DIY substrate heating completed

[justDIY]

has anyone diy'd a substrate heating system?

I've read articles on the Krib and by G. Booth, but they fail to go into specifics, like what kind of wire exactly, and how big a transformer exactly

I imagine that's because of safety ... but livinging dangerously, has anyone done it themselves?

I'd like to setup a coil ssytem for my 30 gallon which will be rebuilt soon.

 

[loganj]

Never done it...a few uneducated thoughts to speed you on your way to electrocution though 8O . I have installed a few heat tape systems for reptile breeding racks. I wonder how well the reptile heat tape would work on the bottom of the tank? It uses 120v so it might not be a good idea. Not sure how you'd control the temp either. Maybe one of the aquatic temp controllers could be used with it? Not sure. Something to look into maybe. Perhaps you could use an insulated cable of similar resistance to reduce the risk?

 

[justDIY]

the system I'd like to build would use low voltage (12 or 24v) to make things safe for me and my fishies..

of course, i'd use insulated wire

looks like I got more reading to do, maybe some experimentation

 

[justDIY]

ok, the articles that involve diy substrate heating have math in 'em... Not being a big fan of math, and with the limited resources available, here's what I've come up with;

I have a 50 watt 12 volt transformer that once powered a low-voltage halogen light.

I have approximately 12 feet of 30 gauge copper/tin insultated wire woven in a snake-like pattern on some craft canvas.

I have a 10 gallon aquarium, filled with 2 gal of water for testing

The canvas is about 1/4" from the bottom glass suspended by some rocks

When I connect the wire to the transformer, the small amount of 30 ga wire that is out of the water gets warm, but the coils under the waters I cannot feel any temperature difference.

I assume that I must have too much resistance / too long of wire, and that is why it's not getting hot, or is my voltage too low? I first tried 5 and 9 volts, and the exposed wire didn't even get warm with them.

Should it get warm enough that you can feel it, or doesn't it work that way?

If I remember high school circuits class correctly, would running another 'snake' of wire near the first one, and wire them in parallel to the transformer, this should cut the resistance in half, which should generate more heat?

 

[justDIY]

chalk another one up for DIY!

In 20 min, my substrate heater raised 2 gallons of water 3 degrees above room temperature

The problem I had was not enough wire ... 12 feet wasn't enough resistance, so it blew the fuse in the transformer.

Having upgraded the fuse a few amps (still within safe limits), and increasing wire length to around 20 feet, the system now works.

I also redesigned the 'support' after considering what would happen when plant roots grew into the plastic craft canvas.

the new support consists of 3x 1/2 cpvc tubes configured in a 3 bar "ring", which the 20 feet of wire is wound around each 'bar'

connections were made with solder to the supply leads, and covered with silicone caulk and heat-shrink tubing.

I'll post some pictures as soon as I finish a roll and have it developed.

 

[loganj]

glmclell, you're a DIY maniac! I love it. Great job and I'll look forward to the pics.

 

[justDIY]

well, more research showed that intermittent heating would provide better "water flow" through the substrate, from heating and cooling ...

so I've setup the heater with a timer that runs it for 1/2 hour periods, with a 1 hour "cool down" inbetween

the timer has also helped reduce the tank temp a bit, seems to be holding at 78 now.

if I were to repeat this project on a larger scale, I'd want to research some sort of temperature control circuit (rather than buy a controller) that will regulate the heater more precisely

now the real tests will be:

will my plants notice or care that they now have "warm feet"

will my solder connections hold up under water for an extended period of time

 

[RogerMcAllen]

More resistance= More heat

Superconducting wires generate no heat because they have no resistance.

 

[justDIY]

hmm ... actually, I've found it to be more resistance = less heat, given that I'm using a fixed amount of wattage

Increased resistance in the wire makes it have a higher voltage drop, and results in the lower amount of voltage that is there not being able to push as many amps, resulting in a lower current.

The 12 ft wire actually got hot to the touch (and was trying to draw over 100 watts from a 50 watt transformer), before it blew the fuse that is. The 20 some feet (only draws around 43 watts) doesn't grow warm at all (that I could tell just touching it underwater).

Before I setup a filter to circulate water, touching the glass near the bottom and moving upward you could feel the difference, a neat temperature gradient had developed in the water ... now with a filter circulating everything, it's all the same now, except for under the gravel, which is still a bit warmer.