Author Topic: Could I make a simple tiny heater with 1/2 watt resistors? (Read 17330 times)

Jay112 · « **on:** December 19, 2015, 12:48:59 pm »

I have a CCTV dome camera that gets too cold in the winter time and produces blurry images until the temperature warms up. My idea is to put a tiny heater inside the dome. The dome is about the size of a human fist. I might only need to raise it a few degrees Fahrenheit for it to have a much longer working period during the day.

The camera is powered with 12 volts, and I think there are an extra 500mA on the power supply that's feeding it (I could replace it with a different supply if necessary).

I have a box of 1/2 watt resistors, ranging from 10 Ohms up to 1M Ohms. Is there any way I could use a few of these to try to raise the temperature of the dome by a few degrees?

I've seen many google results for "use resistor as heater", but the top results seemed to be about very specific situations, so that's why I was interested in hearing your advice here. Thanks!

Gyro · « **Reply #1 on:** December 19, 2015, 01:22:56 pm »

Certainly you can. The cabinet heaters available for larger cabinets are basically just power resistors in a convenient enclosure.

The dissipation you need may well be smaller than you think - a little experimentation is needed to achieve the desired result without overheating it in the summer.

You may find that a pysically larger resistor (such as 1 or 2W) under-run at 0.5W or less is more friendly due to lower surface temperature.

Jay112 · « **Reply #2 on:** December 19, 2015, 01:29:14 pm »

Thanks! I'll actually be removing the heater in the summer.

I recently saved the PCB from a broken coffee maker. It has very large resistors on it, seeming physically 4 times larger than my 1/2 watt resistors. I haven't tested the Ohms yet though. Do you think some of those might make good stable heaters?

Gyro · « **Reply #3 on:** December 19, 2015, 01:41:48 pm »

Potentially, depending on their values and the space you have available. Remember that a resistor of the same resistance value will always dissipate the same power (heat) for a given voltage and current, it's just that larger the resistor package will do so at a lower surface temperature due to its larger surface area.

Kleinstein · « **Reply #4 on:** December 19, 2015, 02:25:32 pm »

You could also use something like 2 or 3 of the smaller resistors. The first part is to estimate how much power is really needed. Allready just a few degrees may be enough to keep humidity low enough and prevent condensation. So I would test it wtih something like 1/8 - 1/4 W or a 560 Ohms to 1 K resistor.

Seekonk · « **Reply #5 on:** December 19, 2015, 04:24:16 pm »

I've seen microprocessors with resistors glued on the top so they would still work at lower temperatures.

Jay112 · « **Reply #6 on:** December 19, 2015, 04:59:03 pm »

Thanks for the info, everyone. So far I'm planning on trying Kleinstein's idea to use 2-3 of the smaller resistors first. I'm going to go on the roof now where the camera is, to see how much room I have to work in there. I'm pretty sure there's a nice flat metal part on the bottom, so I'm guessing I can probably have the resistors rest there. Maybe I'll try to take a few pics to show you guys the situation.

Tom45 · « **Reply #7 on:** December 19, 2015, 05:24:03 pm »

If your 500ma estimate is correct, you have 6 watts available: 12 volts * 0.5 amps.

Power dissipated by a resistor is E² / R , or 144/R

To give a bit of safety margin, lets plan on 4 watts with the power supply you have now.

So that works out to R = 144 / 4 = 36 ohms.

Since you are using 1/2 watt resistors, you will need 8 of them for 4 watts. Using standard values in parallel, you need 8 270 ohm resistors in parallel. Or 8 4.7 ohm resistors in series. Or some other combination of series and parallel that combines to give around 36 ohms.

Jay112 · « **Reply #8 on:** December 19, 2015, 06:06:50 pm »

Thanks Tom! That's very helpful!

I tried to get some more specifics on the current being drawn, but my multimeter kept telling me that the camera was only drawing 5.5mA. That seemed too low to me, so I looked at the camera's datasheet and it said the power consumption is 218mA at 12v.

The strange thing I just learned is that the camera still works if I disconnect it from ground at the power source. I've never seen that before. I wonder if it means there's a mistaken connection to ground somewhere, or if somehow that's normal behavior for CCTV cameras (like maybe they're connected to ground via the video connection?). I did find continuity between the power-supply ground and the center pin of the video cable.

