electronic timer project help needed

[huntmaster]

Not sure how to get to where I'm going.

I need a custom electronic timer, and I'd like to build it, but I don't have the knowledge.

Here's what I need: Timer to buz twice at start and start several part count down, all programable. X seconds go buy, it buzzes one more time. A couple minutes go buy, it buzzes two more times. Thirty seconds before the last buzzer goes off, a yellow light on the clock cabinets turns on.

The process needs to be interuptable with a buzz. Also, I'd like to make it with 7 segments.

Anyone have an idea of how to build this unit? I'm in a real pinch here and need to build it. Nothing is available for timing our event, so something has to get done.

 

[(*steve*)]

Depending on your experience, I'd say a picaxe would be the easiest way to go.

If you've got no programming experience then it will be a steeper learning curve, but at least you can keep reprogramming it until you get it right

I'm not sure if you mean that you want 7 channels, or if you want a 7 segment LED display.

For the former, it may be easier (unless you understand multiplexing) to make 7 individual units.

For the latter, it's not hard to interface to a 7 segment display. If you start with a unit that has plenty of IO capability it would be easiest as you can dedicate inputs and outputs to the various lights buzzers and switches you require.

It would be *slightly* cheaper to use a plain PIC, but unless you're familiar with programming them, *AND* have a programmer it will be harder and more expensive overall.

 

[huntmaster]

I'm looking for using a seven segment light setup - probably 3 digits.

As for how the unit will lay out, I need a controll box, then the two "clocks" to be out about 60 feet or so in front of me.

I don't have any experience with this. I've done tons of things new to me, and I think this would be a blast to make. Only problem is that I don't know where to get the knowledge, nor where to start. That's why I am posting here. Can someone help me get started?

 

[(*steve*)]

Do you want 7 segment displays located 60 feet from you and still be readable? And I presume in daylight?

Do you have any programming experience at all?

Google "Picaxe" and follow the links to get you some idea of what this chip can do.

 

[huntmaster]

The only programing experience I have was years ago. Went through several years of computer programing in verious languages, but it was not in the current languages - ie pascal, basic, logo, and just a bit in fortran.

Yes, several yards in front and readable, but with 10" 7 segments behind red plexiglass it should be possible. That is the way many are built.

I found the picaxe information, and how to purchase. Can this run my timing system?

 

[(*steve*)]

OK, BASIC is good -- PICAxe chips use a form of that. They're very easy to program.

I would suggest that you first make something that works with small LED displays that you can breadboard and debug before you progress to large and expensive displays.

I'd be interested in what 7 segment displays you intend to use. (I guess you mean something like this: http://cgi.ebay.com/4pc-10-inch-ver...emQQptZLH_DefaultDomain_0?hash=item3a54d8b203 )

There will likely be an issue with driving these things over a distance, you may want to research the displays and find out their drive requirements, and whether they have any built in intelligence. If like the above then clearly they're not going to be driven directly from the PIC output pins, so you'll need some sort of driver circuit.

I'm not sure how accurate a PICAxe program would be. Certainly it would be precise, but you may have to tweak it to get accuracy too. This would be a question I would ask at some dedicated PICAxe forum. I'd probably go for the largest PICAxe because it gives you the most I/O pins.

You're going to have to research how people drive multiplexed 7 segment displays and simultaneously do accurate timing and (presumably) scan for switch activations.

I would advise you to tackle the problem in parts. Start by understanding the problem well (possibly expressing it as a state machine) then learn to handle the PICAxe and drive the display. Then learn how the timer works and add that so your program can count down. Then add other control logic to handle resetting the timer etc. Trying to do it all at once is a recipe for disaster unless you're very experienced (mostly because of the interesting issues to do with interfacing to hardware).

 

[huntmaster]

Actually, those are exactly the ones I'm looking at. I know I can get a chip to run the displays, but don't have any idea how to get the main board to run the displays.

I'll start by getting the info on the picaxe and maybe getting one purchased. Can this be set up to run a simple "stop light" type signal as easily? I can do that and run switches to get the times I need. Green for go, yellow for warning, and red for stop. it might be an easier way to get this started.

Bassically this has to be up and running in a month. I need at least something then.

 

[huntmaster]

Perhaps it's a project I can work on for a bit longer later.

I have something that I may be able to do. I've got an old garage opener remote and reciever. The reciever just sends a signal for the garage door to start. Hook it up to start a timer that runs a pair of stop lights powered by 120v. That way all I need for now would be a sound signal when started and turn on a green light, X time later, switch to the yellow light, Y time later, change to red light and sound again. I could use dip switches to set the times even. Most of the time, X will be 90 seconds, Y will be 30 seconds, but X does change sometimes.

Later I could redo it to run LED's.

Perhaps this is a little more along my learning curve.

 

[(*steve*)]

That should be possible. I'd suggest you get one of the kits they sell with a prototyping board and stuff. That way you've got all you need to start breadboarding a solution. Some of these have LEDs etc built in, so you can do all your software development and then design/build the hardware as required.

