If you need assistance, please send an email to forum at 4hv dot org. To ensure your email is not marked as spam, please include the phrase "4hv help" in the subject line. You can also find assistance via IRC, at irc.shadowworld.net, room #hvcomm.
Support 4hv.org!
Donate:
4hv.org is hosted on a dedicated server. Unfortunately, this server costs and we rely on the help of site members to keep 4hv.org running. Please consider donating. We will place your name on the thanks list and you'll be helping to keep 4hv.org alive and free for everyone. Members whose names appear in red bold have donated recently. Green bold denotes those who have recently donated to keep the server carbon neutral.
Special Thanks To:
Aaron Holmes
Aaron Wheeler
Adam Horden
Alan Scrimgeour
Andre
Andrew Haynes
Anonymous000
asabase
Austin Weil
barney
Barry
Bert Hickman
Bill Kukowski
Blitzorn
Brandon Paradelas
Bruce Bowling
BubeeMike
Byong Park
Cesiumsponge
Chris F.
Chris Hooper
Corey Worthington
Derek Woodroffe
Dalus
Dan Strother
Daniel Davis
Daniel Uhrenholt
datasheetarchive
Dave Billington
Dave Marshall
David F.
Dennis Rogers
drelectrix
Dr. John Gudenas
Dr. Spark
E.TexasTesla
eastvoltresearch
Eirik Taylor
Erik Dyakov
Erlend^SE
Finn Hammer
Firebug24k
GalliumMan
Gary Peterson
George Slade
GhostNull
Gordon Mcknight
Graham Armitage
Grant
GreySoul
Henry H
IamSmooth
In memory of Leo Powning
Jacob Cash
James Howells
James Pawson
Jeff Greenfield
Jeff Thomas
Jesse Frost
Jim Mitchell
jlr134
Joe Mastroianni
John Forcina
John Oberg
John Willcutt
Jon Newcomb
klugesmith
Leslie Wright
Lutz Hoffman
Mads Barnkob
Martin King
Mats Karlsson
Matt Gibson
Matthew Guidry
mbd
Michael D'Angelo
Mikkel
mileswaldron
mister_rf
Neil Foster
Nick de Smith
Nick Soroka
nicklenorp
Nik
Norman Stanley
Patrick Coleman
Paul Brodie
Paul Jordan
Paul Montgomery
Ped
Peter Krogen
Peter Terren
PhilGood
Richard Feldman
Robert Bush
Royce Bailey
Scott Fusare
Scott Newman
smiffy
Stella
Steven Busic
Steve Conner
Steve Jones
Steve Ward
Sulaiman
Thomas Coyle
Thomas A. Wallace
Thomas W
Timo
Torch
Ulf Jonsson
vasil
Vaxian
vladi mazzilli
wastehl
Weston
William Kim
William N.
William Stehl
Wesley Venis
The aforementioned have contributed financially to the continuing triumph of 4hv.org. They are deserving of my most heartfelt thanks.
Registered Member #51
Joined: Thu Feb 09 2006, 04:17AM
Location:
Posts: 263
Id like to build a strobe light (for a time fountain). I assume i will aim for something in the range of 10-20 hz output frequency. Two questions: 1. Does anyone have experience using a tl494 this "slow"? and, 2. Is there any good way to get a variable duty cycle and variable frequency signal out of a microcontroller short of using a D to A converter and a VCO?
Registered Member #509
Joined: Sat Feb 10 2007, 07:02AM
Location:
Posts: 329
I'd use the cheapest micro with enough programming space for you to do what you need. I would think about a PIC12F or a smaller 16F chip if you like to work with PICs and not AVRs :p
What kind of accuracy do you need? I would imagine accuracy isnt super important, for this. (I.E. If its set for 15 hz and actually outputting 14.8 hz, not a big deal)
I would take a PIC with a Timer1 external input, feed that with a low frequency (2-5khz or so) pre-load timer1 with a value, wait for it to overflow, and load the next value in the ISR, repeat... etc
Then a few multiplexed buttons that are scanned a few times a second to control it, dutycycle up/down, period up/down. etc.
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3141
If all you want is a constant repetition rate that can be preset, then a 555 would be good enough.
I suspect that for a stable time fountain it's best to synchronise the timer with the falling drops so a photo-gate is required for best results, again a 555-based system could work.
Ultimately a microcontroller would give the most flexibility with a crystal controlled clock no external timing/frequency reference is required.
Registered Member #51
Joined: Thu Feb 09 2006, 04:17AM
Location:
Posts: 263
Id like to stay away from a 555 as i want to be able to control frequency and duty cycle independently. I had planned on using an AVR if possible, i actually have some experience on them, vs. none on a PIC. I do have some of each here tho, and programmers for them. I really like the idea of a microcontroller but it still looks like there is no easy way of generating a digitally variable frequency without feeding a VCO from the micro...
Registered Member #27
Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058
Even the cheapest micrcontroller can make a variable frequency/duty cycle adjustable to one microsecond. In your case you get an accuracy to 1 in 50 000. A few hundred times more than you really need, unless your water is a special stable type.
Registered Member #51
Joined: Thu Feb 09 2006, 04:17AM
Location:
Posts: 263
Thanks for the help guys, I'm using a Tiny2313 as i have some of these on hand. Its working great. When my fountain is done (currently waiting on the pump to arrive) ill be sure to post in the project section and share my design.
This site is powered by e107, which is released under the GNU GPL License. All work on this site, except where otherwise noted, is licensed under a Creative Commons Attribution-ShareAlike 2.5 License. By submitting any information to this site, you agree that anything submitted will be so licensed. Please read our Disclaimer and Policies page for information on your rights and responsibilities regarding this site.
Strobe light with Tl494 or AVR microcontroller?
