Could be this, Peter? The graphs look familiar, although the 450D is much more than I remember. So I take back what I said earlier. Still not too onerous. The 1000D curve was of importance to me, as it has been the test bed for my modifications.
I've been chewing over Brent's insistence that the role of the cold-side heat sink is to draw heat energy out of the chamber rather than to push cold air into it. I think that's the essence of his point.
This leads me to wonder, which direction the internal fan should be blowing for optimum effect - towards the peltier's cold side (i.e. pushing the warmer air onto the cold plate) or away from it and towards the camera (i.e. pushing cold air off the back of the peltier towards the camera).
Hi Peter. Optimal would be to blow the warmer air over the plate although both systems would work. Remember, you are recirculating the same air trying to reduce it's temp at each pass, shift the BTU's or calories to the TEC cold side so it gets a bit warmer and moves them across to the hot side to be dissipated by the external radiator.. Energy is energy, it's just a different form, heat > electrical.
Spencers Cameras in the states offers a heat reduction system in their menu of camera mods but their site is very short on specifics. They say it has no additional power requirements so I assume it is a passive device - some kind of internal heat-sink that draws heat away from the sensor Does anyone know anything about these?
Peter
Spencers Cameras in the states offers a heat reduction system in their menu of camera mods but their site is very short on specifics. They say it has no additional power requirements so I assume it is a passive device - some kind of internal heat-sink that draws heat away from the sensor Does anyone know anything about these?
Peter
IIRC Alex Cherney has a Sony NEX5 modded by these folks
IIRC Alex Cherney has a Sony NEX5 modded by these folks
HTH
Cheers
Bill
I've got a 40D en route modded by them for visual plus Ha so it ought to behave like a cross between a 60Da and a Baader modified camera. Here's hoping. I'm building as cooler box for it now.
By the way, I've been looking more closely at that design of Gary Honis - using both the older esky/peltier and the more recent customised box designs. One thing they have in common is that the outside peltier in each case is mounted in air-to-plate fashion - the cold side is mounted to the outside surface of the metal box - with a second smaller heatsink/fan inside. There is no insulation inside either. All the styrene insulation is on the outside.
That means that in both designs, he is using the entire metal housing as the internal heat sink - not just the little sink/fan thingy.
That becomes interesting when you reflect on some recent discussions in this thread about the relative differences in size between inside and outside heat sinks and the implications this may have for efficiency.
The designs I've been working on do not try to cool the entire metal box. They are air-to-air designs - so the cold-side is attached directly to its own heatsink/fan and has no physical connection to the metal box - so the only inside heatsink in the actual box/chamber is the heatsink directly attached to the cold side of the peltier.
And I have insulation both inside and outside the box. So the cooling effect is achieved by what blows straight off the back of the peltier and not radiated from the whole metal box. I don't know how much of a difference this will make. Maybe none. But it just struck me that it is quite different in the cooling mechanism from the Honis model.
As a matter of interest I was able to buy a couple of those old-style polystyrene eskys at Coles yesterday at $7 each. They're a great shape being straight-sided and a good size in all dimensions for slipping in either a Gary-Honis-style custom-made aluminium box or the aluminium basket at the centre of one of those car-fridge devices. I had thought I'd have to cut and shape one but as it is, I can get my metal box inside it with a gap of about 5mm on all sides which I will fill with gap-filling foam when I assemble the finished product.
Peter
Well, cooler box #1 is now plugged in and running. I'm not taking images yet but the camera is in place and all else is ready - as soon as EBay produces my power supply.
The results so far are pretty pleasing. I started at an ambient of 28.6 C and after 65 minutes it is down to 6 C. On the usual basis of halving noise for every 5 degrees, I've already got it down by roughly 90%. The graph is levelling off now. It dropped down in 5 minute increments from ambient to 16, 12 10, 9, and so on down to 6. I expect it won't go much lower than 6. Of course, that's without the camera operating..
The Peltier unit is the one I ordered from the States. Here's a simple graph of that first hour.
The Chinese one arrived yesterday as well and I'm now glueing styrene to the outside of its box. Should be able to give it a run tomorrow I hope. The Chinese unit is not designed as a whole assembly. Rather, it is put together from loose parts and does not have the same degree of thought evident it it. For example, it has taken me a heap of time and messing about to isolate the hot side from the cooler box. But it's done now and I'll get some images up if anyone wants to have a look. I'm attaching a few images of the work-in-progress with the Chinese peltier. This box will take my modified 40D when it gets here.
Brent, I'm sorry if this seems a bit pedantic but with peltiers, the process of cooling (as I understand it) is not to absorb the heat from inside the enclosure and direct it out the back. The idea, as I understand it, is that the bottom side of the peltier device gets cold and the trick is to push that cold into the enclosure via a heat sink/fan on that side. A very different process. And since the peltier produces more heat energy than cold as part of that process (because of the power/enegry used), there is more heat to be blown away by the external fan. So the internal fan, heatsink etc is always smaller in proportion to the out(hot)side one.
So my idea is to generate as much cold air as I can from the peltier and the heat sink in contact with its cold side and push that via the internal heat sink and fan onto the back of the camera.