When I go on the roof to open the camera (hopefully soon), I'll probably try to test the current draw from up there, if it's not too difficult.

Also I learned that the power source can supply 500mA (again I could swap that out if necessary). So if we assume that the datasheet is correct that the camera draws on average 218mA, could you guys please help me with the math again for choosing resistors? I was planning on researching how to do the math today, but I'd probably end up making mistakes anyway, so it would be great if I could get some input.

Len · « **Reply #9 on:** December 19, 2015, 06:14:41 pm »

Quote from: Jay112 on December 19, 2015, 06:06:50 pm

The strange thing I just learned is that the camera still works if I disconnect it from ground at the power source. I've never seen that before.

You need to be more diligent with your EEVBlog watching!

https://youtu.be/2yFh7Vv0Paw

Jay112 · « **Reply #10 on:** December 19, 2015, 06:41:25 pm »

Thanks Len! I usually don't watch videos, because I prefer reading. That was the first EEVBlog video I've ever seen. The man has some amazing teaching skills!

Jay112 · « **Reply #11 on:** December 19, 2015, 06:52:39 pm »

It ended up to be too cold and windy outside (20 degrees F), so I decided to put this off until tomorrow, when it's supposed to be in the 40s.

I think my fingers would've been frozen if I tried to do anything out there today. And also I was worried about my multimeter and camera suffering from the temperature changes.

Lycaon · « **Reply #12 on:** December 19, 2015, 10:25:25 pm »

Maybe one of these would work?
https://www.sparkfun.com/products/11289?gclid=CjwKEAiAndSzBRDp5P232v-qtHkSJABw-VdtT2V0BQG4bQ4BGjY4O8pi1kf5l3wlnYvkOFvt9hskwRoCqrjw_wcB

fivefish · « **Reply #13 on:** December 20, 2015, 01:31:11 am »

or a tiny incandescent bulb?

Ian.M · « **Reply #14 on:** December 20, 2015, 03:06:21 am »

A bulb is less reliable and introduces light pollution in the housing. Simply add as many 560R or 470R resistors in parallel across the supply as it takes to prevent condensation. Each dissipates a little over 1/4W.

Jay112 · « **Reply #15 on:** December 20, 2015, 07:49:08 am »

@Lycaon: that looks like a good idea, but I would prefer to try using something I already have on hand first.

Would a regular 120v incandescent candelabra bulb (say a 5 watt version) still produce heat when powered by 12v DC? And if it does, I'm assuming the lifespan would be much longer than usual? I would prefer to not have to introduce 120v AC into the enclosure.

BTW I recently learned that the camera can optionally take 24v AC instead of 12v DC. I already have a 24v AC supply and the switch would be easy, if you think this might allow more heating options.

LukeW · « **Reply #16 on:** December 20, 2015, 10:39:37 am »

If you go with a 24VAC power supply (or whatever you have on hand, closer to the upper end of the camera's allowed voltage input) you may find that the problem solves itself with no other components added, due to increased power dissipation in the camera's own power supply regulators.

Test it... maybe you don't need to do anything!

Gyro · « **Reply #17 on:** December 20, 2015, 10:43:54 am »

Quote from: blueskull on December 20, 2015, 04:12:54 am

I vote for the bulb solution, painted completely in black, or covered by black tin foil.

It gives much larger surface area to evenly radiate heat to the entire housing, rather than just some hot spots as if implemented with resistors.

How's a bulb going to be better than a few resistors running well within their dissipation ratings. You've got all the hassle of masking the bulb from All visible light, realizing you've picked the wrong wattage and doing it again, ANY light leak that develops (paint flake) is going to be a major problem. Arranging a holder (or directly soldering to the bulb). Just doesn't seem as practical a solution.

The OP started off by talking about a "small dome" and 1/2W resistors, these solutions seem to be getting bigger!

Edit: +1 for trying the higher supply voltage, the camera is probaby (hopefully) using a linear reg.

