HALE Heater components
Eric
Brian was concerned about the heaters (battery powered) getting too
hot and eating through the payload box.
In our experience this has never happened. However, we typically mount
the heaters on a small piece of balsa wood, which effectively
insulates the box from the heaters. We have crammed the NXT, wires,
ect right up agains the heaters without any ill effects to those
components.
REMEMBER: the heater works via radiation, not conduction or convection
because there is no air. Thus, you want to position the heater in such
a way that it has direct line of sight to the component(s) you are
trying to keep warm.
Eric
David Levy - Coach
I have a team member working with his parent on the heating unit.
They are going to try the reed-relay solution that you provided. Is
it just a matter of cutting one end of the NXT cable and connecting
the two of the wires?
Thanks
David Levy
FLL Team 90 Coach
Davis, Brian L.
> They are going to try the reed-relay solution that you provided.
Sidelight: I'm also trying to implement the reed relay control, but using the HT Protoboard to activate it. Initial experiments show it can deliver enough current to activate it, but I'll have to see how the entire system loads out (other sensors on the protoboard, and the NXT, will potentially reduce the current).
> Is it just a matter of cutting one end of the NXT cable and
> connecting the two of the wires?
Disclaimer: I've not done this. But I think you just need to use the two wires that will provide a 9V connection (in other words, *not* the I2C wires). To make the process easier, I might do out and order some of the very flexible wires from Mindsensors. These are non-standard, somewhat more delicate... but easier to cut up I think, and lighter in a mission like this (at least that's why I got some).
Eric also wrote:
> Brian was concerned about the heaters (battery powered) getting too
> hot and eating through the payload box. In our experience this has
> never happened.
OK, so that small piece of wood is good enough. Good to know. I'm thinking of running the NXT with the back cover off, and the heater snuggled near it to provide as direct a radiant source as possible. The camera batteries are more of a problem, however. In retrospect, hacking the battery connection in the camera so the camera batteries are external, and "snuggled up" against the NXT batteries, makes the best thermal sense I guess.
> We have crammed the NXT, wires, ect. right up agains the heaters
> without any ill effects to those components.
Excellent - just what I wanted to know. Thanks!
> REMEMBER: the heater works via radiation, not conduction or convection
> because there is no air. Thus, you want to position the heater in such
> a way that it has direct line of sight to the component(s) you are
> trying to keep warm.
Have you ever tried conduction, i.e., a small piece of metal to serves as a "heat pipe"? I think I may have to split my two heater resistors for best coverage in the payload (toward the NXT, one toward the camera).
--
Brian Davis
Eric
intervalometer) to clarify how to connect an NXT wire to the reed
relay. Hope this helps.
Eric
On Jun 9, 7:31 pm, David Levy - Coach <david.l...@restonrobotics.org>
wrote:
Eric
that is a REALLY good idea that we'll keep in mind for now on.
Brian Davis
> hindsight that is a REALLY good idea that we'll keep in mind
> for now on.
this mission we'll see just how well it does work. I'm not sure I'm
going to bother putting a metal cage around them, but I'm planning
gluing a LEGO beam to the back of the wood (basswood)... thoughts on
if the temperature will get too high (I know, test it, but I thought
I'd ask first).
On a related heater issue, you mention different battery set-ups. A
square 9V that seems to heat to a high temperature but not long (45
minutes), while 4 AA's on a continuous feed supply 2/3rds the heat but
for 2 hours. You also mention that if you can control it, you can use
AAA's. How many, and how long does that last? Or in other words, if I
can control the heaters (via the HT Protoboard), what set-up would you
suggest for the lightest weight? Is there a suggested minimum
temperature to aim at?
--
Brian Davis