New member-looking for some help!

[haggisbasher]

Hello everyone,

I'm a graduate of electronic engineering and have just started my first job so bear in mind I'm quite new to all the tech talk etc.

I'm looking for some help on a project i'm working on at the moment where i'm involved in designing a test system for a simple 12V activation system. The test system has 14 BNC O/P's, which are for reading the voltage activation pulse on a scope at each channel, each channel is activated in succession by one manual switch action. The bit i'm stuck at is that I have to design a small internal latch system that keeps an LED light (one LED for each channel) on as each channel is activated firstly by the switch > PIC/control > relays. The test system interfaces into the system with the input being via a 19 way socket from the control system and the voltage O/P via the BNC O/P's.

Can anyone help with the design of a simple latch system or even any pointers where to start and IC's to use.

Thanks for any help.

HB

 

[VEBill]

If you're designing a test station (for production test?), it is well worth it to make it as fully-automatic as possible. This would mean using a scope that can be PC controlled, and controlling your relays with a discrete output card in the PC.

Creating your own circuit from scratch can easily cost more by the time it is done than a PC-based, fully-automatic test station.

 

[haggisbasher]

Thanks for the reply,

The product is really only a one-off at the moment and if it goes into production the testing will become more automated and TBH I doubt I could design an automated test station with my limited experience at the moment. What i'm trying to figure out at the moment is how to make a holding/latch circuit that will illuminate an LED to signify a 12V pulse...hopefully using some logic IC. Even if it doesn't get used in the test circuit I hope to have learned something and have something to keep me busy.

Regards

HB

 

[VEBill]

Can you simply wire the indicator LEDs in parallel with the relays' coils so that when a relay is energized, the matching LED is illuminated?

(I suspect that I've misunderstood your requirement.)

 

[fangas]

Hello HB,

The simpliest IC latch is the RS NAND. Try this site:

http://www.play-hookey.com/digital/rs_nand_latch.html.

Look at the RS NAND heading

go from there

ED

 

[buzzp]

If the pulse is supposed to keep something latched 'on', the obvious choice is a 'latching' relay. They only need one pulse to turn on and stay on. Reset can be manually or via another pulse. If the LED is only on when the button is on, then a standard relay will work.
Only word of caution is to make sure the coil of the selected relay can be driven from whatever source your using (ie logic circuits generally can not drive relay coild directly, have to use transistor to switch the relay coil).

 

[SolderingGunslinger]

And WHAT pray tell is wrong with Haggis, Haggisbasher? :-D
While the canned version of the National Dish of some of my ancestors leaves a lot to be desired, the real deal is wonderful, specially witgh copious amounts of single-malt...then again my other ancestors ate Lutefisk and Lefse and washed it down with aquavit!

Do you want a single button which will step through each output or do you wish one button per output? I guess I'm having trouble understanding just what you wish to do.

If you wish to have one button do the switching, string a bunch of flip/flops and be sure to de-bounce any mechanical contacts. Better yet, use a Hall Effect push button (they don't bounce). If you wish to scan through each channel, use an astable multivibrator. (Early scanning receivers like the Peterson Radio and Elektra Bearcat used a circuit similar to this)

Get a good circuit anthology book and analyze how some of these things are (were) done. No point in reinventing the wheel.

I remain,

The Old Soldering Gunslinger