Hey guys... and gals.

I'm trying to build a custom cable tester. I need the tester to be able to sequence output to 20 individual LED's. Now i know how to get the 4017 to cycle automatically through the use of the 555... what i don't understand is how i can get it to cycle... manually. I need to be able to switch between automatic and manual modes. I have a LAN cable tester that does it... but i haven't been able to dissect the circuit well enough to understand the process completely. I know the input to the 4017 is switched between the output of the 555 and a push button tied to a Vcc source. Is the 4017 set up to switch with every pulse of the 555 (which may output a .5-1 Hz signal)? Can the 4017 be set up this way?

Thanks in advance peoples...

 

Yes but you will need to add some de-bounce circuitry to your switch or your 4017 behavior will be unpredictable.
Check this
http://www.radio-electronics.com/inf..._flip_flop.php

 

How would that circuitry be used on one push button switch to switch between the two inputs to the de-bounce circuitry?

 

Sorry for the late reply, i forgot about this thread.

You will need a SPDT pushswitch for this circuit, if that is a problem there are dozens of other ways to de-bounce your switch.

Attached Images

4017.gif (7.5 KB, 24 views)

 

I believe this is the circuit you're after
http://www.mitedu.freeserve.co.uk/Ci...abletester.htm
Sorry this circuit looked a lot like the one in my cable tester, but this one needs a LOT of work to come close to the purchased tester.

 

I don't know if this will help but The attached diagram (PDF) is for a Molex/MOD TAP SLT3 UTP cable tester, they use 1 x 4051 and 1 x 4060 and a small reed switch in the case to shut it down when not in use.

Rather than pay some ridiculous price for this tool I have reproduced the circuit for both parts, you could house the sender and receiver in two small ABS boxes which can be bought for peanuts.

Good Luck, if you need further info. please advise.

Attached Images

	SLT3.gif (49.3 KB, 6 views)
	tester.jpg (39.3 KB, 3 views)

Attached Files

MOLEX_UTP.pdf (16.2 KB, 8 views)

 

I thought about using a three position switch to direct the ouput of the 555 either directly to the 4017, or optionally passing the clock to one of the inputs of a debounce circuit, made up of two NOR gates. Using a push button switch to manually cycle a link to Vcc to the other side of the debounce circuit. then tie the combined ouput of the gates to the input of the 4017 as well.

Make sense? Or am i way off...?

 

Erm.. not really, it's the switch you need to de-bounce, not the output of the 555

Try this , it's not as reliable as the first circuit but should be fine for what you want.

Attached Images

4017.gif (3.4 KB, 25 views)