Down Counting Circuit With Reset?

[CircuitCurious]

Pardon my newbieness,

I'm trying to build a shock sensor which will record each time there is a big enough shock. I'd like it to start at 10, and count down to 0. From what I've understood thus far, having 2 segmented displays would be easiest. Further down the road, I'd like to have the leading 0 be a blank (10, 9, 8, 7... rather than 10, 09, 08, 07).

I'd really like some reading material and maybe a wiring schematic. I want to understand the chips, and how they work, rather than assembling what others have conceptualized.

From what I've found so far, I could use 4000 series chips (4029?) or 70000, although I'm still not too sure what exactly I'm looking for.

 

[Diver300]

You could start with an up/down counter, set to count down. Connect that to a BCD to 7 segment decoder.

A CD4029 is a counter that can be used as a BCD up/down counter.

CD4511 or CD4055BE is a BCD to 7 segment decoder.

 

[CircuitCurious]

So a 4029 doesn't have much of a difference with a 74192, does it?

So I should use a 4029 up/down counter, would I be able to have it start at 10 right away? Or would I have to go up to 10, then work down with my shock sensor?

I could use a rapid firing 555 timer to upcount back to 10 if there is no reset. I'm still not understanding everything all that well.

 

[Diver300]

The 4029 is presettable. If you put 10 (1010 in binary) on the preset lines, the count will jump to 10 when you raise the preset line.

You could use two digits, so two 4029s and two 4511s to give you the two digit display. It's a bit of a waste as one digit only ever shows 1 or 0 but it's probably less ICs than other solutions.

The CD4511 has a blanking input that turns off the whole display, so that 0 - 9 are shown as single digits. You need some kind of logic to feed the blanking input.

 

[Reloadron]

So a 4029 doesn't have much of a difference with a 74192, does it?

So I should use a 4029 up/down counter, would I be able to have it start at 10 right away? Or would I have to go up to 10, then work down with my shock sensor?

I could use a rapid firing 555 timer to upcount back to 10 if there is no reset. I'm still not understanding everything all that well.

The big difference between the 74192 and the CD4029 is the working voltages. The 74192 Data sheet here and the 4029 Data sheet here is the 74192 is a TTL logic device running at 5 volts and the 4029 has a Wide supply voltage range 3V to 15V.

Both chips allow a count up or count down (using either) there is no need to count up before counting down. Both chips allow a preset meaning if I want to count up to or down from 5 I can easily do that. Both chips can be cascaded for higher counts.

Something to note is counting down from 10 is really counting down 9 through 0 (ten counts). Both chips can be setup to either count up or down and stop or recycle.

<EDIT> Diver beat me, sorry. </EDIT>

Hope that helps.

Ron

 

[CircuitCurious]

Thanks for the excellent advice guys. I'll try and get a schematic worked out. I'm hoping to eventually have something more sophisticated, but this will do for now.

 

[CircuitCurious]

Quick question, everywhere I read, it says that the 4029 has to do with clocks. My circuit has nothing to do with time, or clocks. Is this some sort of term?

EDIT: Clocks are 4029 circuits, is this correct? My mind is blown.

 

[Reloadron]

Clock is just a term. For your purposes we could as easily say pulse. Your "shock" is a bang exceeding a certain level. Each bang produces a pulse (clock pulse) that decrements a counter down a count.

Attached is a circuit using a pair of 74192s that are cascaded to provide an Up count. The circuit you want would be similar but configured to down count. Though not what you want, it should present an idea of how it is done. Just an old circuit I had.

Ron