Lee Leduc · « **Reply #18 on:** December 20, 2015, 04:19:20 pm »

Here's a link for a simple resistor heater to keep a telescope from fogging up. I made one years ago and it worked great. I added a simple PWM circuit to adjust the temperature.
http://www.skyandtelescope.com/astronomy-equipment/diy-dew-heater/

Jay112 · « **Reply #19 on:** December 20, 2015, 05:25:48 pm »

I finally got some pictures. It's dangerously windy today (gusts up to 35MPH), so I probably won't be able to do any precision work up there today.

I think there looks like room for a resistor heater on the "floor" on the side that doesn't have any wiring (the top of the 2nd picture). There's definitely no room for a lightbulb anywhere.

@LukeW and Gyro: I would love to do your idea first of trying the 24VAC power supply and seeing if that fixes the problem, but the problem is that if I see that it doesn't work, then already it will have become too cold for me to try out other ideas. So I think I'll try a small low-power resistor first, and then if that doesn't work then I can try with the 24VAC idea. It's supposed to be warm all week, so for an entire week I probably won't be able to see if I fixed the problem (it only shows up when it's below 20F).

@Lee Leduc: That's a great link! Thanks!

I'll probably make the resistor-heater easily removable, but I have a question: Is there a way to make the heater be able to handle both 12VDC and 24VAC?

Jay112 · « **Reply #20 on:** December 20, 2015, 05:34:20 pm »

That DC fan on the left side of the lower picture was custom-installed by me. I was having problems with it overheating in the summer time, but when I installed that fan it fixed the problem.

Last winter I kept the fan unplugged. I can choose to keep it plugged or unplugged this winter. An interesting thing would be to have the resistor heater behind the fan, so that it cools down the resistors and blows the heat towards the PCB. But I think it would be way easier to just have the heater sitting on the floor of the unit.

Jay112 · « **Reply #21 on:** December 20, 2015, 06:41:44 pm »

I just tested the current draw at the camera end, and it was only 3.9 mA. Does that make sense to anybody? Doesn't it seem very low?

I just made a heater according to the directions at Lee Leduc's link (http://www.skyandtelescope.com/astronomy-equipment/diy-dew-heater/), only I used 6 22 Ohm resistors. At 12 volts it should produce about 1.1 watts. I think I might try to go up there soon and see if it fits well in the dome. I'll take a picture if everything ends up fitting.

Gyro · « **Reply #22 on:** December 20, 2015, 07:31:34 pm »

I think you must have got your resistor values wrong. 4mA would imply a total of 3k, so 500R per resistor... assuming you've strapped it to 12V. Time to double check your values.

With regard to placement of the resistors. As you've got a fan in there the logical place would be to string them in front of it, that way air will blow over them and the warm air will circulate. No danger of hotspots and probably more effective too.

It looks as if you have unused mounting holes on the fan that you can use too.

It's possible that just running the fan would be sufficient to keep things clear but I'm sure the electronics and mechanics would appreciate a bit of warmth in winter too.

Jay112 · « **Reply #23 on:** December 20, 2015, 07:39:19 pm »

Quote from: Gyro on December 20, 2015, 07:31:34 pm

I think you must have got your resistor values wrong. 4mA would imply a total of 3k, so 500R per resistor... assuming you've strapped it to 12V. Time to double check your values.

With regard to placement of the resistors. As you've got a fan in there the logical place would be to string them in front of it, that way air will blow over them and the warm air will circulate. No danger of hotspots and probably more effective too. It looks as if you have unused mounting holes on the fan that you can use too.

It's possible that just running the fan would be sufficient to keep things clear but I'm sure the electronics and mechanics would appreciate a bit of warmth in winter too.

I'm sorry I didn't write clearly enough. I meant that when I didn't even have the heater connected, the camera alone was drawing only 4mA. That seemed low to me. I'll go test it now that I have the heater connected.

This is where I placed the heater. Looks like a pretty good fit, huh? Although in the picture it looks like the top row might be touching the bottom, they're not actually touching, and there's about 1/4" of space between them.

My biggest question is: What would happen if I ran 24VAC through those resistors?

I unplugged the fan for now, because if I end up switching to 24VAC, then I don't have to worry about blowing out the fan.

Jay112 · « **Reply #24 on:** December 20, 2015, 07:40:55 pm »

Also: I tested the voltage at the camera end, and it's at 12.02 volts.

