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 #902
Joined: Sun Jul 15 2007, 08:17PM
Location: North Texas
Posts: 1040
ok, for my ROV I am using a membrane keypad as the primary input device, as they are watertight it is a 25 key pad, with four columns and five floating buttons on the bottom I deduced that the five floating buttons were really another column just misplaced, making a standard 5x5 matrix
The Schematic is Attached.
The connectors on the far left are for my Elexol USB I/O 24 module, which has 24 I/O ports and uses three sets of ten pins (two in each set are for power and ground). The connector arrangement fits using 20 pin ribbon wire, so there is a 20 pin and a ten pin to get all of the connections over and save space and connectors
the I/O board (for the matrix connections) are configured watch for being turned HIGH. the pins 8, 7, 9, 12, and 14 (group one) are normally HIGH due to the connection, via resistor, to the 5V source. The pins 2, 3, 4, 5, and 6 (group two) are normally LOW and are connected to ground via a diode (to prevent one pin from activating upon another's signal) and a resistor, R6. The resistor R6 is of relatively high value. This simply prevents the pins from floating, and therefore helps stop false signals.
When a button is pressed, it allows the corresponding transistor, which is connected to a group from pin one, to conduct and therefore the amount of current flowing through the resistor to said pin of group one will not be enough for the pin to be read as HIGH, so the software will notice it has become LOW. As the current passes through the button, it goes to the corresponding pin in group two and makes it read as HIGH. The reason that R6 has a relative high value is because I want more of the current flowing through the pin on the module, rather than strait to ground.
I have made a similar circuit in the past, but that one used a ten transistor array and I want to drop the part count and complexity. Plus, I never thoroughly tested that circuit.
Does anyone see any problems I might encounter with this? This will be a mess to prototype before making the final PCB, and before I get the transistors and decimate my small supply of rainbow ribbon wire I want to make sure it is all ok.
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.
Membrane Keypad Matrix Circuit - how can I improve it?
