Breaking News
Comments
Newest First | Oldest First | Threaded View
Max The Magnificent
User Rank
Blogger
re: Men versus Women: Help required controlling meters!
Max The Magnificent   3/5/2009 2:26:10 PM
NO RATINGS
Thanks for the input -- I agree about the PWM -- and also the way you were talking about doing it (register, counter, comparator) -- in fact I'm going to use a cheap-and-cheerful 50 cent PIC for each meter to implement the PWM -- each of these PICS will be told what to do by my PICAXE ... still fine-tuning the details. Cheers -- Max

Bob Lindner
User Rank
Rookie
re: Men versus Women: Help required controlling meters!
Bob Lindner   2/26/2009 3:20:10 PM
NO RATINGS
You can use a resistor ladder network much like D to A chips do.

EDW
User Rank
Rookie
re: Men versus Women: Help required controlling meters!
EDW   2/19/2009 4:21:44 PM
NO RATINGS
Also, you might want to put your LEDs in a XY grid and multiplex them. LEDs are more power efficient when multiplexed, and you would drastically reduce your IO pin count & wiring.

EDW
User Rank
Rookie
re: Men versus Women: Help required controlling meters!
EDW   2/19/2009 4:17:48 PM
NO RATINGS
All meters are basically a spring loaded coil of wire placed in a magnetic field. Input current causes a magnetic force, which balances with the spring force to produce a equilibrium position. To make it read bigger amps add a low shunt resistance. To make it read volts add high series resistance. In your case I think you should not use any shunt resistance (so as to limit the power dissipated by the meter) and only use series resistors. Take the PIC output voltage and apply it to the meter with a 1 meg pot in series (set to max resistance!). Dial the pot down until you get full deflection, then measure the pot with a DMM and put a fixed resistor of this value permanently in series with the meter. You might want to add a fixed resistor to your test setup, say 10k or so, to prevent accidents from happening. Have you considered using PWM for the meters? Even a simple first order PWM should work fine. This would give you very fine grained control of the meter position and would drastically reduce pin count and external components. In CPLDs and FPGAs I implement PWM via an up-counter, a comparator, and a register. if the up-counter is less than the register value, make the output high. If it is greater than or equal, make the output low. If the clock into this process is fast enough the meter will act like a low pass filter and display a steady value. To use a slower clock, add a capacitor to the meter. Width (bits) of the counter and register determine the resolution. For audio you should use at least a second order modulator in order to obtain reasonable clock speeds and low noise floor.



Flash Poll
Top Comments of the Week
Like Us on Facebook
EE Times on Twitter
EE Times Twitter Feed

Datasheets.com Parts Search

185 million searchable parts
(please enter a part number or hit search to begin)
EE Life
Frankenstein's Fix, Teardowns, Sideshows, Design Contests, Reader Content & More
Engineering Investigations

Air Conditioner Falls From Window, Still Works
Engineering Investigations
Post a comment
It's autumn in New England. The leaves are turning to red, orange, and gold, my roses are in their second bloom, and it's time to remove the air conditioner from the window. On September ...

David Blaza

The Other Tesla
David Blaza
5 comments
I find myself going to Kickstarter and Indiegogo on a regular basis these days because they have become real innovation marketplaces. As far as I'm concerned, this is where a lot of cool ...

Max Maxfield

Feast Your Orbs on My Jiggly Exercise Machine
Max Maxfield
54 comments
Last weekend, I was chatting with my mother on the phone. She's all excited that I'm coming over to visit for a week in November. "I'll be seeing you in only seven weeks," she trilled ...

Larry Desjardin

Engineers Should Study Finance: 5 Reasons Why
Larry Desjardin
47 comments
I'm a big proponent of engineers learning financial basics. Why? Because engineers are making decisions all the time, in multiple ways. Having a good financial understanding guides these ...