Hi PK,

We’d really appreciate some help to design a 60 to 0 second display timer for our Low Power Controller.

We wanted to add a visual layer of protection for our newer and younger members in the event they encounter a mis-fire. A large digit display counting down from 60 seconds will really help them see how long 60 seconds really is, or isn’t before they approach their rocket to investigate.

We will mount this to the inside of the lid of the controller (box on the left) so it is clear view of the Launcher and LCO.

Could you please assist with the design of the circuitry to drive this as well any hardware procurement tips ?

Regards,

Hi Rob,

I have seen countdown timers over the years in Silicon Chip Magazine. Will see if I can find one in my back issues. Jaycar have a kit you may already be able to use, and by using Jumbo 7 segment displays, it may do what you want already! It is Catalogue Number KC5496 and is only $40! All the hard work is done for you!

The challenge here though is to make something that can be triggered by a variety of launch controllers, has large bright digits, and has logic that's compatible with the application.
eg if the countdown is triggered by an attempt to launch, then it should reset to 60 seconds if the LCO (because we all know it's not safe to let someone launch their own rocket right?) retries. In practice, you'll end up grafting a micro onto that kit to get it to do what you want. Then you'll graft on some big displays....
If you're gonna use a micro and big displays then you don't really need the kit..

We just happen to have a couple of hundred 100mm tall, ultra bright, LED digits in stock. I'll have a quick tinker...

PK

Here's a cheap one you could use :
http://www.teachersparadise.com/c/onemi ... -1817.html

Whooshtronics presents, the "Safe-o-Matic" !


So I had a bit of a play this morning:


As you can see, it's mostly about the mounting and display units.
The actual processing and driving of the display is all done by the micro...
Here's the first cut at it:


Now I stuffed up one thing; I was hoping to get away with a 3 terminal linear regulator to drop the 12V launch control supply down to 5V for the display modules and micro. I forgot how much current these displays draw!
With all segments lit the system pulls just shy of 800mA, that's 5.5W dissapation from the reg. Now I could just bolt it to the metal case and hope for the best, but it'd all get a bit toastier (think QLD summer sun on the box) than I'd be happy with. Not being a big fan of marginal power supplies, I'll re do it with a switch mode supply and it'll be solid.

The panel is designed to go into a stock metal box from Altronics, I'll grab one this week. Assembled she looks like this:


I tried to get a good shot of it running indoors, but it's soo bloody bright that this is the best I can come up with:


Oh, and I added an output to turn on an alarm or strobe too. Just in case having your retinas burned out by the displays isn't enough to dissuade you from approaching the pads!

More soon!

PK

Nice work PK!!
Fast ,simple and effective. But can you make it do a verbal countdown????

Also we need to build a time machine....what do wooshtronics have ???? oh and we need it yesterday !!

I actually have a couple of voice recording/playback IC's, but they are set aside for the Zap-o-matic!


You already asked that question tomorrow and your order was shipped 21/11/2090!

PK

Thanks PK I'm Unwrapping it now.

If I can just find the start of the Möbius strip you tied it in........

Doesn't everyone know that CGN has invented "Time Travel"© http://www.cgngroup.com.au/news/2012/ and now rules the world?

15 years in the making mind you

You've always been the impatient one!
PK

Hi PK,

Many thanks for working on your Sunday for us, we really appreciate this. I love the name; "Safe-O-Matic"

I see what you mean regard the display, it will be visible in the bright Brissy sun. In Winter we'll need to wear sunnies

Regards,

Some Progress
Apologies, some work travel got in the way of this project, and probably will do again this week...
And then there's the heat!

The switched mode power supply version of the controller board is complete:


and the case arrived.

First job was to machine out the lid supports so that the laser cut acrylic could sit inside.


Then I threw some paint at it.


A 1/4"UNC tapped hole in the bottom means it can sit on a tripod....Seemed like the best way to mount it..

More soon..

PK

Again a huge thanks to PK for his efforts with this misfire countdown timer. I got around to wiring it into the existing QRS LPR controller on Saturday before the launch and after a few minor hiccups, the system came alive almost blinding me from close range

A seperate button was installed into the controller (yet to be labelled) which operated independently to any other circuits. This means it can be triggered when using other systems without having to turn on anything on the LPR controller.

Works beautifully !