Possibly start with an AXE091 development board ( http://www.rev-ed.co.uk/docs/axe091.pdf ) plus programming cable and 40 pin picaxe. It's one of the more expensive ways to start, but it will be faster than "rolling your own".

And as you suggest, start with simpler versions of what you want to do and build up if time permits.

Here's a method of getting accurate interrupts on a PicAxe. You could use it to control the timing of the multiplexing of your display as well as incrementing/decrementing your timer display. For example, if you set it for 100 interrupts per second, you could on each interrupt:

a) display the next digit on your display (so it gets scanned 33 times per second)
b) increment a counter -- when it reaches 100, a second has passed, so reset to 0 and change your countdown timer.

The "normal" program could be scanning keys to determine if any are pressed and setting states to control the activity of the timer.

 

[(*steve*)]

Perhaps this is a little more along my learning curve.

How much experience do you have working with mains powered equipment? Some mistakes can result in a nasty case of death (for you or someone else) so I'd be very careful.

I would advise you to make a low voltage circuit that drives relays and use the relays to switch higher voltage equipment. Better yet, try to find lights that run from a lower voltage (if outdoor, running from a 12V car battery may be more convenient anyway).

For a serial timing task like this I'd still be inclined to use a PIC. For this new task though, the programming is simpler, in brief:

1 - turn off everything, turn on "red" output
2 - hang around waiting for some "start" input (from the receiver)
3 - turn off everything, turn on "green" output and "sound output"
4 - wait for 2 seconds
5 - turn off "sound" output
6 - wait for 88 seconds
7 - turn off everything and turn on "yellow"
8 - wait for 30 seconds
9 - turn off everything, Turn one "red", turn on "sound"
10 - wait for 2 seconds
11 - go to 1

This could very easily be a first step in getting to the deluxe model you want.

If you get this working, you may even want to allow for a second press of the button to take you immediately to step 9

You could do this in one of the picaxe-08 chips which are very cheap. You have 5 I/O pins, one for red, green, yellow, sound, and receiver. These chips, along with a resistor, transistor, relay and a diode for each channel can switch the higher powered loads you want. Note that the PICAxe runs off 4.5 to 5.5 volts, so you'll either need to run it from a separate low power supply or have a 5 volt regulator to supply the required voltage.

 

[huntmaster]

Sounds like it's a project then. I've got the controller on order already (probably not the best price, but beggers can't be choosers LOL )

I'm shopping for a new multi meter since mine is bad tomarrow.

I did a little looking for a relay switch, and only came up with auto or industrial stuff.

Looks like I need a power supply too. I see I can get a laptop charger that has 19v output, and I dug into the reciever for the garage door opener, and it has a 24v output. I'll probably need a converter for it too right?

I've also seen a 12v converter used for 12v home use.....would one of those be better?

 

[(*steve*)]

you need +5V for the picaxe. Many cellphone chargers are 5V -- have a look at some old ones you might have lying around, they may be what you need for the picaxe. If you need to use a higher voltage powersupply, you'll need a regulator. Look up 78L05 (there are plenty of threads on this site that mention it) and use one of those. If you can't find anything, use 3 AA cells (approx 4.5V).

Note that you need a programming cable for the picaxe and the software (the software is free). Beginners often stuff up the programming connections which is why I recommend a kit that has this stuff already in it or available with it.

Just start by using LEDs to indicate the operation of the circuit and move to relays (or some other high current driver) later.

For a start, use a push-button momentary contact switch for the receiver input.

After you get the basic code working, figure out how to interface the receiver.

 

[huntmaster]

Well, I got the Picaxe 08 proto board in. I'm soldering it up in a day or so. It comes with a 9v batery hookup, so the board power is supplied......I'll just have to switch it becasue the box will be sealed.

Looking at what I have, it may be dificult for me to finish this project with what I have. My garage door opener is 30 volt....bad.

I found a remote controll on ebay that uses the same voltage. Could I run my start/interupt with that instead? It has the same input voltage, but I'm not sure if I would hook the output of it directly to my input pin. Any help on this? Here is the link:
http://cgi.ebay.com/4-Ch-RF-Control...ptZRadio_Control_Vehicles?hash=item3359a99fe8

 

[(*steve*)]

*NO* *NO* *NO* NOT 9 volts!

Read the documentation -- it's a 5v device. Use 3 AA cells for battery operation (~4.5v)

OK, it might have an on-board regulator, but please make sure before you connect it to 9v. Most proto boards do not.

Yeah, that remote control should work fine. Both it and the Picaxe will run from 5v. The only possibility is that you might need a pull-down resistor from your chosen output to earth (10k would be fine).

The garage opener *might* be OK. The power supply might be 30V, but I'd not be surprised if the circuit operated at a much lower voltage, Alternatively, interfacing it should be no worse than a couple of resistors and maybe a couple of diodes.

Frankly, I'd get the program working on the picaxe now. Load up the software on your PC, make a trivial program to flash a LED and get familiar with it, then write (and debug) the software to do the timing.

It would help me if you can give me a link to the proto board you purchased.

 

[huntmaster]

ahhhh, I've not got things going yet. I see it now.

Think I've got it now. Been doing some reading.

Thanks again!