Jay112 · « **Reply #25 on:** December 20, 2015, 08:08:37 pm »

I apologize about the low milliamps thing. Most likely I was just reading my (new) multimeter wrong. I had given my old multimeter to a friend just a few days ago, and if I still had that one I would've been able to see the discrepancy.

Now I'm getting 330mA, tested with 2 different meters. That makes sense for a camera and the new heater I installed, right? I'm too tired to go back up on the roof today, otherwise I would test it with and without the heater. Maybe I'll do that another day.

Gyro · « **Reply #26 on:** December 20, 2015, 08:14:42 pm »

Simple answer first, the same resistors at 24V will dissipate four times the power... 4W rather than 1W, you'll be over-running your 1/2W resistors.

I suppose it's possible that a small CMOS camera might consume so little current, I would have expected a bit more considering it's driving 75R video. Maybe not.

I'd still be tempted to put the resistors in the airflow so that they're acting directly on the dome rather than losing heat into the lower casing.

P.S. Just seen your note on the current, yes that seems more reasonable. Sounds like time to take a break for the day then

Jay112 · « **Reply #27 on:** December 20, 2015, 08:28:32 pm »

Thanks for the info, Gyro!

About the fan: When it's 0 degrees outside and the fan is blowing, do you think maybe the end result will be that it dissipates most of the heat from the PCB, whereas if the fan wasn't on there might be a warmer area where the PCB is generating heat?

About the wattage: if my heater is currently drawing 1 watt (I think it's actually 1.1), and I have 6 resistors, that would mean that each resistor is carrying 1/6 of a watt, right? So then with 24VAC, since it will dissipate 4 times the power, that would mean that each resistor is carrying 4/6 (or 2/3) of a watt, which is over the 1/2 watt rating, right? So then if I simply added 3 of the same resistors to the series, then each resistor should be carrying 4/9 of a watt, which should be safe? Is that correct?

BTW I would definitely consider moving the heater in front of the fan like you suggested, but if I'm going to be switching between 12 and 24 volts depending on the outside temperature, then I can't be having the fan plugged in because I won't be able to go up there on the cold days to unplug it.

Jay112 · « **Reply #28 on:** December 20, 2015, 08:47:25 pm »

Ugh, now I'm certain I did the math wrong, since by adding resistors the resistance and the wattage go up too.

Paul Moir · « **Reply #29 on:** December 20, 2015, 08:57:46 pm »

R = 9 * 22 ohms = 198 ohms
V = 24 (Volts AC RMS, so 24 volts DC equivalent power)
P = V^2 / R, so P = 24*24 / 198 = 2.91W

2.91W / 9 resistors = 0.323W per resistor.

Jay112 · « **Reply #30 on:** December 20, 2015, 09:05:03 pm »

Quote from: Paul Moir on December 20, 2015, 08:57:46 pm

R = 9 * 22 ohms = 198 ohms
V = 24 (Volts AC RMS, so 24 volts DC equivalent power)
P = V^2 / R, so P = 24*24 / 198 = 2.91W

2.91W / 9 resistors = 0.323W per resistor.

Thanks Paul!

I'm thinking maybe 8 of these resistors would be better, because then my wattage is higher when I'm running it on 12v DC. And it looks like if I used 7 it would be too much wattage when switching to 24v.

R = 8 * 22 ohms = 176 ohms
V = 24 (Volts AC RMS, so 24 volts DC equivalent power)
P = V^2 / R, so P = 24*24 / 176 = 3.27W

3.27W / 8 resistors = 0.41W per resistor.
----------------
R = 7 * 22 ohms = 154 ohms
V = 24 (Volts AC RMS, so 24 volts DC equivalent power)
P = V^2 / R, so P = 24*24 / 154 = 3.74W

3.74W / 7 resistors = 0.53W per resistor.

Paul Moir · « **Reply #31 on:** December 20, 2015, 09:27:03 pm »

Hey, no problem at all.

