• Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Help! Display control board

Status
Not open for further replies.

iw4egx

New Member
Hello, i'm planning to realize a board that could show on bargraph's display some data of my amplifier.

i need to control:
0-1A plate current
0-100mA grid current
100-0-100mA tuning
0-30microA output power

i'm thinking to use I/V converter and LM3914 for drive led's.
Any idea of built this board?any suggestions?

Nicola
 

duffy

Well-Known Member
It's kind of a pain to do a bunch of current monitors on a high voltage line with LED bargraphs. Are you sure you wouldn't settle for a moving-needle meter? Heck of a lot easier to implement, and more precise besides.

Problem is your power for the 3914 has to be isolated from the plate and grid voltage. There's a couple of ways to do it, you can use a hall effect current sensor, a special linear opto (which needs 2 supplies), or isolate the 3914's with a separate transformer and power supply for each.

With a moving needle meter, it's just wired across a shunt resistor. That's it.
 

iw4egx

New Member
of course with moving needle meter is simply to realize but is not so beautiful :D

i have a separate transformer for the control board, i have to separate them anyway?optocouplers like CNY-74-4 or 4N25 are not suitable for this function?
thankyou very much
Nicola
 

Attachments

nike6

Banned
what about a LED dot matrix module,
either built from individual LEDs, or a ready-made module, together with a PIC?

for instance the 16f884 would be powerful enough, and it also has A/D channels.

I do not know the type of visual impression you are looking for, maybe just a small dot matrix, or LED chains like in the picture, covering the whole front plate. a small (green) 5x7 LED dot matrix would be very decent.
do you need to know exact current? maybe also add a small 8x2 LCD.
 

duffy

Well-Known Member
That does look pretty cool.

Problem with the CNY-74-4, 4N25 and almost every other opto is they aren't linear. Look at the hook in fig. 8 on the spec sheet -
http://www.electro-tech-online.com/custompdfs/2009/06/83526.pdf
- that's the collector current vs. forward current. Worse, the gain isn't repeatable from unit to unit.

Still, if you are only making one, maybe you could hand-tweak it, and try to use the more linear part of that curve.
 
Status
Not open for further replies.

Latest threads

EE World Online Articles

Loading
Top