Hello everyone....another project.
Thanks for helping.
I need a digital count up timer that shows ...seconds....tenths of a second and 100ths of a second...
The timer should have numbers about 8 inches high...and be in red..and would count up from zero.
The timer should be 110 vac.
I cant find anything on the Internet less than about $300.oo...that seems like a lot.
How cheaply can I build one of these?
D.

 

You did not specify the maximum display value.
Assuming the max is 99.99 seconds then you need 4 digits.

Total cost is for components is about $100.

 

$100 sounds about right for parts, but what is your time worth. If you design and build electronic assemblies for a living, then your final product probably will look like a commercial unit. If this is your hobby, then be prepared for weeks of effort and more than a little bit of frustration. Not that that is a bad thing at all. Getting there can be *all* the fun. But little things like getting the rows of LEDs in each digit segment to be in a straight line take surprising amounts of time.

The circuit can be all discrete (or even all analog parts), counters and gates, a microcontroller... just about anything. Or, you can buy an electronic stopwatch kit for the brains and adapt it to your larger display. How do you want to do it?

ak

 

Hello....

USD 100 is a nice budget in parts for such an project, and I assume that this includes an enclosure and a piece of red perspex cut for the display on the front panel? Some nice front panel artwork too. You do want the box though right? You don't just want an circuit board?

OK...

I would use an microcontroller and use its interrupts timer for precision. But I would first start with the box and front panel artwork. The outside look of it defines what the inside layout would be like. Normal people do not look inside the unit... They only see the outside!

 

how about something like this, if you clock it at 100Hz, it will count up and display to 1/100 second, you can make a clock or xtal ,and gating using a 555 timer and cmos chips.


http://www.ebay.co.uk/itm/271266668437?redirect=mobile

 

If you need the timing to be accurate over a prolonged period then a 555 timer won't cut the mustard. A crystal-controlled clock source is called for.

 

Take a look at this thread for some ideas.

All is doable. As Mr. Chips mentioned, we'll need to know how many digits you want. If you want to make it super cheap, you can use 5mm red LED's and make the digits yourself. If you want cheap but lazy, you could use LED strips to make the segments.

Is this going to be used indoors or outdoors? If the latter, will it be viewed during the day in full sunlight or in the evening (dark) or both?

 

Hello...

Keep in mind that you need to start with the project BOX. Do the front panel artwork first. The look and feel of the outside defines what goes inside the BOX

 

Thanks, everyone. ...and hello to Mr. Chips and Elect Mech....been a while.
I'm making a game for my county fair.
The specs have changed.
I need 2 counters.
Both should be in a box that could be rained on without damage.
The boxes should be about 16 inches long, 8 or 10 inches high and ....I guess 4 or 5 inches thick......or close to that.
Both should operate on 12 vdc ....(previously I said that I needed 11ovac)
The ambient light will be similar to a county fair midway......the game will be played at night.
Neon Green numbers would seem to be good but I dont know......they may not be available...
The numbers should be visible for 30 feet or so....I thought 8 inches high would be fine....don't know.
I guess I need 4 digits and a decimal...(would that be 5 digits?)
Secs 0-9.....secs 0-9...... 1/10ths sec......1/100ths sec (example) 36.75 ...thirty six and seventy-five 100ths seconds ...the decimal is a must....so maybe that would be 5 digits.
The box should have a terminal strip on the back so I can ....Start the counter...... Stop the counter..... and.... Reset the counter with an external switch.
The style above that was mentioned in the link from dogydave looked good....
If anyone wants to give me a price for these, I'd be glad to entertain it...
The Fair is in the Fall of Oct. 2015 so we have plenty of time to talk...
I dont want to build these myself...
Darryl

 

If anyone wants to give me a price for these, I'd be glad to entertain it...
The Fair is in the Fall of Oct. 2015 so we have plenty of time to talk...
I dont want to build these myself...
Darryl

USD 5K to engineer and build a unit. Includes copyright and all project files.

 

The boxes should be about 16 inches long, 8 or 10 inches high and ....I guess 4 or 5 inches thick......or close to that.

Doable with boxes rated for weather/waterproof. I haven't done this before, but you could get boxes with clear lids then mask off the digits within the box and paint the rest to give it a more polished look without a lot of work.

Both should operate on 12 vdc ....(previously I said that I needed 11ovac)

A 12VDC wall wart or are thinking of a battery? If the latter, it needs to be big as LED's will consume a lot of current in a few hours.

Neon Green numbers would seem to be good but I dont know......they may not be available...

If you're looking for COTS then you have your choice of red, green, or blue depending on how big you want them or how much you wish to spend. It's cheaper parts-wise to build your own using thru-hole LED's or perhaps LED strips, but if you're going to pay someone else, you're probably better off buying pre-made digits to save on labor.

