Using a heatbed froma 3D printer to control condensation on my machines

[I.M. OUTAHEREParticipant @i-m-outahere]

Here in Sydney Australia we have just gone through a few weeks of wet cold weather which has caused some condensation issues in my workshop , i have the machines covered with tarps and moisture absorbent devices in under the tarp but still got some condensation – fortunately i coated my machines with lanotech just before the weather change so no damage done .

I was reading through one of my electronics catalogues yesterday and notice a kit for an arduino based condensation control unit for telescopes and this has got me thinking about how i could adapt this unit to keep the moisture at bay in my workshop.

The kit simply measures humidity and temp then switches a small heater ( 5w resistor ) on to keep the telescope lenses warm or above the dew point – it uses pwm to regulate the power to this resistor and has a thermistor attached close to the resistor so the arduino can measure the temp of the resistor as well , i want to expand that capability to switch something a little more powerful on to heat up the air under the tarp on my machines but what to use as a heater ?

Ideally i want something that uses low voltage – less than 32v would be nice and there are a few options like pet heaters , lights and small heater elements , l had a look around on ebay to see what was availlable and how much it would cost then it struck me that i have a couple of heated beds for my 3D printer that mighrt work .

I set them up with a multimeter in circuit to measure current draw then connected a power supply and slowly cranked up the voltage . I settled on 5volts and the current draw settled near enough to 4amps (20W ) with a temperature of 30 – 32 deg celcius ( depending on where i measured it ) . The controller aims for a temp 6 deg celsuis above dew point ( 11deg c ) so looking at around 17deg c.

My questions are,will it work ? Will the heatbed be big enough ( approx 200mm x200mm ) ? Is there a better way or better heater to use that uses minimal power , cheap and safe to use ?

Any thoughts ?

Ian

[I.M. OUTAHEREParticipant @i-m-outahere]

[Michael GilliganParticipant @michaelgilligan61133]

The 3D printer heatbeds are an interesting idea

This also looks promising: **LINK**

http://vi.raptor.ebaydesc.com/ws/eBayISAPI.dll?ViewItemDescV4&item=263094395712

MichaelG.

[BazyleParticipant @bazyle]

A printer heater is specialised and flat which makes it expensive for what it does. A 24v bus or lorry headlight bulb run at low voltage will provide a cheaper low power resistor, also mains bulbs and oven elements all provide a resistor for low voltage use.
Also beware things with soldered tracks which often become the point of a corrosion failure.

[I.M. OUTAHEREParticipant @i-m-outahere]

Interesting idea that Michael , i have also seen IR bulbs for reptile enclosures – i need to go back and re – read the article by SOD in mew about moisture controlas he did a a fairly comprehensive test on the subject – i'm not sure if it is the parent metal or the air you really need to heat up . I did a basic test today by wiring up the heatbed to a PWM controller and set it up so it was drawing 1 amp from a 15volt switchmode supply and this gave a temp setting of around 35 c, i then set it up under the tarp of my mill ( chester lux sort of size ) and added a digital thermometer that can read from a remote sensor and a sensor built into the unit ( basically a fridge / freezer thermometer ) . This gave me a reading for under the tarp and ambient room temp outside the tarp which was 21c approx , i then turned on the heater that was set up on top of the mill vise sitting on a piece of plywood .

It took a little while but after after two hours the temp had risen to 28c which considering all that cold metal acting like a giant heatsink i thought it was pretty good .

Bazyl , thank you for your input and ideas , i will also take a look at a H5 headlight globe ( i have a few spares .) and there is also the halogen globes used in downlights to play with , i was thinking that the heater bed has a bigger surface area, fairly robust , may use less power and being driven with a very low current sowould be long lived and they are fairly cheap .

It looks like i need a data logger to go with this test to give some solid info to work with !

[Ian S CParticipant @iansc]

A few yearsago the old church organ (low tech electronic) suffered from condensation in the winter time, so I fitted a 25W 230V bulb from a sewing machine in side the organ near the circuit boards, worked well until we got rid of it, replacing it with a pipe organ that actually needs from time to time, a bit of moisture.

I have something that might work, it's a little hot plate thing for keeping your coffee warm, I got it to run a LTD hot air motor on, it is 230V,  18W. I'v just switched it on, and discovered why it sometimes doesn't heat, it switches off if you take the weight off the heating area, the coffee cup needs to be fairly solid, and mostly full to switch it on.

Ian S C

Edited By Ian S C on 06/07/2018 13:41:50

[Michael GilliganParticipant @michaelgilligan61133]

Posted by XD 351 on 06/07/2018 09:43:49:

… i'm not sure if it is the parent metal or the air you really need to heat up …

.

My simplistic guiding principle is that if the metal is at a lower temperature than the dew point of the immediately surrounding air … condensation will form on the metal.

