Which Arduino to use

I'm a complete beginner at electronics and code but am really interested to learn about it all. Right now I'm planning a simple project and could use some guidance.

Right now if any of you have suggestions for type of Arduino or other components and sources for them I'm happy to hear them.

Some of the specs:

  1. timer with tenth of second accuracy
  2. timer counts up or down
  3. timer can be programmed to trigger an external device at a time set by user via electrical signal
  4. after each trigger event, device automatically resets to await next start
  5. timer starts counting with single button push
  6. external device is a rod that moves in a straight line with a throw of about 2 inches, possibly solenoid or actuator?
  7. timer/trigger should fit into box no bigger than W 3" x H 2" x D 2"
  8. remote actuator or solenoid can be larger

Thanks!

OK how about this...which board should I use?

Or, if I haven't provided enough info, tell me what additional info I need to provide.

Uno is fine for your purposes. If the time is just supposed to do intervals, that's enough. If you care what time it is, you will likely need a real time clock (RTC) too.

Thanks Bill. No need to know actual time. Just need a timer that is easy to set and can handle the functions I mentioned.

So the Uno can also handle the triggering of an external device too? Because there's a mechanical component to that part of it I assume I'll need to control a a relay/SSR that can handle the larger load required to run an electro-mechanical device?

And if I'm posting in a forum that isn't really intended to answer questions like these can you guys direct me to one that's mmore appropriate?

Any Arduino can control a very large device by means of however large a cascade of transistors/relays you require.

It can, in itself, only provide 40mA at 5V but for a few pounds you can buy a relay or SSR that will switch several amps at 240V if needs be. Once you have a couple of KW at your command you can control nearly anything!

I have an arduino based device controlling a mains electric heater in my greenhouse. The relay board that it uses cost about £3 off ebay. It can switch 10A at 240V and any Arduino could provide enough power to drive it.

If space is an issue, you might consider a "nano" - essentially the same deal only smaller.

Cool. Thanks Dr Ugi.

Looks like the external device will be a car door lock actuator. It's 12 VDC at 25mA.

One more detail, this project is connected to a kitchen appliance and it would be nice to power everything by drawing from the 110 VAC supply to that appliance. Any advice on the most compact, simplest way to do that?

The Arduino is 5 V right? So do I need two different transformers to convert the 110 VAC to 5 VDC for Arduino and 12 VDC for the actuator?

2 transformers yes, and no you can just use 12 volt, and step it down to like 9v the arduino can take a wide range of voltages, but 12 is pushing it search fourum for "powerring the arduino from 12v like: http://arduino.cc/forum/index.php/topic,94247.0.html with something simple you can supply both. other option lookinto useing a servo to move your "bolt/pin" or what ever with the proper horn u should have no problem with 2 inches etc, and a servo can go 2 directions rather than one like the door acctuator. lots of servos are 5V with low power requirements and could be run directly off the arduino so only one power source!

Thanks for the input thebfs. That link contributed both to my knowledge and to my confusion. Lol

It sounds like since I’m using a mains power supply to the Arduino I don’t have to worry about how much of that power gets scrubbed off by the built in reg? I.e. don’t have to worry about battery life!`

I like the idea of using an actuator that runs off 5 VDC but I looked at some hobby and robot actuators and they seem to be either quite expensive ($90) or too small/wimpy to provide the throw/force I need.

So assuming I’ll be using the automotive actuator at least for this prototype, my understanding of how power supply will work:

  • I could step down and invert the mains 110 VAC to 12 VDC to provide juice for the Arduino AND for the actuator. I’m guessing a typical “wall wart” type supply would suffice?

  • One box will contain Arduino and SSR. Line carrying 12 VDC enters that box and is split, with one lead going to Arduino and other to SSR.

  • Arduino steps 12 VDC down to 5 VDC with internal regulator. Do I need to worry about heat building up here?

  • Actuator is contained in separate box and is powered by 12 VDC line running from SSR inside Arduino box.