The numbers should be visible for 30 feet or so....I thought 8 inches high would be fine....don't know.

I did a test a year or so ago. Four inch digits could be seen close to 75 feet away. So for 30 feet, you could use 4" digits which don't cost too much if you only need low light ones (work great in the dark, near invisible in direct sunlight).

The box should have a terminal strip on the back so I can ....Start the counter...... Stop the counter..... and.... Reset the counter with an external switch.

If it's going to be rained on, I assume this strip will go inside the enclosure.

What will you use to trigger the counter? Push button switch or something else?

Having burned myself the last time I attempted to build a project for someone here, I'm remiss to take this on myself. I can assist with the design and parts selection if you find a capable builder.

 

Ok Elec mech....
I'll take you up on your offer to help.
I appreciate it very much.
The first question I have is WHERE do I get 4 " pre built numbers or the led strips that you mentioned?
I cant find anything on the Internet....
Darryl

 

6.5" LED displays:

https://www.sparkfun.com/products/8530

4" Kingbright LED displays:

http://www.newark.com/kingbright/sc...d/dp/26M2944?MER=PPSO_N_P_EverywhereElse_None

 

Thank you, Mr. Chips....
BTW..are these LED displays something that I can use with an Arduino PLC ?

 

Elec Mech.....I sent you a PM.
D.

 

Thanks MCU88 ....but I couldn't afford more than $4999.00
Thanks for the offer though.

 

Thanks MCU88 ....but I couldn't afford more than $4999.00
Thanks for the offer though.

Most amount of money I have ever received from someone for doing an project was AUD 1,700. Arh you don't want a project from me anyway. As someone pointed out I don't comment my C source code. Might send the next person round the twist, if you pass the project files onto someone else to dust, polish or modify in years to come. I might not be around you know.

 

Another option for pre-built displays here. Per your PM, yes you can build these yourself for much less. Below are some pictures of homemade displays using just thru-hole LED's and 1/8" thick plastic as a base (acrylic works well, but personally I like PVC). The red display is made with a single row of LED's per segment while the green one is made with two rows per segment. So there a lot of DIY options. You can buy bulk LED's from eBay pretty cheap - the trick is picking the right brightness based on the environment. If only used at night, then diffused LED's will work best (won't blind you). However, green diffused LED's are never bright enough, so you'll want to use high-brightness for green if you go that route. We'll help you pick out the right type if you decide to go this route.

I haven't heard of an Arduino PLC before, but if you're referring to a standard Arduino, yes, you should be able to make it work with any LED 7-segment display. If you plan to have the Arduino control the displays, then I'd suggest looking at a MAX7219/21. It is a pricey IC at about 11 USD, but it will control up to eight digits with a minimum of wiring and only need 2-3 I/O pins from the Arduino. You could probably accomplish the whole circuit in digital logic only if you want as well. I don't know what kind of accuracy you'll get from an Arduino if you want to get done to 1/100th of a second. Might work, might not - I just have never tried this with a uC.

If you don't mind, I'd love to share your project description on the thread - I think other members would be interested to hear what you're doing and may be able to offer more advice.

 

EM....
OK...that would be fine to show everyone what we are doing...I'm sure I'll be asking some very basic questions as we go along with the project, so there's that.
Let me digest your last post and get back to you with a question or two.
BTW...what if I wanted to draw something on plain paper, scan it and include it with my post to you....are there instructions on how to do that on this site somewhere.... or is this just regular computer knowledge?
I'm sure I can figure it out with a few questions.
D.

 

BTW...what if I wanted to draw something on plain paper, scan it and include it with my post to you....are there instructions on how to do that on this site somewhere.... or is this just regular computer knowledge?

It's pretty straightforward, but you can skip a step if you just want to take a picture of the drawing with a camera (standalone or a smartphone if you have one). A camera will save the image as a JPEG which is easy to post here. If you want to go the scanner route, you shouldn't have to do much, those are usually saved as JPEG's or similar - shouldn't need to convert the scan to anything else to post here. To post, just click on 'Upload a File" at the bottom of screen when you write a post and select the location of the image. Let us know if you run into problems.

All,

Here is a description of the OP's project in detail:

"The Pit Challenge"
I'm building a tire changing game in which each of two contestants use an impact wrench to take off a tire ........set it on a switch pad......put the tire back on and tighten up the lug nuts using their wrench.
To start their respective timers, each contestant takes an air impact wrench out of a "shoe" that contains a switch.
When the wrench leaves the shoe, the timer starts and when the wrench is put back in the shoe, the timer stops.
The contestant must completely take the tire off the hub and set it on the switch ....when that happens, a light will light up letting everyone know that the tire has been "completely taken off the car". The switch pad is momentary and the light will be momentary.
I'll have a mock up of a race car on a trailer, etc...
Somewhere there's got to be a flat bed trailer in this deal or it wouldn't be a country fair...