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 #72
Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659
Let's get quantative here please. How fast, in degrees C per second, must the hot plate slew from -20C to +100C? Without that spec, this thread just becomes a game of " Why don't you, yes but ..."
BTW, is the payload in good thermal contact with the plate? If it is a thin film on the plate then you will be OK, but if it is significantly extended in the z direction, then even an infintely steep temperature step on the plate may not heat it through fast emough?
With a slew rate, and an estimate of minimum mass for the top plate and the chemical payload, you can then arrive at an input power. If you want a lot of power, then energy storage is suggested.
I would guess that over-heating the reaction is not wanted, in which case methods that heat to a specific temperature would be good. Dumping a known amount of energy from a capacitor bank into a known mass of heater and payload will produce a repeatable temperature rise. Flowing steam through a thin-walled box will not exceed 100C, and can store a lot of energy
Do you have an already defined geometry for the reaction, and you must fit a temperature control system to that, or can you start from scratch and build your reactor round your heater? I'm thinking deposit the chemicals as a thin film on some stainless steel or nichrome wire. Clamp the wire between two electrodes cooled to -20C. Pulse some caps into the wire to raise it to 100C in the RC time of your caps and wire resistance. The centre of the wire will heat adiabatically, the ends will be conduction cooled. Continue to flow a lower current to maintain the wire at 100C if it must dwell at that temperature for more than a moment.
Or instead of a wire use flat strip to beat into a crucible, it'll just need rather more energy and current to heat.
Are you using glass for its chemical nature, or because you want to do transmission microscopy? If you can use a metal substrate, then it's much easier to heat.
Registered Member #1025
Joined: Sun Sept 23 2007, 07:53PM
Location: Czech Rep.
Posts: 566
NeilThomas wrote ...
Let's get quantative here please. How fast, in degrees C per second, must the hot plate slew from -20C to +100C? Without that spec, this thread just becomes a game of " Why don't you, yes but ..."
The point is how faster so better...At the moment it takes aprox. 10secs using the peltier on full-trotle. My aim is to shorten the time at least twice...
NeilThomas wrote ...
BTW, is the payload in good thermal contact with the plate? If it is a thin film on the plate then you will be OK, but if it is significantly extended in the z direction, then even an infintely steep temperature step on the plate may not heat it through fast emough?
I've just noticed I made a stupid error in the scheme. Of course the heater module (the metal plate or better the resistive heater) must be above the Peltier and not below (like it is now) - It would make no sense to heat the glass through the peltier... The contact between the glass and the heater is very critical - I'm using drop of ethanol as a heat conductor. Ethanol has two main advantages - it never freeze when I'm cooling it down and also tells me when the right temp is achieved during heating because is starts to boil around 90C. It simply protects the sample from overheating
NeilThomas wrote ...
With a slew rate, and an estimate of minimum mass for the top plate and the chemical payload, you can then arrive at an input power. If you want a lot of power, then energy storage is suggested.
I would guess that over-heating the reaction is not wanted, in which case methods that heat to a specific temperature would be good. Dumping a known amount of energy from a capacitor bank into a known mass of heater and payload will produce a repeatable temperature rise.
This is exactly what I'm going to try now. I decided to make a flat spiral from normal stainless steel wire and try to discharge a big cap or lead-acid accu through it. Need to solve some kind of heat resistant resin to make a nice flat coin like stucture from the spiral to achieve maximum contact with the glass.
NeilThomas wrote ...
Are you using glass for its chemical nature, or because you want to do transmission microscopy? If you can use a metal substrate, then it's much easier to heat.
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.
Fast temperature switching using Pletier and Induction heater