But now you have to put your engineer hat on and tolerance & derate. Those are 22 ohm resistors but they're +- 5% tolerance so they could all be 20.9 ohms. And that 24VAC is probably +- 10% or more. I've seen 28VAC on 24VAC doorbell transformers. So with 8 resistors:
8 * 20.9 = 167.2 ohms
V = 28
P = 28*28/167 = 4.7W

4.7 / 8 is too much. And going with the somewhat lazy but easy derate of 80% of maximum, you're not going to want to use the resistors at more than .5W * 80% = 0.4W each.

(This is just a little pedantic, since you could just measure things and make sure they're OK. I'm just illustrating the point.)

Jay112 · « **Reply #32 on:** December 20, 2015, 09:30:34 pm »

I want to thank everyone for the help! This forum is amazing!

I went on the roof (for the FINAL time today!) and installed the last 2 resistors, so now the heating element has 8 resistors total.

The best part of it is that I can easily switch between .82 watts and 3.27 watts, simply by switching the (indoors) power supply from 12vdc to 24vac. So the solution was more robust than I would've ever thought.

Edit (now that I see Paul's new post): I can't believe I forgot to test the resistance over the heating element while I was up there! It would've been so easy! One thing I did test was the current drawn, and it was 57mA at 12v. I think that's a little lower than I would've expected.

I'm curious though: If I'm only using 24v on the coldest days (definitely less than 20 degrees F), would that coldness help the resistors be able to handle more power without burning out?

Jay112 · « **Reply #33 on:** December 20, 2015, 09:38:24 pm »

Sorry for my beginner stuff, but according to Ohm's Law, if I was measuring 57mA at the heating element, that would mean the resistance should be 210 Ohms at 12v, right? But I used 8 x 22 Ohm resistors, which should've technically equaled 176 Ohms. With something like that, is it safe to assume that the resistors were just off? I think that would be more than the 5% tolerance limit.

I should've double-checked the voltage at the heating element while I was up there too, since obviously that might've thrown off the results.

Gyro · « **Reply #34 on:** December 20, 2015, 09:45:21 pm »

Yes I would think that the resistors are just a little off - they are carbon film ones so their temperature coefficient is pretty high.

Edit: Your supply at the end of the cable is bound to have dropped a little with the additional load, making the resistance 'appear' higher (plus the voltage drop across the current range of your meter).

The low temperature will certainly help their dissipation limit, this is based on maximum temperature before the element and case material (lacquer) degrade, so they de-rate with higher ambient temperature. Forced airflow (your fan) improves this even further against natural convection.

P.S. Sorry, I keep forgetting that you're turning the fan off at 24V

Jay112 · « **Reply #35 on:** December 20, 2015, 10:04:39 pm »

Quote from: Gyro on December 20, 2015, 09:45:21 pm

Yes I would think that the resistors are just a little off - they are carbon film ones so their temperature coefficient is pretty high.

Edit: Your supply at the end of the cable is bound to have dropped a little with the additional load, making the resistance 'appear' higher (plus the voltage drop across the current range of your meter).

The low temperature will certainly help their dissipation limit, this is based on maximum temperature before the element and case material (lacquer) degrade, so they de-rate with higher ambient temperature. Forced airflow (your fan) improves this even further against natural convection.

P.S. Sorry, I keep forgetting that you're turning the fan off at 24V

Thanks for the info!

If you can figure out a way that I can have a 12v DC fan work with either 12v DV or 24v AC, then I'd be able to keep the fan running. It would be interesting to hear if there's an easy solution to this.

Gyro · « **Reply #36 on:** December 20, 2015, 10:22:01 pm »

I guess either a small 3 terminal 12V regulator or a series resistor and parallel 12V zener diode across the fan. I doubt that small fan pulls much current and the series resistor and zener would dump a bit more useful heat at 24V. Again you could put these in front of the fan to cool them, with no significant dissipation at 12V.

Come to think, if you used a higher wattage zener and lower value series resistor, you could use them as the actual 'heating element' which only dissipates power at 24V but runs the fan summer and winter! Does that count as lateral thinking?

Jay112 · « **Reply #37 on:** December 20, 2015, 10:32:41 pm »

Quote from: Gyro on December 20, 2015, 10:22:01 pm

I guess either a small 3 terminal 12V regulator or a series resistor and parallel 12V zener diode across the fan. I doubt that small fan pulls much current and the series resistor and zener would dump a bit more useful heat at 24V. Again you could put these in front of the fan to cool them, with no significant dissipation at 12V.

