Limit switch wiring help

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Hotpoker

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Hi All

Yes! I have another one of those automatic coop door questions! Sorry I could not find the right answer for my application.

Here is what I have got:
Automotive electric window regulator
DTDP time delay relay with the following pin configuration:
13 = - coil terminal
14= + coil terminal
9 & 12 = COM
5 & 8 = NO
1 & 4 = NC

Photo Switch
NC limit switches x2
DPDT switch to enable bypass of the relay


I have the wiring figured out to reverse the polarity using manual DPDT switch, and using the DPDT relay and photoswitch. This all works perfectly with the window regulator operating as intended - up and down.

What I am struggling to figure out is:
1.) How to wiring the limit switches into stop the regulator at the correct point; and
2.) How / where to connect the DPDT switch to the circuit with the relay, limit switch and photo switch.

A wiring diagram or sketch would be helpful!

Thnaks
 
Hotpoker said:
A wiring diagram or sketch would be helpful!
Click to expand...

yes, that would be very helpful, you first. It would be hard for us to tell you where to put your limit switch without first knowing how your circuit is wired.

But, as a helpful suggestion, the 'up' limit switch should only affect the 'up' part of the circuit. The 'dn' function still has to work with the 'up' switch opened, and vice versa on the 'dn' side.

It would also depend on how your motor is wired. If it has 3 wires, a common, an up input and a down input, then the 'up' switch would go in the up input, and the 'dn' switch would go in the down input.

If you reverse the polarity to the motor (two inputs) for up/down, then the switches would be in series on either input wire, and you'd need a diode across each switch (different directions) to allow current to flow in the opposite direction when that particular switch is opened.
 
Use of a single non-latching relay implies that the relay coil would (depending on your proposed circuit) have to stay energised during either the 'door open' or 'door closed' phase, otherwise the motor would move the door to the opposite position. This would waste power (and rapidly discharge any battery used as a power source).
 
What does the photoswitch do?
Current draw of motor? It CAN help?

For a SIMPLE system picture using diodes, so that the limit switch only allows the other direction? But, this design CAN require the limit switch and the diodes to handle full current. e.g. Make the limt switch open at each extreme and place a diode across the open switch, so the motor can ONLY go the other way.

There are TWO ways to handle direction and enable. One is to actually use a FWD signal and a REV signal. The other is to use a NOT ENABLE and a DIRECTION SIGNAL.

Using NOT ENABLE means that the motor won;t move when stationary.

It would seem that you would want the photocell to start stop the system and the limit switches to enable/disable a direction. So, it gets a little more complicated.

Think the same way, enable/disable a direction with a diode and limit switch, but use a relay to switch the motor power.

The photocell controls the power.

Doing this without wasting power is a challenge.
 
Guys,

Thanks for the help.

Yes, the photoswitch controls with the DTDP relay direction of the motor / polarity / up / down motion

The diode over the open switch limit sounds like the solution I am looking for.

As for wasting power - this is something I am concerned with. The 12v power supply is a 110w AC garden lighting unit, wired with a DC rectifier. In order not to waste electricity - I guess some form of timer would be required to energize the circuit for 10 seconds or so that it requires to operate?

Thanks
 
Do you really need a timer if you are going to use limit switches plus the photoswitch to determine whether the door should open or close? The scenario I envisage is:
At dawn, photoswitch turns on.
Motor runs in 'door raise' mode.
Top limit switch operates when door is open.
Motor stops.
At dusk, photoswitch turns off.
Motor runs in 'door lower' mode.
Bottom limit switch operates when door is closed.
Motor stops.
 
Last edited:
Yea, and my brain being as wierd a it is says photoswitch tops door when chicken is in the opening.

At least you understand the limit concept. It works nicely when there is an OPEN/CLOSE non-relay switch.
Yes, you could conserve power by pulsing a magnetic latching relay or probably making the pulses longer than ot takes to open/close. Maybe.

Aside:
Hey alec, time to do a blog post on limit stuff. It's come up enough.

I still like th contoller that does:
tap - reverse direction if stopped
tap tap - stop and reverse direction
tap when running = stop

Plus some edge triggered and binary inputs.
 
Alec - correct.

Although during the intervening hours the 12v transformer will still be consuming power.

To reduce power consumption what i am thinking is a 240v photoswitch (instead of the current 12v) coupled with a SPST interval time relay that can energise the transformer / circuit for a few seconds, long enough to run one movement (up/down).

BTW - picked up the diodes this morning - and will give it a crack tonight.
 
You could work on the power consumption later. If you mean "Fantom power", that's a different issue than having to keep a relay engaged all of the time under battery power.

You can always invest in a switching power supply that provides the 1-2 W standby power

Really conserving power may require a microprocessor base solution with the processor able to enter deep sleep.

You can dispense with the photocell and go with an astronomical timer. e.f. X <time> before or after calculated sunset.
 
Although during the intervening hours the 12v transformer will still be consuming power.
Click to expand...
We can design a circuit so that the transformer standby secondary current is only a mA or so. Standby power would then be negligible. Your DPDT relay coil would be the major current consumer if left on, but we can avoid that.
You can dispense with the photocell and go with an astronomical timer
Click to expand...
.....probably at an astronomical price

@KISS
Hmm. I'll have a think about the blog (or an article). Or you could do one? The 'reversible motor plus limit switches' concept has certainly cropped up under various guises apart from coop doors.
If the door is raised and lowered by a cord then the hen should be safe without the extra photosensor. Kind thought though.
 
Well, do it the wierd way. Take an astromonical timer and connect to a UPS and then the chicken door. It gets the job done.

I use an astronamical timer for one interior light. Timekeeping is kept runnimg with a 3 tiny LR44 batteries.

There was an article in Nuts and Volts about a building lighting systme with backup.

The timers are hard to find.
 
The photoswitch is light operated - turning on at dusk and off at dawn - nothing to do with sensing the chickens proximity. The dpdt relay has time delay fully reducing the chance of a chopped chicken.

So how do you design / wire the standby wire circuit?
 
"Thinking out loud"

One way might be to turn the limits into edges and activate a magnetic latching relay or low power flip flop or using LED/FET based relays.
Let's see what alec comes up with.

Any luck getting the diode limits to work?

Light always has problems with clouds and rain and false triggering.

You can always do it with a mini PLC: http://www.attf.info/a9004.htm

Here is the same company again, http://electrodepot.com/migroplc.htm but no real info on features.

My timer was about $15 off of ebay because the original one I had broke. It just plugged into the wall outlet. You need nomething better.

Not sure if this http://us.idec.com/Catalog/ProductSeries.aspx?SeriesName=IDEC_SmartRelay&FamilyName has the astronomical feature, but I played with the programming demo at one time and it was easy.
 
Last edited:
This would be my approach :-

The light sensor is a simple photo-resistor and should be protected from rain/dust to avoid problems KISS pointed out.
The relay would need a 12V coil and contacts rated for DC switching of an inductive load at > max current of the wiper motor, although in this design power is actually switched by MOSFET M2 rather than the relay contacts.
Standby current (motor off) is only ~ 0.5mA.
Push buttons enable manual over-ride for up and down.

@KISS
You did well to get an astro timer for $15. The ones that showed up in a google search were anything up to ~$300 !
 

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Alec - thanks for the wiring diagram.

Will give the diodes a bash first then worry about the power consumption - like the idea of the MOSFET.
 
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