  • Arduino controls SSR which controls power to remote actuator.

That about right?

That about right?

Not quite.

First SSRs (solid state relays) are used to switch line AC voltages not DC voltages (except for a few special SSRs) such that your actuator requires. You would need just a normal automotive 12vdc relay for that function, such as this one.

Second on sizing a 120VAC to 12vdc power supply/module. First you will need to know the maximum current draw of your actuator. Add another 1 amp or so for the arduino and the relay coil power and that will be the supply size you required.

Aha! Ok thanks Lefty!

So a simple relay to switch the actuator. And actually I'll still need a SSR to control the appliance that this thing is sitting on too.

As far as power supply then, the actuator is max 25 mA so with your recommended extra 1 A I need something that will provide 1.025 A. Lol Do you think 1 A would do it?

What's the best way to split that 12 VDC supply line?

So now I've got a box containing Arduino, timer display shield, SSR (to switch appliance) and relay (to switch actuator). What's the best way now to connect all this stuff inside the box? (told you I was a rank beginner!)

1 A should probably be ok especialy if you dont plan on switching both relays at the same time. to split the 12v buy a cheap 1 to 4 distribution box and mount everthing on a board, and use screw terminals or solder to put everything together, ot just solder up a Y on the line with some wire, and heatsrink the result.

a proto shield pcb for the uno would be good investment it will help hook everthing up

vanchopski: Aha! Ok thanks Lefty!

So a simple relay to switch the actuator. And actually I'll still need a SSR to control the appliance that this thing is sitting on too.

As far as power supply then, the actuator is max 25 mA so with your recommended extra 1 A I need something that will provide 1.025 A. Lol Do you think 1 A would do it?

The extra 1 amp is assuming you want to power the arduino board through it's external DC power connector. 25ma sounds awful low for a motor device, but if true then yes a 1 amp +12vdc power source should be fine.

What's the best way to split that 12 VDC supply line?

No easy plug and play. You can either splice into the cable so you have two take offs one to the arduino and one to the actuator. Another method is to just plug into the arduino external DC power connector with the supply and then wire seperately your 12vdc actuator from the arduino Vin pin and ground pin, which comes from the DC connector power.

So now I've got a box containing Arduino, timer display shield, SSR (to switch appliance) and relay (to switch actuator). What's the best way now to connect all this stuff inside the box?

Duct tape won't work well. ;) Basic wiring management methods I guess is the only answer I can fall back on, unless your more specific with pictures or requirements.

(told you I was a rank beginner!)

As we all were at one time or another. Lefty

@thebfs:

I just found a schematic for a power supply that was custom designed for the same appliance but the output is only 9VDC.

Component data:

Rather than using an external power supply it would sure be nice to run everything off the power supply to the appliance.

If a guy wanted to build a similar power supply but with 12 VDC and 1 A output how would he do that? Is it as easy as changing out that voltage regulator to one that allows 12 VDC?

not just the regulator the transformer may have to be changed to /other values moddified. sorry i dont haveany replacement part sugestions.

vanchopski:
7. timer/trigger should fit into box no bigger than W 3" x H 2" x D 2"

I’d be shocked if the Uno fits in a 2"x3" box, seeing as how it’s 2.1" wide. And longer than 3" (unless you cut a hole for the USB connector to poke out).

You’d be better served with something like a nano and a custom PCB to mount your components.

Just a thought.

Brad (KF7FER)

Brad,

Yeah I should have updated that spec. Lol

I've already got a box here that's a lot bigger. Big enough to hold Uno, LCD display, relay and SSR. It's bigger than I'd hoped but it'll do for this prototype.

If anyone can tell me which parts from that diagram could be changed to provide the 12 VDC @ 1 A that I need I'm all ears. That kind of figuring is definitely beyond my abilities.

Chops

Or maybe I'm posting that question in the wrong forum?

u could try general electronics fourum