Therefore, I favour heating the metal.

MichaelG.

[SillyOldDufferModerator @sillyoldduffer]

Posted by XD 351 on 06/07/2018 09:43:49:

… I need to go back and re – read the article by SOD in mew about moisture controlas he did a a fairly comprehensive test on the subject – i'm not sure if it is the parent metal or the air you really need to heat up . …

Condensation occurs when you have particular combinations of temperature and humidity. To stop condensation, you may need to manage both. I wrote the MEW article partly as an example of Arduino usefulness, and partly to highlight the need to engineer condensation counter-measures rather than blindly repeating what worked for someone else. Their circumstances might be very different to ours.

Firstly, get rid of the water if you can. My gut feel is that removing water is likely to be the best approach in most circumstances, though not all. Depends where it's coming from: burning may be the major source of dampness in some workshops, or the moisture may be natural. Damp proofing and better ventilation is often enough in the UK, but may not make much difference in Sydney. If the air outside is humid, better to minimise ventilation and run a dehumidifier. Putting a cover over the equipment keeps water away from the metal by reducing air-flow. Trouble is you have to remove the cover to start work.

Secondly, control temperature to discourage condensation. Water condenses on metal when the metal surface is cooler than the air. You can much reduce condensation by maintaining the whole workshop at a constant temperature; the downside is the cost. A cheaper but less effective way is to ensure that equipment is always slightly warmer than the air, which can be done by applying a small source of heat to the equipment. Although low wattage lamps are popular for this, proper black heaters are safer in a workshop. Not perfect because unheated tools are unprotected.

Thirdly, most condensation occurs when temperature and humidity change. For example, my UK workshop is unheated leaving air and contents at a fairly constant temperature, much reducing the risk of condensation. However, if in winter I were to switch on an electric heater in a cold workshop, the air would warm more rapidly than the lathe, and condensation would form on the lathe. Instead I wear a coat and suffer. In Sydney, you may have more difficult conditions; high humidity with hot days and cold nights? If that's the case the temperature of your metal equipment may not keep up with rapid natural air temperature changes and get wet every morning when warm air hits cold metal. In the moderate UK insulation often helps stop condensation by reducing temperature swings inside the workshop; I don't know how well it would work in Sydney. If large temperature swings are your problem, using a heater to keep your machines slightly warmer than the air might be a better approach.

When money is no object the best solution is to air-condition the workshop. Send for a professional and do what he says! Air conditioners chill or warm air as necessary to maintain a constant temperature. Chilling the air also removes water.

An Arduino isn't essential to any of this, the advantage of using one is reduced energy costs: with humidity and temperature sensors, it can switch on only as and when needed.

Health and Safety note: ensure unattended electrical equipment, especially a home-made heater, can't start a fire.

Dave

[DMBParticipant @dmb]

Hi all,

I am in Brighton, East Sussex, England. Very hot and sunny here on South coast. Looked for something in workshop yesterday and glanced at very cheap humidity gauge. It read 55%, unusually low due to recent good weather. It is a wooden garden shed mounted on low brick walls with strips of felt as a damp course. Roof and walls encased in felt for rain proofing. Inside walls have 3 ply plywood nailed to inside frame and cavity tightly stuffed with fibreglass attic insulation. Apex roof has thick sheets of polystyrene insulation. Mill and bench drill covered by thick old plastic bags, originally held sand and ballast. Main work bench and MLS 7 covered by thin strips of plastic sheet originally wrappers for rolls of Wickes fibreglass insulation.

Only the mill is heated 24/7/365 by home made device. Can't switch off as I always forget to put it on when needed. Longish rectangular box of 3 ply scraps glued together with holes in bottom to fix 4 off brass bayonet lampholders wired in series. 4 old type, edison bulbs of 40W in series glow and produce quite surprising warmth for low cost. Box on drip tray, open side aimed at knee of mill. Been like this for years, no trace of rusting.

Go in shed, switch on ceiling lamp over main bench and small spot light over lathe. Always minimum 2 lights for safety, if one fails. Whip plastic sheets back along right side to work at lathe or bench and ignore mill and drill on left. If I want to use mill, switch heater off and remove plastic bags then move heater so bulbs don't get broken. It would obstruct z movement of table anyway. I find it no trouble at all to remove/replace a few plastic covers. Most hand tools stored in toolmakers cabs and other boxes in house where central heating looks after rust threat. Just carry a toolbox out to workshop with say, taps and wrenches, dies and stocks, a few other items needed. Boxed sets of drills stay in workshop and are oily so no need for heating.

My biggest problem is me! I don't like extremes of heat or cold. Also try to avoid heavy rain when going out to shed as I would be taking unwanted rainwater into shed.

