch on, relay is not energized. Motor will run towards M/s2 (if not reverse motor connections)

On reaching M/s2, the switch will operate energizing relay coil

Motor will now run the other way, relay pole1 will latch the coil energized .

On reaching M/s2, the switch will open deenergizing the relay reversing the motor once more

Possable relay **LINK**

Tom
26 July 2014 at 09:21 #50691
Dave Milbourn
Participant
@davemilbourn48782
Farnell's handling charge for orders less than £20 (excl VAT) is £3.95. Over that it's free delivery.
DM
26 July 2014 at 11:29 #50694
Malcolm Frary
Participant
@malcolmfrary95515
If anybody's wondering what the "extra" components are for, they are intended to act as spark quenchers to max out the life of the relay contacts, which will be switching a running motor. Even a small one (and we have no idea yet what motor is intended, or what it is actually going to do) can generate a fearsome amount of back-emf and do horrible things to relay contacts.
26 July 2014 at 12:12 #50696
Telstar
Participant
@telstar
Malcolm The resistor, capacitor circuit is as you say a switching transient damper (spark quencher) while the resistor in series with the motor is to try to reduce the 'starting surge' as the motor reverses

I agree that instantly reversing the motor will give problems especially if the motor current is near the max.relay contact current, but to build in 'time' for the motor to stop before reversing could get complicated.

Tom
26 July 2014 at 12:44 #50698
Malcolm Frary
Participant
@malcolmfrary95515
The problem with not knowing what the actual power requirements are gives a problem with shopping for parts. If power use is to be minimized, the polarized two coil relay is a clear winner since it only needs a brief pulse to change state, but only up to the limits of what its contacts can switch. The conventional relay with the self latching circuit probably uses a cheaper relay, but at the cost of spending half its duty cycle switched on and drawing current. Yer makes yer choice and yer pays yer money.
26 July 2014 at 13:29 #50700
Dave Milbourn
Participant
@davemilbourn48782
Cookie

I think we've gone as far as we can without knowing what motor you're going to use; what voltage, and what sort of current the motor draws. Until we have this information then anything else posted here will be just whimsy.

Dave M
26 July 2014 at 19:34 #50710
CookieOld
Participant
@cookieold
hi All, thanks for all the feed back sorry i should have been more precise about the application i intend to use this on . I want to use this as a means to lower the transom flap on my big Perkasa . I have designed all the mechanics and it works fine , I intended to use a MFA motor & gearbox with male & female threads to push the flap down and the fact it is a gearbox it will work as a brake to hold it when it is in the lowered position as the water will try and push it back up . When lowered i wanted the mechanism to hit a limit switch and kill the power to the motor so i could then move my remote stick the other way to reverse the flap back to level . I would love to put my CAD drawing on for you to see but i have not figured out to do it yet.

Cheers Lads Dave
26 July 2014 at 20:30 #50713
Dave Milbourn
Participant
@davemilbourn48782
See drawing "Limit Switches" – top diagram (P44). Your original description was quite a lot different from this one.

**LINK**

DM
27 July 2014 at 18:17 #50743
Kimosubby Shipyards
Participant
@kimosubbyshipyards
Ah,

can I now say my system does what the client requested – or should I go away? And its an MFA 3V geared motor! Glad you accepted my apology DM, I knew the sight of one would offend.

Not sure your link goes to correct page, "top diagram (P44)" limit switches.

Kimmo
27 July 2014 at 19:27 #50745
CookieOld
Participant
@cookieold
Hi Dave & Kimosubby , Thanks lads i know how to sort this now ,

PS . Sorry Dave if i have P***** you off with my lack of info in my first post.
27 July 2014 at 20:57 #50748
Dave Milbourn
Participant
@davemilbourn48782
Kim
The link will take you to a list of wiring diagrams. Scroll down to the one entitled "Limit Switches" and click on it. I have to admit that your solution was closer than mine (and Tom's and Malcolm's and Shipwright's), but that was because we were trying to do what was originally requested. I'll give you 4/10 for a good stab in the dark!
Dave M
28 July 2014 at 09:59 #50754
CookieOld
Participant
@cookieold
Hi Dave , Will the P44 be OK on 12V ,If so i will get one on order.

Thanks Dave
28 July 2014 at 15:57 #50760
Telstar
Participant
@telstar
Of course there is a non-electronics solution to this requirement. Using a standard servo to operate 2 micro switches to give Off neither switch pressed, Forwards micro switch ( 1) pressed and Reverse micro switch (2) pressed.

2 other mrcroswitches used as limit switches are used to stop the over travel ( by moving the servo to center at any time the carriage will stop where it is) The Diodes will allow the motor to be "backed off" the limit switch

All switches are shown in their normal ie not pressed position, and the diodes must be capable of carrying the motor current

Also the circuit is not voltage critical

Tom

Edited By Telstar on 28/07/2014 15:58:57
28 July 2014 at 17:52 #50761
Kimosubby Shipyards
Participant
@kimosubbyshipyards
Found it Dave,

I didn't look very hard did I… 4/10 thats about my average mark, just scraping a pass. More of a flash in the pan!

Kim (must get round to adding those diodes to the circuit, just looked and I have about 30 in the drawer, so must have been told before and got some.)
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