Suggestions on external LED display

[imlost]

Hi,

I'm looking for an external 4 digit display. The display will have of course a Vdd, gnd, Data_in, and Clock_in.

I need to be able to drive the clock with at least 1khertz, i would to drive it at 10khertz. The reason is i need the display to be counting in milliseconds. I've found a few Digit LED counter but they don't really mention how fast they can count.

For example:

**broken link removed**

That one would be ideal if the counter can increment in milliseconds.

Any suggestions would be apperciated!

Thanks,
lost

 

[cowana]

You won't be able to read the display if it is counting in milliseconds - can you not just only display the numbers once the timer has been stopped?

 

[imlost]

Ah sorry i should have phrased that better. You said it pretty much how i want it. Count in milliseconds then display it

 

[Reloadron]

From the data sheet of the device you linked to:

The counter is triggered by a negative edge on its
CLOCKinput. That is, the CLOCK positive pin is
momentarily connected to ground. The Clock input is
debounced in the software to prevent false triggering
when mechanical switches inputs are used. The debounce
time is approx 15msec for each low/high or high/low
transition, giving a maximum count rate of 30 to 35 counts
per second. The counters may be easily mounted together
so the displays can merge together. You can work out for
yourself how many months this dual unit will count for
before an overflow is generated.

The max count rate of 30 to 35 counts per second does not come close to the 1,000 counts per second that you want.

Ron

 

[imlost]

haha ya i read that. So i was hoping some one might know of another counter/display combo.

 

[Reloadron]

I don't know of a module off hand but one could be built pretty easily using discreet components. The module you linked to might work with some modification to the input. If you just plan to run a 1 KHz clock into it you don't care about the switch bounce portion which seems to be the stopper.

Ron

 

[imlost]

So i just got this email from support about this product and this is what they said:

The limitation would be the speed of the I2C bus which is 400kbit/sec. Now,
it is depend if you want to update all 4 digit at 0.1miliseconds or just 1
digit. Each digit need 8 bits of data. So here is the absolute max speed.

Update all 4 digit plus one control byte. That is total of 40 bits. With
400kbit/sec bus then the 10kHz would be the absolute max speed.


Any opinions on that?

 

[Reloadron]

I believe they said it would work. I am not familiar with using a uC for apps like this.

You mention 1 KHz with 10 KHz preferred.

What you want could be done with discreet components with no problem. The down side is obviously more parts. The beauty of using a micro-controller is it gets the parts count down and makes for a simple board. The uC downside is how fast it can count the incoming pulses (Frequency).

Ron

 

[jbeng]

Take a look at the MC14553 from ON Semiconductor. Add displays, a 7-segment decoder/driver chip and a few other components and you have a three-digit up counter/display. If you would like more than 3 digits (you said in your original post you wanted 4) they can be cascaded. Digikey sells the chip for $2.50US.

Find a data sheet here: MC14553B

Obviously, this is dependent on if you know enough about electronics to build the counter/display system yourself.