Jòhn

[DMBParticipant @dmb]

From school days, I think it was I = W ÷ V. R ÷ V ÷ I. Multiple resistances connected in series, add the reciprocal of each resistance to get total, then calculate series Wattage. All I do know is that I get adequate heating of mill for a damn sight less than an individual 40W or 60W bulb and keep the running cost down.

John

[I.M. OUTAHEREParticipant @i-m-outahere]

Once again thanks for the comprehensive and informative replies !

I think i now know what is happening in my workshop , it is a fibro shed that has open eves and runs north -south so the sides are facing east – west . The air temp inside would follow the air temp outside fairly closely as it drops at night but when the sun comes up the side and roof of the shed cops it full blast and this means the shed heats up rapidly and the air temp inside rises rapidly as well but the machines stay cold .

I remember seeing this happen about two years ago i was out in the workshop early in the morning and took the cover off my lathe to use it and almost immediately right before my eyes condensation started forming on the bare metal surfaces ! The plastic tarp may have acted as an insulator so the air outside was able to rise a few degrees without affecting the air temp under the tarp , when i removed it the air temp spiked causing the condensation ! Stupid me didn't think of that ! I actually put a heater on to warm it up – possibllity the worse thing i could have done !

I have some absorbent type moisture control units on all of my machines that i recycle on regular basis but there is only so much that they can do especally in winter time .

One really weird thing is my lathes and mill are covered and suffer condensation issues but my drill press is not covered and i can't remember ever seeing condensation on it – maybe it is because of its lighter construction the metal heats up a bit faster and doesn't lag behind the air temp as much ?

SOD ,

What do you mean by a black heater ? I Googled it but only got a lot of heaters painted black !

I might have to buy my machines a "lekky " blanket – poor things are getting cold 😄

Ian sc,

I could have used one of those cup warmers the other day , i was playing around with a project and kept forgetting my cuppa – went through 3 cups each one went cold ! There is an arduino project in there somewhere !

Ian.

[SillyOldDufferModerator @sillyoldduffer]

Posted by XD 351 on 07/07/2018 00:57:56:

…SOD ,

What do you mean by a black heater ? I Googled it but only got a lot of heaters painted black !

…

Hi Ian,

I am showing my age. What I think of as a Black Heater now looks to be called a 'Tubular Heater', at least in the UK!

Here they are often found in airing-cupboards or used to provide frost protection. They range in heat output from about 20W up to 200W, and can be accessorised with a useful grill guard. Here's what Amazon UK are selling at the moment.

Dave

[I.M. OUTAHEREParticipant @i-m-outahere]

Thanks Dave , i have never seen or heard of one of those !

With a shape like that it would sit down in the lathe bed very well or using the brackets it would sit on the mill table nicely as well .

It would be easy to set up a controller to turn them on at a set temperature as well so they only get used when needed .

I briefly thought about a heating blanket / bed for pets that could be draped across the lathe bed or mill table but i don't like the idea of a heating element encased in a fabric bag !

Does anyone have any thoughts or experience with using Infrared globes like they use in reptile enclosures ? From what i have read they appear to only heat up the surface they are shining on and not the air around it .

Ian.

[The Novice EngineerParticipant @thenoviceengineer]

My solution to sorting out condensation in my unheated workshop was a De-humidifier that had originally been used to dry out a new build extension.

The machine tools were kept nice and rust free.

As a bonus It collected gallons of pure water, ideal for the steam boiler

[Les Jones 1Participant @lesjones1]

Have you considered using heat sink resistors such as these screwed to the metalwork of the machine. I think raising the temperature of the metal above dew point is better than raising the temperature of the air around it above dew point. They are available in various values and power ratings. You can use a series or parallel combination of these to suit the supply voltage you have available and the resistors you can get at a good price. You could also use a frost stat such at this to switch them on.

Les.

[I.M. OUTAHEREParticipant @i-m-outahere]

Hi Les ,

No i hadn't considered them but they do look promising !

Rather than drill and tap holes on the machine maybe drill out the mounting holes on the resistor and epoxy in some small magnets ? That way it could be completely removed in summer and i could stick them directly to the bare metal surfaces which would put the heat right where it is needed .

What do you think of making up a couple of sets of parallel circuits with the following :

2 resistors on the chuck

4 resistors on the slideways of the bed so one resistor on each slideway @ say 1/3 of the bed length in from each end and another two on the carriage so 3 circuits of resistors in total and obviously i would have to adjust the values so the separate sets of resistors in parallel give the same resistance value as each other and run from a suitable switchmode supply and temperature controlled switch .

We are now heading into spring here in OZ so the condensation issue is not a problem but it gives me some time to build all this stuff and experiment with it , i may even factor some power consumption data logging into it to find what works the best at the cheapest price .

Ideally i would like something that works on 36 volts or less and uses the least power possible so others that follow this who may not be converse on mains wiring can build something similar safely and it uses easily available components like those resitors and the controller .