I hope I don't have this concept wrong.
Peter
Moving heat from the hot side is the key to getting more cooling on the inside, which has worked very well based on his graph. A 20C reduction is quite impressive. I hope that I have not added to the confusion. Is it fair to say that the foil increases the area of cooling medium without adding a lot of mass to the design? Which makes sense.
Peter, where did you measure the temperature inside the box?
Direct cooling avoids the air medium, but has its own issues.
Peter, where did you measure the temperature inside the box?
Nothing too scientific for this first run - I just shoved he sensor into the chamber via the hole I have for cable etc so I don't really know where it came to rest.
If the power supply turns up today I plan to do a more careful test with the sensor taped to the camera's hot-shoe region.
With the question about the use of foil: I speak entirly from instinct and not any scientific knowledge BUT I would have thought the idea of using foil is to create a cold radiator - and if that's the idea, I would have though that mass rather than surface area was the key.
A slight aside, if constructing an aluminium box, should the TEC go on the outside (with cold side attached to the box), or should a hole be made to fit it into? I'm assuming that the TEC shouldn't go inside, as that would leave the hot side contacting the aluminium.
A slight aside, if constructing an aluminium box, should the TEC go on the outside (with cold side attached to the box), or should a hole be made to fit it into? I'm assuming that the TEC shouldn't go inside, as that would leave the hot side contacting the aluminium.
Valid question.
The expensive TEC I bought from the states was well designed for just this purpose. It was possible to screw it into the metal box but have no contact (other than those 2 screws) between the hot side heatsink and the box. Equally, there was no physical connection between the cold side and the box either.
The cheap Chinese unit was less well designed and I had to make a couple of adjustment plates out of plastic material in order to achieve the same level of thermal isolation from the metal box.
My reading of the Gary Honis' description of his metal box and other designs suggested he had the cold side in direct contact with the box because he was using air-to-plate TECs rather than air-to-air. I think that's a flaw in his design.
I'm working on MkII, Rev 1 now. Ordered another TEC because I've reinstated the AS! 120 setup, 20* plus delta under test.
The revision is an internal wrap around aluminium plate for the TEC to connect to. Goes over the top and down under the camera so a lot of area and I've modified the Mk I external foam insulation to fit over the rear of the plastic enclosure. The front is still internally insulated.
I'll post a few pix up when I put it together after the TEC arrives.
Long term I need a power adapter for the 450D so I don't have to open it up to change batteries. It lasts a full night easily but I could insulate if better if I didn't have to make it accessible. Moisture control will be by silica bags inside the enclosure. If I can get a good 10-15* delta I'll be happy.
I'm working on MkII, Rev 1 now. Ordered another TEC because I've reinstated the AS! 120 setup, 20* plus delta under test.
The revision is an internal wrap around aluminium plate for the TEC to connect to. Goes over the top and down under the camera so a lot of area and I've modified the Mk I external foam insulation to fit over the rear of the plastic enclosure. The front is still internally insulated.
I'll post a few pix up when I put it together after the TEC arrives.
Long term I need a power adapter for the 450D so I don't have to open it up to change batteries. It lasts a full night easily but I could insulate if better if I didn't have to make it accessible. Moisture control will be by silica bags inside the enclosure. If I can get a good 10-15* delta I'll be happy.
G'day Brent. I've got a 450D power supply coming but no camera to use it on. Want it?
I've just done a full operation test on the #1 unit. The equipment is a 40D so it's a solid piece of camera, The ambient temp for the test was 27.8 C.
I ran the TEC for 30 minutes before I started imaging. I probably should have run it longer because the temp in the box was still dropping but I was impatient to see how much the sensor added to temperatures. SO the chamber temp at the start was 11.56C. The chamber temperature continued to fall for about 30 minutes and reached down to 10.75C while the sensor temperature started to climb immediately and levelled off at about 21C - roughly 10C above the starting point.
So I guess those who warned me that the sensors ran quite hot were right. The end result of all this seems to be that I am operating at about 15C or a bit more below the temperature that the sensor would otherwise have reached.
It also suggests that the chance of condensation are pretty remote. Even when the ambient temp gets down to say 8C which is a normal winter night here, I will still not have the sensor much below about 3C. Hopefully that works out in the real world.
I've not built my frankenbox yet but aiming for 10-15c cool down around my camera, which should allow me to image pretty much all year. The darks from my 1100D are acceptable (to me!) below 10c ambient.
I've not built my frankenbox yet but aiming for 10-15c cool down around my camera, which should allow me to image pretty much all year. The darks from my 1100D are acceptable (to me!) below 10c ambient.
Not all EOS cameras have a temp sensor. The 350D doesn't and I'm not sure about the 450D but subsequent ones seem to.
You get the data from the EXIF data and I use a tool exiftool to get it although most imaging programs have the ability to tell you the information stored with each file. In Maxim, for example, I can open my RAW files and go to the FITS Header Menu item and it lists the sensor temperature.
The 450D does return temp to BYEos with each image in both C & F to one decimal point.
Power supply, yes please Peter. I'll PM you an address if that's OK, let me know what postage and beer money is and I'll get some $$ across to you.
