how to heat a small box

$c$ is the specific heat of the material in question (~1.005kJ/kgK for air at room temperature) and $\Delta T$ is the temperature change.A 5x5x5 cm box will have an air mass of ~0.15 g (air density ~1.2 kg/m$^3$).For a 1W (1 J/s) heater this gives a temperature change of The resistors are on top of a small PCB so are insualted to some degree from the box, but I will elevate them slightly as you suggest, therefore limiting conduction losses.

Now it's time to cook some parts. Featured on Meta Stand the heater on one side a couple of inches from the sides of the box. Do what you can to keep the garage from getting to cold. Can I make anything from stuff at home to heat up this area? However for temperatures near room temp.

So using Ohms Law (V/R) 5V / 25 Ohms = 200mA, Watts can be calculated from this by simply multiplying V * A therefore 5V * 200mA = 1WWith a 10cm x 10cm x 10cm box, it goes down to ~1 K/s.Hi Nivag, thanks you very much for the response and calculation. Intuitively I would think the transfer of heat from the air to the box would be slow compared to the heating of the air. They won't be used here, but you never know what you might need them for, like the edges of mats you actually put on the floor.Almost done.

I am looking for any guidance and calculations that will save me time instead of having to make different boxes and learn by trial and error.A simple approach would be to just consider the heat added.The specific heat equation gives the temperature change due to heating as$$Q=mc\Delta T$$ where $Q$ is heat added, $m$ is mass. P.S. Fast, Cheap, and Easy Hot Box: Since it's been in the 40's lately, which means my garage is in the 60's, it's been taking forever for paint to dry on parts before I hydro dip them, so I needed an insulated box to heat up the parts and get them to dry. Start here for a quick overview of the site Input 1 Watt electrical say (eg 5V 200 mA ) and it will end up as heat one way or other. The whole concept of 'dumbing it down' to get something functional instead of spending inordinate time and money is great!I love using the Anti-fatigue mats for the box - classic! @Ant The 8 times smaller box will heat 8 times faster, but 6.6/8=~1. My raised wet finger waved in the air (as it were) assessment says that 1 Watt is very small compared to losses liable to be encountered.

I would expect these loses to be low. 1) Heat losses from the box. Where is the temperature probe located?

All in all, I am pleased with the results. 2) Heating the box. Insulate the outside of the grow box so it retains as much heat as possible when the lights are out. About: I'm just a lowly professional maker (wait, you're gonna PAY me to come up with weird stuff and then build it?!?) Second he didn't mount the bulbs in the lid. Run the cord either out the top or through an edge somewhere, whichever works best for you. The temperature probe will probably be near the top, offset to the side slightly, so it's not directly above the heating element. almost better - if fan was entirely internal then you need no heater - power the fan at the level required. I picked all 3. Run your lights during the coolest part of the day for free heat. But if this effect is minimal, then a simplified approximate solution is preferable as some design parameters may change slightly. Instead, he uses those light fixtures with a parabolic dish and squeeze clamps and just clamps them to the form when he puts a bow in the oven. Most of the mats I've seen have strips along 2 edges that leave a more finished edge. Chances are you'll have to play with it to get the temperature you want, but once it's set it doesn't vary much.

Fabulous Instructable! my setup, in a 65° garage, runs for about 20 seconds every 3-4 minutes at 150°. @sara, for the heater i simply used 4 * 100 Ohm resistors in parallel, this equates to 25 ohms.

I don't know if it works any better, but it keeps me from worrying about melted parts. Any suggestions? I need to try and equate this to actual time now, but can use your calculation on the previous 10*10*10 example I agree with the heat loss being minimal through the box as it's wood. The roots love to be warm and this will help …

I will wait to see what other answers come from the community and pending repsonses will accept this as an answer.Hi Am304. Use a 120Vac thermostat heater with a constant fan INSIDE your closed freezer set to 85'F or use a Honeywell thermostat rated for 120Vac with your hair dryer and wire up the heater but keep the internal fan circulating for homogenous air temp. Electric heaters typically have electronics and relays or bimetal contact points that all create an arc when breaking the connection. Inevitably if you heat the air in the box this will transfer to the box itself.

It only takes a minute to sign up.I am not after exact timings - I am aware that losses through the box will have an effect. A friend of mine made his heat box out of foam board insulation, but he had some variations. The Overflow Blog Unless your box is well insulated it will lose heat via radiation and conduction.