Ebay here i come !

Ian.

[Les Jones 1Participant @lesjones1]

Hi Ian,
I don't have trouble with condensation in my workshop but when the motor failed on my Seig X3 mill Arc Euro suspected it could have been caused by dampness so I clamped two heat sink resistors to the new motor together with a thermostat using jubilee clips. I use a 12 lighting transformer to feed them in the winter. If you can get some old 12 volt lighting transformers you could connect 3 in series to get 36 volts. (NOTE. If connecting them in series they must be real transformers. Not the electronic ones that seem to be sold now. You can use the electronic ones as long as you do not try to connect them in series or parallel.) For the chuck you could bolt one to a suitable lump of metal that could be clamped in the chuck. A piece of thick walled aluminium pipe that extended inside the chuck would probably be the best way.

Les.

[not done it yetParticipant @notdoneityet]

I don’t quite agree with DMB’s suggestions unless your workshop is a poorly insulated and not damp proof – apart from he is correct that W = VI.

Series resistances are summative – parallel ones use the reciprocal form of calculation.

DMB’s four 40W bulbs in series will provide somewhat more than 10W of power (filament resistance will be somewhat lower than at full power). Running all year round, cost would be almost £14 (at a unit cost of15p) if the wattage was 10 (but might be rather more, depending on the operational summative resistance).

Reduced wattage clearly uses less energy, so is cheaper to run, but the correct resistance will provide the required amount of power and use power according to the wattage. Energy from the grid is not free.

The only gain of lower-powered multiple heaters is that they can be sited in different positions. Running in parallel (effectively separate) avoids the situation where a failure in one heater means a certain failure of the whole circuit. If supplied from a single plug, each should be protected by a suitable fuse, with an adequate fuse at the plug, such that a short circuit in one resistance does not affect the whole load. Machines are expensive, so it is well worth looking after them!

More expensive initially, maybe, but I use a desiccant type dehumidifier in winter in the UK. As SOD indicates (I think), removal of water vapour allows lower temperatures to prevail without condensation occurring. Auto humidity or temperature sensors can be utilised to automatically control the energy used (or otherwise wasted by running heaters 24/365). I have simply run my dehumidifier, by timer, for a couple hours per night in winter time. About 7p per day. It has not been required for the last 4 months. My workshop is adequately insulated and air-tight, so there is no exchange of warm dry air (for damp, cold air) when closed up. I heat the workshop, while working there for longer periods, as necessary. The whole workshop is dry and condensation free, so no need to move out tools, or cover machines – just empty the (effectively) distilled water from the dehumidifier every so often (no drain in the workshop).

I intend improving the automation this winter as I’m increasing workshop floor area by about a factor of two. I need to calculate the heat loss through 100mm of polyurethane insulation (plus the sectional garage walls which are also partially insulated) but I do not expect my electricity running costs to rise dramatically as I add further cheap sheet insulation. Insulation costs are about £3/m^2 as I bought over 20m^2 of 100mm polyurethane foam insulation (ex high-rise building?) for a little over £50. I only buy rolls of surplus loft insulation if the price is around £2. It should not be compacted as its insulation property is reduced by so doing.

My dehumidifier cost about £50, including collection – second hand and not working, but easily repaired at no cost! I have a non-running (at the moment) spare which stands me in for £30. It may be quite surprisig what one can achieve on a small budget.

Edited By not done it yet on 24/08/2018 09:05:18

[Mick HenshallParticipant @mickhenshall99321]

I have used tubular heaters in my garage with some sucess put up under the corrugated roof panels, but have had good results by leaving a small desk fan running in garage seems to work and presume the air flow inhibits the condensation,

Mick

[not done it yetParticipant @notdoneityet]

Heat rises, so if the heaters are at roof height, they will need air circulation to heat at floor level! Most tubular heaters are convectors more than radiators.

Likely the air flow keeps the metal items at the same temperature as the air. That will help, as it is often the case that condensation occurs when the metal surfaces are much cooler than the surrounding air, but air flow is not sufficient alone – the water will condense somewhere if the temperature falls below the dew point – hopefully elsewhere than on your machines!

[David Murray 1Participant @davidmurray1]

If you want to put something on the machine have you thought about a mirror demister pad?

[Peter G. ShawParticipant @peterg-shaw75338]

I use some self-regulating heaters from RS Components – Part No. 360-4059

I have 2 on the lathe and 1 on a lump of ali wedged in the bottom of the milling machine. In addition, both machines are covered with a material (don't know what it is) and a sheet of plastic. Neither machine shows any sign of rust whereas previously, the lathe did indeed show rust signs, even though I used to use copious amounts of WD40..

It has to be said that allthough these particular devices (there are other values incidently) are rated at 10W, they actually run at 19W on the lathe: this is completely within specification.

Peter G. Shaw

[Author]

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