Timer Project, LED Display

Nightmare

It's been years (about 8) since I used my Basic Stamp.· My last project was a digital speedometer for my ATV.· I have the smaller BS1 from about 2000.
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I'd like to make a new project.· I'm sure someone else has completed the majority of the leg work.· I tried to search the forums for the items I need, but I didn't find much.· Here is a breakdown of what I think I need.· Any additional advice is appreciated.
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I want a timer (like a kitchen timer) that will count down from a variable number of minutes.· I want to output the time to a set of 4 large LEDs (they are 7-Segment common anode).· When the timer reaches zero, I want it to sound a piezo siren for about 10-20 seconds.· After that time the program can end.
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Here is my basic plan:
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1)···· How to set the amount of time?· I figure a DIP switch should make it easy to change the time on the fly.· 8 segments will give me up to 128 minutes.
2)···· I need the count down package.· I can add a clock (like a 555 timer) if necessary, but I don’t need it to be super accurate.· If the Stamp can keep it within 5-10 seconds over 10 minutes then I will skip the external clock.
3)···· I think I will need a controller chip to drive the LED display.· I’m going to start with just 4 LEDs (I might add 1/10 and 1/100^th of a second later).· I used a serial LED display in the last project.· Can the Stamp drive the LEDs without a controller?
4)···· The siren should be easy to setup.· Can I drive the siren through the Stamp, or should I have the stamp trip a relay?
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My hope is to find these 4 components and then just get them to work together.
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Thanks.

T&E Engineer

You can definately do this timer project on a BASIS STAMP 2 (BS2) but I'm·not so sure about a BS1. However, you will need a LED driver chip. The most well known chip used with BS2's on this forum is the MAX7219 and there are lot's of examples for you to do your search· on. This will·drive up to 8 LED displays (or 64 individual LEDs)·and you only need 4 LED displays.

Another idea is to use a Parallax SX-28 as the LED driver.·Download this SXB online manual and look at the example on page 242 towards the bottom. It is an SXB Example of a clock/timer which is what you want·with the exception of the alarm. If you already have some BS1 experience, it may be time to jump on the SX-28 bandwagon as learning SX/B (Basic)·is not that much·harder than PBASIC for the Basic Stamps.

http://forums.parallax.com/attachment.php?attachmentid=47155

Finally as another alternative you can check with BEAN (Terry Hitt) about these displays·he once sold and may be out of. I bought·4-5 as he originally sold them for $5 each over a year or more back. It was a·4 digit display·(with on board driver) that easily interfaced with a Basic Stamp 2 or SX chip. It was called the HC4LED and do a search on the forum for examples.

http://forums.parallax.com/showthread.php?p=640378

http://forums.parallax.com/showthread.php?p=630830

or others.

Here is his website (but did not see the HC4LED) - but he may have a couple of them available still.

http://www.hittconsulting.com/

Good Luck.

·

RDL2004

www.hittconsulting.com/miscforsale.html

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- Rick

Nightmare

I saw that HC4LED at his web site.

I already have 6· 1.8" LEDs.· I want something you can see from across the room.· The HC4s are only .39" tall.

T&E Engineer

Well the MAX7219 is for Common Cathode LED displays and you have Common Anode LED displays so this solution is out of the question. You could always use inverters (7404) but that would be alot too.

I beleive the SX-28 example is for common cathode LED displays too - but it could be modified in the code with probably not too much difficulty.

Nightmare

I just found some 1.8" and 2.3" LEDs Mounted on a control board on Ebay for about $10. I think I'll purchase that and save some soldering [noparse]:)[/noparse]

In the mean time I think I'll try to get the rest of the project running with my LCD Display (the serial one from my Speedo).

I'm also re-thinking the DIP switch to set the time. I wonder if a push button to add time might be easier. I'll only need whole minutes to start the clock.

PJAllen

http://forums.parallax.com/showthread.php?p=724122

Nightmare

Thanks for that link. I've ordered a 4 digit 7-seg display with a controller board. It's only $10 and should save me a lot of work [noparse]:)[/noparse]