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View Full Version : dimmer/on off t'stat in series for more precise control of heat tape? help!

ross2k
12-08-02, 04:52 PM
Hi guys,

First of all here's a pic of my rack which was messy then and its still fairly messy.

http://www.levineantiquelighting.com/ross/ross'%20rack.JPG

Hope that works. Anyway you can't see it in the picture but I'm using a slide dimmer to control the 8 feet of 4" heat tape. It goes under the 12q tubs. I have 1 BRB living in there right now, and she's still not eating very consistently. In the two months I've had her she's eaten 3 times. I thought the problem was originally the temps were too high, I lowered the temps and she did take from the tongs (YEAH!). But then the next week there was no interested in food, and again the next week. Now once again the temps are off. I check the warm and cool side several times a day with my temp gun. I don't think the problem is humidty because I spray down all the paper towels and the whole tub inside also several times a day, its usually up around 85-90%. A few days ago I temped late at night and noticed that the temps were low, about 69 on the cool end and only 74 on the warm side. I decided to turn the dimmer up a little. Then yesterday during the day I temped and it was too high! It was 87 on the warm side and 73 on the cool side. She was on the warm side still, a bit strange.

So heres what I'm thinking. I realize that probably my best bet in this situation is to look long term and just buy a digital proportional thermostat (im thinking big apple herp) but I don't have the cash at the moment. I'll probably buy one by february. But right now I do have an on off thermostat (Alife) which I could use in series with this dimmer which I could probably get more accuratly consistent temps. I was thinking if I raised the temp on the slide dimmer and had the thermostat as a shut off so that once the heat tape hits 92-93 (85 in the tub) then it'd shut off. This way there would be a bigger gap between times that the heat tape will be on during the day to keep the temps a little lower, and at night the thermostat will just stay on longer to maintain closer to low 80s. The problem then is that 24/7 I'll still have fluctuations.

Does this seem like a worthwhile idea, or am I just chasing a pipe dream here? Perhaps what I'm going after shouldn't be acheived. After all, in the wild it cools at night too.

Any thoughts?
sSNAKESs.com
12-09-02, 05:17 AM
if you use a thermostat your temps will stay within a few degree's 24/7... I keep all my snakes at the same temps 24 / 7... if it wants to cool off they just go to the cool end :P a thermostat is a must... dimmers are completely unreliable. IMO
escm
12-14-02, 05:42 PM
Yup I agree with Jeff , I don't know how people keep track of temps without a thermostat...however I do also like my dimmer. I have a red bulb on a dimmer that stays on a constant low setting and provides the overall ambient temps I like.

Hey Jeff,

Could you (or do you) have your lamps hooked to a digital thermostat? Would they dim up and down a lot and hence confuse the snakes photo period? Or do they stay a pretty constant intensity?
ross2k
12-14-02, 06:03 PM
No lamps in that room. Only a window. Its also my bedroom so occasionally I turn the lights on in there. I suppose that could be stressing her out.

I've tried something a little different. I had a spair 150w ceramic heat emitter and dome for it. I hooked it up to the on off thermostat and just hung it in that room. I've got the t'stat set to 72 degrees. The room is small, and I'm still working on sealing/insulating it a little bit better but hopefully with this contraption I can at least keep the temps from going below 70 in that room. Which should mean no dips in temp inside her tub due to the ambient drop.

This has worked so far in the past few days. I've seen the temps in the room go from 69-74. The temps in her tub have been perfect. low 80s on the warm side, and low 70s on the cool side. I offered her a thawed hopper from the tongs about 15 minutes ago. She shows a lot of interest, moves around to check it out, LOTS of tongue flicking. But then she loses interest and either starts checking out the hemostats, or playing around, or just going back to her hide.

I'm thinking conditions are fine, she's just a poor eating individual.
Tim_Cranwill
12-14-02, 06:09 PM
Just a question about dimmers. Wouldn't it be possible to calibrate the dimmer? I don't use any at the moment, but I've thought about it. It's nice to get some experienced opinions first.
escm
12-14-02, 06:29 PM
You mean like enscribe on the dimmer itself a temp. guage?
Matt
12-14-02, 08:24 PM
if you use a thermostat your temps will stay within a few degree's 24/7... I keep all my snakes at the same temps 24 / 7... if it wants to cool off they just go to the cool end :P a thermostat is a must... dimmers are completely unreliable. IMO


Jeff.....what kind of thermostat do you use?
thx
Tim_Cranwill
12-14-02, 11:37 PM
Yeah, I mean like set it to 1/2 leave it for a bit record the temp and then do it at 3/4 and repeat, 1/4 repeat. Seems like it should work to me, but I might not know how dimmers are designed and such.....
ross2k
12-14-02, 11:48 PM
Thats exactly how it works with dimmers. Thats also why the slide style of dimmer are superior to the rotary variety. I suppose either way it's easy to just mark exactly where you want it.

The problem as I was addressing earlier in this thread is that the dimmer is blind to the ambient temp in the room. So supposing you did the process of calibration, or really just identification. You set the dimmer to be perfect for the heater in your enclosure. Lets say you did that at 3 in the afternoon when it was 75 degrees in the room. Well what happens at 3 AM when the temp is 65 degrees in the room? The dimmer doesn't compensate for this change, and thus the temps in the enclosure will be too low.

The answer for me (for now) is to try to insulate my the room and heat the room with a thermostatically controlled heater so as to keep the temps in the room above 70 degrees and "calibrate" the dimmer presuming that it will always be 70 degrees.

The better solution (what I intend to do) is digital proportional thermostats. No more screwing around with low quality thermostats or dimmers, enough is enough.
Tim_Cranwill
12-15-02, 12:51 AM
Gotcha. You're right.
Lisa
12-15-02, 02:04 AM
Originally posted by cranwill
Yeah, I mean like set it to 1/2 leave it for a bit record the temp and then do it at 3/4 and repeat, 1/4 repeat. Seems like it should work to me, but I might not know how dimmers are designed and such.....

Thats basicly what we've been doing with the rheostat kate made. unfortunetly we also have the problem of the neighbours downstairs liking their heat at insane temps and trying to cook us. oh well, it lowers our bill
ross2k
12-15-02, 03:42 AM
You know what lowers your bill even more? Thermostats. If your heater is controled by something that realizes that its going to require less energy to meet the need, then less energy is used. Although a dimmer saves energy over using the device at full throttle, it will still use a constant level of energy. The thermostat just wont turn on at all or will require a smaller level of juice to satisfy the temp.

Boring details I'm sure, but if you live in CA then PG&E is a big deal. Of course, the amount of heat tape I'm using couldn't reach a kilowatt/hour if it tried in a month...