Come to think, if you used a higher wattage zener and lower value series resistor, you could use them as the actual 'heating element' which only dissipates power at 24V but runs the fan summer and winter! Does that count as lateral thinking?

That's an awesome idea! I'm glad to have learned how it could be possible.

I don't think I have any zeners on hand, only regular diodes. I wonder though if some of the PCBs I save from broken electronics might have a zener of the correct wattage. I don't think I have any 12v regulators either.

Would a standard 12v DC wall wart contain either of those 2 components? I have a few broken wall warts that I saved in case I can use the parts in the future.

Otherwise I'll probably add some parts like that to my next ebay order, since they'll probably be useful for future projects anyway.

Your username reminds me of Greek food.

Gyro · « **Reply #38 on:** December 20, 2015, 10:53:50 pm »

I was going to say... you'll probably have to buy the bits (zener anyway). No it's unlikely that a wall wart will have one in, sorry.

Zeners commonly come in 400mW, 1.5W and 5W ratings, the 5W would give the largest package, so the greatest surface area. At 100mA it would dissipate 1.2W, 200mA would double that to 2.4W.I would think that the fan pulls less than 50mA so the resistor could be sized somewhere in the region of 56R 3W would give you 200mA plus a bit for the fan. That would give you a maximum heat output (at 24V) of about 5W. Varying between 12 and 24V would let you tune this.

You'd want to put both the Zener and the Resistor directly in the airflow with long leads to maximize heat transfer.

Quote

Your username reminds me of Greek food.

Haha, thanks. I used to have a bit of a passion for gyroscopes.

Chris

Jay112 · « **Reply #39 on:** December 20, 2015, 11:22:17 pm »

Thanks bro! I appreciate your help!

What do you think of these diodes here? Is this a good one for a project like this?
http://www.ebay.com/itm/50pcs-1N5349B-IN5349B-Zener-diode-12V-5W-DO-15-IN5349-/291496699039

And then I was thinking it'd probably be useful for me to have 5v ones on hand for future projects, since I frequently work with 5v. Does it seem logical to stick with 5W ones, even at 5V where I never work with such high wattages?
http://www.ebay.com/itm/20pcs-1N5339B-1N5339-5W-5-6V-DIP-Zener-Diode-/371384223742

And I've never purchased such powerful resistors before. Do these 3W ones look decent?
http://www.ebay.com/itm/250pcs-50-value-1ohm-1M-3W-3-Watt-Metal-Film-Resistor-Assortment-Kit-3699-/301234991533

Gyro · « **Reply #40 on:** December 20, 2015, 11:32:00 pm »

Yes, they look fine. You'd probably get a better deal from a local electronics distributor though. Digikey or Mouser?

Jay112 · « **Reply #41 on:** December 20, 2015, 11:49:55 pm »

Really? Whenever I looked up prices, I always found Digikey and Mouser to be more expensive. I've only purchased once from Digikey, for an Xbee module.

Like for the 12v 1N5349B diodes:
50 pieces from eBay + shipping = 0.156 cents each
From Mouser (http://www.mouser.com/ProductDetail/ON-Semiconductor/1N5349BG/) I would have to purchase 1,000 in order to beat that price (and then the cheapest shipping method is an extra $5 on top of that).

Digikey required a minumum order of 4,000 for most of them, but for the ones that had smaller minimums they were frequently 50 cents a piece (http://www.digikey.com/product-search/en?keywords=1N5349B).

And then for the 5v 1N5339B diodes:
From eBay they were .275 cents each.
On Mouser I would have to purchase 100 in order to beat that price, not including the extra shipping costs.

Am I missing something? I'm very much a beginner with all of this stuff, so it's very possible I'm overlooking something.

Maxlor · « **Reply #42 on:** December 21, 2015, 12:10:14 am »

Quote from: Jay112 on December 20, 2015, 11:49:55 pm

Am I missing something? I'm very much a beginner with all of this stuff, so it's very possible I'm overlooking something.

