Control circuit to switch an time a 240 volts AC contactor

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Themightybear
Posts: 4
Joined: Tue May 27, 2014 11:31 am

Control circuit to switch an time a 240 volts AC contactor

Post by Themightybear » Tue May 27, 2014 12:20 pm

I'm looking for a extra low voltage control circuit diagram design.The electronic coil of the 240V AC contactor can be run on as little as 24 Volts AC or DC.
The contactor is in N/O status and controlling 32Amps switching a domestic stove via a numbered keypad which runs on milli volt/amp. I think the circuit will need a decoder and changeable coding devise for the the key pad. I don't know what I need else for the circuit, so I hope some one can assist me
I'm a licensed electrician but know very little about electronics. The project is to Demenia proof a domestic stove or any high voltage devise

bwooce
Posts: 21
Joined: Mon May 28, 2012 11:15 am

Re: Control circuit to switch an time a 240 volts AC contact

Post by bwooce » Wed May 28, 2014 5:09 am

Hey bear,

Sparkies are always welcome. An arduino can definitely do this for you, but can I restate what I think you're asking for?

You want to create a device that will have a numeric keypad. That keypad will in turn control a contactor to switch AC current to a device like an oven.

So some questions:
1. You're imagining a standard numeric keypad e.g. like a phone? Mounted on a box?
2. Battery powered?
3. How long should it power the contactor for when the correct code is entered? This could be an issue when combined with battery power, for example.

You may be able to use an existing keypad door control system, like this one, but I suspect you only want it to activate for a certain period of time? http://www.jaycar.com.au/productView.asp?ID=LA5355 I do seem to remember some of these things are programmable as they control door releases, but they might be in seconds and you'll want minutes or hours?

Sounds like a great and worthwhile project.

Regards,
Bruce

Themightybear
Posts: 4
Joined: Tue May 27, 2014 11:31 am

Re: Control circuit to switch an time a 240 volts AC contact

Post by Themightybear » Wed May 28, 2014 7:51 am

Hi Bruce,
To answer your questions and thank you for replying
Answer
1. yes, I have the little numeric key pad from Jay car, but the larger one looks better
2. No, I'm looking at an internal power supply. No battery supply
3. 15 minutes intervals unless the code is re-entered before the timer runs out or by pushing a by-pass button once the light comes on and before the 15 minutes is up.

As mentioned I'm also looking to install a small light on the enclosure that will come on at 14 minutes and go off at 15 minutes turning off the power to the stove also.
I'm using a higher amperage contactor because potentially the stove could be on for up to 2 hours or more. So the control circuit will need to be of high quality and durability to run for that length of time.
I did have a look at that link and I like the larger self contained key pad
Thank you again

bwooce
Posts: 21
Joined: Mon May 28, 2012 11:15 am

Re: Control circuit to switch an time a 240 volts AC contact

Post by bwooce » Thu May 29, 2014 1:50 am

Sounds great.

On the hardware front:

To keep it simple, you need an arduino of some kind (maybe an Eleven from Freetronics), your keypad, some LEDs, and a few other things. I'd suggest some pins to plug into the arduino sockets while you're getting this right too - you can solder it all together once you're happy.

The arduino digital pins will supply/sink 5VDC at a small number of milliamps, so you'll need a 5VDC-controlled low-mA relay(or MOSFET? there's a Freetronics-packaged one also in Jaycar) and then daisy-chain that to your contactor control pins. The supply voltage for the Eleven is 6-20VDC Max though (or regulated 5VDC) which is less than your contactor, so you'll need two ELV supply rails (or maybe a different contactor...can you find a 5V one?). I trust that you can work through that complication given your background.

On the software front, I gather you've not done any programming before? I, and others here, would be happy to help you with this given the application. It's not that hard once your get going, but there are a few design considerations:

1. There is an existing software library for matrix keypads. It uses quite a few of the arduino pins (7 or 8), but there should be plenty left over. So that's easy.
2. You want a re-programmable code? There is EEPROM storage (persistent) on the arduinos, I've not used it yet but that sounds fun. You might want to think about how to get into programming mode (a hardcoded master code?) and how to communicate success/failure of programming and/or activation (another LED again? a buzzer?)
3. The timer can be done internally with excellent accuracy for these short timeframes. You could make this programmable too if you're keen. Maybe this kind of thing, like alarm keypads: <master Pin>#<new PIN>*<time in minutes># And even the warning time could be done that way too, but one step at a time...
4. If you want to use something more than a small LED for the "about to turn off" indication then you might need more hardware. Those little LEDs are pretty bright now though (esp. blue ones), and it can be made to flash etc easily. The mA draw is the thing to keep an eye on - 40mA max per pin.
5. Anyone else want to comment/correct?

