Electric components to toggle DC motor polarity

[spec]

Here is an MCU version of the coop door controller:

Issue 33 of 2016_07_23

ERRATA
(1) 'COUP' should read 'COOP' in all instances

NOTES
(1) This is an outline functional block diagram of an Arduino Uno microprocessor unit (MCU) based coop door controller, as previously mentioned.
(2) This is an absolute system where the door opening and closing commands are absolute and not sequential
(3) The two shields (input output modules) just plug into the Arduino board and the two motor wires just fit into a terminal block on the bridge shield. No soldering is required.
(4) Including post and packing, the total cost is, £5.29UK:
(4.1) Arduino MCU: £3.00UK. **broken link removed**
(4.2) Real time clock (RTC) shield: £0.99UK**broken link removed**
(4.3) Motor driver twin bridge shield (L298 chip): £1.30UK. **broken link removed**
(5) Writing a sketch (program) to execute this task would be straightforward and simple.
(6) The Arduino sketch is written on a PC using the free Arduino Integrated Development Environment (IDE) and 'Processing' language. Python, C, or C++ languages could also be used.
(7) Door opening and closing times would be set with a PC or mobile phone (with appropriate application).
(8) Coup door opening and closing times can be set to any reasonable complexity, including automatically accounting for varying daylight time.
(9) Communication between the Arduino and PC/mobile phone for sketch loading and time setting is via a USB cable.
(10) Motor power dissipation can be limited by software timing if necessary and, in the extreme, the ST L298 chip on the bridge shield has motor current monitoring. https://www.st.com/content/st_com/en/products/motor-drivers/brushed-dc-motor-drivers/l298.html
(11) Apart from the motor, there are no moving parts to wear out.
(12) The RTC is battery backed so that the loss of 12V power will not corrupt the time.
(13) As the system is absolute, the temporary loss of 12V or door movement prevention, for any reason, will not put the door opening and closing sequence out of kilter.
(14) Note that the bridge shield already has four catching diodes incorporated for each of the two bridges (one bridge not used).

 

[ChrisP58]

What initiates the signal for door open and close? Could it make two different signals? One for each direction?

 

[KeepItSimpleStupid]

RTC or real Time Clock

Reality would suggest computing sunrise and sunset and do times relative to those.

 

[spec]

What initiates the signal for door open and close? Could it make two different signals? One for each direction?

If you are asking about the block diagram in post #61, yes there are effectively two separate signals. The two lower lines from the Arduino to the motor bridge shield are 'ENABLE' and 'DIRECTION' (the block diagram has been updated to label these two lines), so that you can command:
(1) Motor off
(2) Motor on clockwise
(3) Motor on anticlockwise

spec

 

[spec]

RTC or real Time Clock

Reality would suggest computing sunrise and sunset and do times relative to those.

Yeah, you could have a light sensor shield (another £0.99UK) to detect the onset of dusk and dawn.

When we had chickens it was always a worry that Mr Fox would get them.

The chickens would start getting anxious about an hour before dusk so we made sure that they were securely in bed by then.

About an hour or two after dawn they would be waiting to be let loose again.

spec

 

[Tony Stewart]

This is how I would do it.
<2A limit microswitches for open and closed to disable relay for Up and Down respectively
The timer controls On and Of which corresponds to Up and Down while the limit switches turn off the motor only in to direction to prevent the motor from stalling, but not prevent the reverse.

To implement this <$20 requires two limit switches with buttons or levers on buttons (spst) between V+ and two Relays incorporated in a winch reversal solenoid Contactor **broken link removed** rated for 150Ap.. This is the motor reversing DPDT with V+ 12V inputs separate for Up& Down

A second relay controls the direction {to signal} powered by your timer contact closure to 12V with common V-

I hope someone can redraw better using actual parts

 

[KeepItSimpleStupid]

Chris:

Here's https://www.maximintegrated.com/en/products/power/switching-regulators/MAX20082.html a more comprehensive motor driver which you can really take a look at. The reference design that i posted for an automotive system is also worth looking at.

Simple motor stuff is a project I did back in the 80's. If I was doing the project today, I'm not sure I would even know where to start. Even though there may have been enough power to do what i had to do, I took an approach that I could get to work. It was a Gantry crane for a model railroad. A farmer asked me to "automate this" without any co-oberation. He also changes things with design #2. Many things got better, but a few got slightly worse.

I also share the desire to automate a curtain as Les did. I chose the limit switch method and I had access to a machine shop.

 

[spec]

Chris:

Here's https://www.maximintegrated.com/en/products/power/switching-regulators/MAX20082.html a more comprehensive motor driver which you can really take a look at. The reference design that i posted for an automotive system is also worth looking at.

