Electronics countdown timer creation?

[Rook 3]

Just wondering how hard it would be to make a specialty countdown timer to replicate a demolition pack as seen on a TV series.

It would need to have:

-4 digit LED number system.
-Push button activated to input times in 00, 10, 20, 30 increments as well as minutes and seconds.
So feasibly you could set the timer anywhere from 30 minutes, 30 seconds... to as little as 10 seconds?
-Reset button? (the little - symbol?)
-Push button to activate.
-Perhaps a "beep" sound when it "goes off"?

Total PCB size shouldn't be any larger than 3" x 2" to fit in the casing shown above.

Any ideas how hard they'd be to make, and possible costs involved?

Thanks!

Russ

 

[leach145]

Have you done any electronics before?

 

[MFP 2020]

What's an ELAPS?

Also, that's the most colorful piece of "USMC" gear I've ever seen. Care to share what show it's from?

 

[madmanmoe64]

To do that you are going to need a micro processor. (a chip)

the Picaxe system is really easy to use and I have used it for similar projects.

the parts you describe are

4 x 7 segment display (60p) = £2.40
7 x tactile switch (13p) = £0.91
1 x piezo sounder = £0.08

you would also need

1 x picaxe chip = £2.99

stuff to download onto chip
and the handfull of resistors needed
£4.00

total = £10.38

realistically you may end up spending more (When i ordered parts I bought loads of stuff for experimenting / future projects)

If you are interested then read this

it introduces everything, I managed to pick it up quite quickly and there's a huge online community if you get stuck.

You might read it and find that you don't want to get into all that. But it's the easiest way of achieving what you want.


You could also use an arduino but they tend to need larger boards and the start up costs are a lot higher (£20 - £30 for initial unit)



Forum , manual pt.2 , pt.3

 

[Rook 3]

What's an ELAPS?

Also, that's the most colorful piece of "USMC" gear I've ever seen. Care to share what show it's from?

Don't you know? I mean it's ELAPS! It's... Um... Oh, heck, I don't know. :lol

I think perhaps it was supposed to be "Elapsed"?

Dunno for sure, I didn't print out the labels on set.

The picture is of a series used background demo pack from "Space: Above And Beyond."

PS: Good to see you over here from the MMMovies forum!

 

[exoray]

To do that you are going to need a micro processor. (a chip)

the Picaxe system is really easy to use and I have used it for similar projects.

the parts you describe are

4 x 7 segment display (60p) = £2.40
7 x tactile switch (13p) = £0.91
1 x piezo sounder = £0.08

you would also need

1 x picaxe chip = £2.99

stuff to download onto chip
and the handfull of resistors needed
£4.00

total = £10.38

realistically you may end up spending more (When i ordered parts I bought loads of stuff for experimenting / future projects)

If you are interested then read this

it introduces everything, I managed to pick it up quite quickly and there's a huge online community if you get stuck.

You might read it and find that you don't want to get into all that. But it's the easiest way of achieving what you want.


You could also use an arduino but they tend to need larger boards and the start up costs are a lot higher (£20 - £30 for initial unit)



Forum , manual pt.2 , pt.3

Well there is a little bit more to it then that, sure that is the core parts you could use but you need 28 outputs to drive the 7 segments, 32 if you use the decimal points... You can multiplex but that really complicates the code for a newbie... Or you can use drivers either on board or external to the 7 segments to reduce pins, but that comes at a cost... The straight forward route for the newbie will require 32 output pins, and the picaxe will be likely be over it's source/sink limits at that point requiring Darlington arrays or transistors so you don't toast the chip, or at least to keep it in spec...

You will need 7 more input pins for the switches and one more output for the buzzer, with at minimum a transistor so you don't over source/sink the pin... Again some trickery can be done to reduce pin count but at the cost of complicating the coding for the newbie...

Counting the pins up and you need a 40 pin chip if you don't use segment drivers, multiplex or use trickery to reduce the pin count...

Anyway it can be done but like I said there is more to it, and a newbie could get overwhelmed...

The cheapest and easiest solution is probably to purchase a 4 digit countdown timer kit, they are about $20... It won't be a perfect match to what you want but it will add lights...

If you want a custom drop in solution that is built to your specs, feel free to PM me it won't be as cheap as doing it yourself or kit bashing something over the counter, but then again you won't have to lift a finger, or soldering iron...

 

[madmanmoe64]

I was thinking about having a driver for each of the displays, but it was already a lengthy post and I didn't want to get into it.
Now I think about it, it's a lot to get your head around for a first project.

 

[Wes R]

You'll end up spending more just because at least in the US they charge a flat rate and its nuts to pay 7.00 shipping to only buy a handful of fairly inexpensive items so you may as well load up.

 

[leach145]

I think that you may struggle to mount the electronics you need on a PCB the size you require. I would suggest buying a timer similar and then adapting it from there.

 

[ShackMan]

Now I think about it, it's a lot to get your head around for a first project.

Not to put you off learning this stuff, but I'd agree ... as a first project, you'd probably be getting in a little over your head. As Exoray said, you could work some "magic" to reduce pin count, but that's even more advanced. Figure you could do this with 19 pins; fewer if you used some as both input and output.

Good luck, whichever route you take,


ATM
ShackMan

 

[exoray]

Figure you could do this with 19 pins; fewer if you used some as both input and output.

With charlieplexing you can get the 7 segments covered with 8 pins...

The 8 buttons can be handled with 4 more pins, and the buzzer can have it's own pin or could be plexed with the 7 segments...

In the end you can easily get down to 12 pins with some trickery and additional coding... You could probably drop an additional pin or two with additional segment driver ics...

 

[Fluxcapacitor]

All I know if be careful with it. Helped a friend of mine with some electronics for a fake bomb. Looked like sticks of TNT taped together with a digital timer, it made loud clicks, advanced a timer backwards in a countdown, had a toggle switchguard that once turned on can't be turned off. Well, a few were sold here and there to select people. One of them was in trouble with the law apparently and his "bomb" was found by police who called the bomb squad, and had the prop detonated as a precaution.

 

[jwrjr]

With the possible exception of the panel switches, the parts will be pretty cheap. The displays can be multiplexed, so (using a microcontroller) you will need 12 outputs for the displays and 8 inputs. Say ... $10 - $15 for the parts not including the switches. The cost will come in for programming the controller. Of course if you do that yourself then the expenses will be mainly for the parts only.