I'll gloss over the need for the enclosure that fits everything, another problem only you can solve to your satisfaction.

So what do you want to do next? You've got the Arduino software installed on your PC/Mac?

Themightybear
Posts: 4
Joined: Tue May 27, 2014 11:31 am

Re: Control circuit to switch an time a 240 volts AC contact

Post by Themightybear » Thu May 29, 2014 2:38 am

Hi Bruce,
Wow, I really appreciate the thought you've put into my project.
I read through all the advise you written Wow.
The closest to programming I've been was when I excelled in PLC's study at TAFE doing my Electrical trade in 1988. Even my teacher told me to continue the PLC study but work and family had higher needs. But I'll have a go at this and I'm more than willing to do any recommended reading and advise from the members of this group
What do I need next.
a circuit diagram
a wirering diagram
all programming advise needed
any methodology input
a parts list so I can order them from Jay Car at Rydalmere
I'm not sure if I have the Arduino software installed on my Mac yet, I will check that and install it if needed
Many thanks
Les (themightybear)

angusgr
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Re: Control circuit to switch an time a 240 volts AC contact

Post by angusgr » Thu May 29, 2014 11:15 pm

Themightybear wrote: I read through all the advise you written Wow.
The closest to programming I've been was when I excelled in PLC's study at TAFE doing my Electrical trade in 1988. Even my teacher told me to continue the PLC study but work and family had higher needs. But I'll have a go at this and I'm more than willing to do any recommended reading and advise from the members of this group
Hi Les,

You're more than welcome to keep getting advice here (and please keep sharing your progress, great project!) Another thing you could try is looking for a collaborator local to you in Sydney. The Sydney hackerspace is actually located very close to Rydalmere: http://robodino.org/

You could possibly ask for help in person there as well (sometimes having someone in the same room can save a lot of time over doing it online), or you could even explain the concept to them and see if anyone is interested in collaborating with you - it sounds like the sort of worthwhile project where you may be able to find someone to partner with. Hackerspace people often have use for qualified electricians so there may be some kind of barter exchange you could offer as well. :)

Look forward to hearing more about the project!

- Angus

bwooce
Posts: 21
Joined: Mon May 28, 2012 11:15 am

Re: Control circuit to switch an time a 240 volts AC contact

Post by bwooce » Fri May 30, 2014 3:44 am

Hey Les,

I'm sure you'll take to programming like a duck to water then. Before going too far with the physical plans, how about picking up an Eleven, and maybe some more LEDs and current limited resistors (or an Experimenters kit http://www.freetronics.com/collections/ ... or-arduino, sort of all in one) and working through some small examples. A small breadboard and solid-core jumpers wouldn't hurt. You can use a LED instead of the contactor while you're building the software so you'd not be wasting anything.

The Freetronics Eleven is an improved Arduino Uno, and you'll see the Uno in almost all the tutorials. It's a classic, but it's been improved on in Australia.

Start with an onboard LED tutorial https://learn.adafruit.com/adafruit-ard ... on-1-blink

and then progress to adding more on the pins (something like this):

http://www.instructables.com/id/Basic-A ... nking-LED/
The same kind of tutorials are also on YouTube if you want it as a video.

Nothing beats the thrill of controlling some lights via software for the first time.

Once you're confident doing that you'll have mastered editing the sketch (code), uploading to the board and the purpose of all the pins will become clearer. Then moving on to plug in the keypad http://playground.arduino.cc/Main/KeypadTutorial etc will be much easier, and I expect you'll be back here asking about programming timers and more hardware to control the contactor. I'm more of a software guy myself, so it would be good to get more help with that.

As Angus says, if you can find some help locally it would avoid/short-circuit some frustration and it is a great project that many people would be willing to help with.

Themightybear
Posts: 4
Joined: Tue May 27, 2014 11:31 am

Re: Control circuit to switch an time a 240 volts AC contact

Post by Themightybear » Tue Mar 17, 2015 9:39 am

Hi Bruce,
I did try the programming of the Arduino but got no where, but as yet I haven't time to get back to it.
I still want to make it work so any further advise.
I did search for a local club but unfortunately there's none close enough. I will however pursue this further. As you mentioned, I will need a circuit diagram. Could you please help me with that.
Thank you
Les

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