Simple motor stuff is a project I did back in the 80's. If I was doing the project today, I'm not sure I would even know where to start. Even though there may have been enough power to do what i had to do, I took an approach that I could get to work. It was a Gantry crane for a model railroad. A farmer asked me to "automate this" without any co-oberation. He also changes things with design #2. Many things got better, but a few got slightly worse.

I also share the desire to automate a curtain as Les did. I chose the limit switch method and I had access to a machine shop.

Hy Keep,

Thx for the information.

That Maxim chip, MAX20082, is quite something, but unfortunately it has now gone obsolete.

I think that the L298 based shield that I listed in post #61 is ideal for this application: good parameters, easy to use, off-the-shelf, and unbelievably cheap.

When I first heard about Les' curtain controller, I was greatly impressed.

With an MCU approach you could have remotely controlled opening and closing, light detected opening and closing and any thing you like.

Perhaps we could start a new thread about curtain control.

spec

 

[alec_t]

..... and here's my offering. This avoids the need for relays, involves only small currents through NC limit switches and manual over-ride push-buttons, and has virtually zero standby current (i.e when the motor isn't actually running). Should be doable for <$10.

 

[dcwatson84]

So in terms of limit switches - It needs to be something that the door can place pressure on when it reaches the top. But it also needs to be automatically released when the door goes back down. Are there spring loaded switches that can I use for this?

Edit - Momentary Spring Return looks like the way to go for these limits.

 

[alec_t]

Are there spring loaded switches that can I use for this?

Microswitches. Salvagable from many household appliances. They usually have NC and NO contacts and weather-resistant types are available.

 

[MaxHeadRoom78]

You are better off to get shrouded or enclosed L.S.'s for outside use, search ebay for Honeywell, they also come in hermetically sealed versions.
Max.

 

[atferrari]

What initiates the signal for door open and close? Could it make two different signals? One for each direction?

RTC or real Time Clock. Reality would suggest computing sunrise and sunset and do times relative to those.

Simpler: train him to push the button after crowing. Additional option, yelling "In two minutes, everybody out!!"

 

[atferrari]

Rooster aside. I came late to this thread.

I recall solving the problem of continuous drain of batteries to keep a relay in a certain condition by reversing the logic used with the contacts. The drain was then just occasional to create a brief temporary condition. I forgot the details. Isn't it an option here?

 

[Tony Stewart]

..... and here's my offering. This avoids the need for relays, involves only small currents through NC limit switches and manual over-ride push-buttons, and has virtually zero standby current (i.e when the motor isn't actually running). Should be doable for <$10.
View attachment 100560

ok design, only corrosion issue is the limit switches need e-caps across contacts to discharge to burn off oxide.
and glitch filter on input.
appliance contacts need 10% min.of rated current as contact wetting current

I like the idea of rooster α activated switch and/or solar θ switch.

 

[alec_t]

the limit switches need e-caps across contacts to discharge to burn off oxide.

Good idea.

glitch filter on input

Yes, if timer output is a mechanical contact; but probably not needed if timer output is solid state. The TS hasn't posted the timer spec.

 

[dcwatson84]

I appreciate all the designs! Ive tried to take as much from them as possible, but im new to circuit diagrams so I still sometimes have questions. I'm going to give it a shot at creating one myself with minimal parts, but before I post something really stupid I do have a quick question...

1. I'm thinking of using latching-relays (stay-relay?) in a couple places so that the system can be completely powered off when the motor isn't running. Is this reasonable?
2. In my draft diagram I have a couple places where the throwing of a switch needs to perform multiple actions. I have no doubt that that is possible - however one of the actions is actually un-latching the power going through the switch itself. So I basically want the switch to trigger some relays momentarily and also cut its own power via a latching relay upstream. It sort of implies that all these things need to happen simultaneously. Is that sort of thing a bad practice? Or prone to failure?

If Im not describing this correctly I can try to draw it out...

 

[Tony Stewart]

limit switches cut the power in one direction only.
what is overall requirement for control? input , controls, output?....

 

[dcwatson84]

Ah, good point - I guess what Im saying is that the limit switch is being used to apply current, not to cut it. This current is then being used to alter the state of other latches in the system. Maybe that completely defeats the purpose of limit switches, since they are designed to act quickly when a limit is reached?

I guess I should redesign my system with that in mind? I understand how I could use that switch to kill the motor, but I also need to use that switch to alter the state of the system at the same time, because it's acting as the reversal signal.

Should I scrap the "limit" switch, and use a "momentary" switch? Which I think can be used like a normal switch, to apply current when the door pressed against it?

 

[Tony Stewart]

maybe you should redefine required inputs & responses and stop thinking about how to implement.