Reliability. With Digikey, Mouser and the other brand names you can be sure they're not trying to screw you over (except on price, but at least they're open about that...), you get non-counterfeit parts. With ebay, there's the luck of the draw. There are many excellent sellers in that marketplace, but also black sheep that'll sell factory rejects, slightly mislabelled products (B-grade sold as A-grade, or no grade specified at all) or outright fakes.

Marco · « **Reply #43 on:** December 21, 2015, 12:11:26 am »

I estimate this will only raise temperature a couple degrees (5mm of acrylic, 0.02 thermal conductivity, 100 cm2 surface, 4 watt). If you need more you could try putting the resistors directly next to the sensor and gunk it up with hotglue for insulation, you'd want a thermostat though at that point.

Jay112 · « **Reply #44 on:** December 21, 2015, 12:20:40 am »

Quote from: Maxlor on December 21, 2015, 12:10:14 am

Reliability. With Digikey, Mouser and the other brand names you can be sure they're not trying to screw you over (except on price, but at least they're open about that...), you get non-counterfeit parts. With ebay, there's the luck of the draw. There are many excellent sellers in that marketplace, but also black sheep that'll sell factory rejects, slightly mislabelled products (B-grade sold as A-grade, or no grade specified at all) or outright fakes.

That makes a lot of sense! I'll definitely keep that in mind if I ever start working on more serious projects.

I'm at the stage where 90% of my failures/explosions are due to stupid beginner mistakes, so currently I would prefer to save money and blow out the cheap components, instead of having to worry about blowing out more expensive parts.

Jay112 · « **Reply #45 on:** December 21, 2015, 12:23:35 am »

Quote from: Marco on December 21, 2015, 12:11:26 am

I estimate this will only raise temperature a couple degrees (5mm of acrylic, 0.02 thermal conductivity, 100 cm2 surface, 4 watt). If you need more you could try putting the resistors directly next to the sensor and gunk it up with hotglue for insulation, you'd want a thermostat though at that point.

Thanks Marco! I'll definitely keep that in mind if I don't notice much improvement on the cold days.

I've been brainstorming a little with this idea: I could fairly easily bring a cable from another power source into the dome. Then if I get some 3W resistors I could make a more powerful heater. Then I could use a simple thermostat (I already have a spare on hand) that only turns on that 2nd power supply (which is connected to the heater) when the temperature drops below freezing. Then I could use a powerful heater when it's cold out, and I won't have to worry about overheating or wasting energy when the temperature rises.

Jay112 · « **Reply #46 on:** January 01, 2016, 12:53:51 pm »

Last night the temperature was down to 15 degrees, and the camera image was crystal clear the entire time. I've never seen that happen before I installed the new heater. It looks like it's working! Thanks guys!

Gyro · « **Reply #47 on:** January 01, 2016, 06:59:25 pm »

Thanks for reporting back, a nice payback for all that time climbing on the roof. Well done!

At least you have a better handle on the dissipation required - let's see how it does at 14 degrees and below (climate permitting).

Jay112 · « **Reply #48 on:** March 15, 2016, 12:01:56 am »

Hey peeps - I hope everyone is doing well! I just wanted to give a quick update about the heater you guys helped me make, now that the winter is over.

The project was a huge success. Running on 12v mode the camera was able to get down to 0° F without having any problems, but the image would start to stutter when the temperature dropped below zero. That's a big improvement to how it was before, when the image would start stuttering below 20°.

But then on 24VAC mode, the camera was able to function well even below -10°, which basically means it functioned well all winter. Pretty soon I'll unplug the heater and plug back in the cooling fan, and then I'll be set until next winter.

Brumby · « **Reply #49 on:** March 15, 2016, 07:38:53 am »

Good to hear. Thanks for making the effort to give us an update.

Maybe we should put together a label to put on such projects...

Hmmmm..... I have some ideas

Gyro · « **Reply #50 on:** March 15, 2016, 09:28:53 am »

I love it when a plan comes together, congratulations!

Glad you didn't have to spent the whole winter on the roof.

Thanks for reporting back (I wish more did), enjoy the summer.

Brumby · « **Reply #51 on:** March 15, 2016, 12:36:27 pm »

The light bulb is a free vector graphic ...

Gyro · « **Reply #52 on:** March 15, 2016, 07:24:41 pm »

Huh?


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