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 #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
i know what a schimdt circuit does and is for, i dont see why this circuit is resistant to being smoked? please elaborate ? (maybe im just slow)
ok the ddsigner of this circuit is clear that he means for the inputs to be fully on or off and nowhere in between. so with the npn and pnp pair are alternatley driven on and off from the same logic line, due to polarity.
Registered Member #3900
Joined: Thu May 19 2011, 08:28PM
Location:
Posts: 600
Try to isolate just one leg. The other is irrelevant as it's just a copy of the first. Under what conditions will one npn/pnp leg shoot through? If the input signal is maximum then the npn will conduct and the pnp will not. If the input signal is minimum the the pnp will conduct while the npn doesn't. But what about the analogs in between? The pnp will have current flowing out of its base and into the signal at the same time hat the npn has current flowing into its base from the signal. So each device will conduct a collector/emmitter current given by its base current and its gain. If both devices conduct even partially at the same time then you get shoot through.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
ben123324 wrote ...
....Under what conditions will one npn/pnp leg shoot through? If the input signal is maximum then the npn will conduct and the pnp will not. If the input signal is minimum the the pnp will conduct while the npn doesn't...
... If both devices conduct even partially at the same time then you get shoot through.
yes this is what i was imagining youd meant, ok, the schmidt trigger is only meant to clean up analog slop, and not essential if driven carefully. im thinking that a BASIC stamp should be good enough then... let me look at the datasheet.
i see the BASIC stamp (mine) can output 20ma source or sink safely, and ill half that just to be sure.
EDIT: ill use 6 transistors total, 2 PNP and 1 NPN on the left, and 2 PNP and 1 NPN on the right, thus illbe able to source or sink 200mA, despite the PNP's lack of current handling... BC547 (NPN) and BC556 (PNP)
Registered Member #3900
Joined: Thu May 19 2011, 08:28PM
Location:
Posts: 600
Yup, exactly. And you don't even need a Schmidt trigger to do that. Any logic device will work. I think that th designer of that circuit has some application where there's jitter to clean up on the inputs.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
ok ill try this one... without the schmidt gates...
click on it and it wont be too dark. im thinking 5 volts is the maximum i can safley power it by. Since ill be elevating the stamp pin and gate node of the PNPs...
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.
need a small H bridge for motor.
