#261  
Old 02-10-2016, 09:11 PM
perdrix (David)
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For any UK folks following this thread, the G106 case can be found at Rapid Electronics under their own brand.

https://www.rapidonline.com/rapid-g1...st-box-30-1310

Cheers
Dave
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  #262  
Old 02-10-2016, 11:15 PM
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Patrice, did you measure the temperature in between the two Peltiers?
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  #263  
Old 02-10-2016, 11:24 PM
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Brendan, I generated the latest BOM from the schematic and will double-check each part and update my list with the plan to order the missing parts and then ship you spares. I assume we won't be making many more changes to the parts...

Also we could use a boost DC-DC converter instead of a buck converter, i.e to increase the voltage for the Peltier instead of going down. Efficiencies are usually similar but higher voltage means lower current for the pins for the same power. It all depends on the choice of Peltier...

edit:
I keep forgetting to mention this, running cam86 from 7.6V or 8V may not be simple as such power supplies do not exist (unless we build a power supply ourselves). On the other hand 9V power supplies can be bought off the shelf and would make life much simpler.
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  #264  
Old 02-10-2016, 11:52 PM
pat30 (Patrice)
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Quote:
Originally Posted by luka View Post
Patrice, did you measure the temperature in between the two Peltiers?
At the junction of the two, no but the coldest temperature with 2 stage was not super -36 ° C.
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  #265  
Old 03-10-2016, 01:03 AM
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Just a guess but is it possible that your Peltiers are not matched, i.e. that the small Peltier generates more heat that the large Peltier can remove. The junction temperature will be quite high then and both Peltiers would be running very inefficiently.

Also I did a calculation of the sensor heat load a while ago. Let me find it, it may be of use for someone...
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  #266  
Old 03-10-2016, 01:04 AM
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Sorry, just to clarify, -36C was the maximum delta T or the temperature of the cold side?
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  #267  
Old 03-10-2016, 01:33 AM
pat30 (Patrice)
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Quote:
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Sorry, just to clarify, -36C was the maximum delta T or the temperature of the cold side?
Delta, otherwise it would have good
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  #268  
Old 03-10-2016, 02:14 AM
flolic (Filip)
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Damn, it's really hard to follow this on 4 different forums

About peltiers, this is my post from CN, explaining how I assembled my own 2-stage TEC:

"Today I tested my DIY 2-stage peltier module. For the first stage, I cut TES1-12704 30x30mm module into 20mm width. On top of that I glued with thermal conductive epoxy another module, 20x15mm TEC1-2304. Both modules are connected in series. Results (without CCD) are promising, with 8V power supply, module draw 2 amps and can easily reach 60 degrees C temperature difference. 15 watts of generated heat I can easily dissipate with my CNC milled housing.
CCD will be thermally insulated and in a Argon filled chamber. Now I am worried about thermal sinking through the CCD pins...
More tests will follow."


So, with peltiers we must concentrate on efficiency, not on a power. CCD power dissipation is next to nothing, main thermal losses are thermal sinking through pins, and through convection. Convection problem can be solved by thermally insulating whole cold side, including sensor. Heat transfer through pins is much harder to reduce. On my next build my plan is to use FFC (flat flex cable) to connect sensor with PCB. That will completely eliminate thermal sinking.
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  #269  
Old 03-10-2016, 02:22 AM
flolic (Filip)
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Quote:
Originally Posted by pat30 View Post
I put pictures to understand:

The heat sink is insert to the box
Attachment 205124
Patrice, what's your plan for pushing enough air over those heatsink fins?
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  #270  
Old 03-10-2016, 02:23 AM
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I found my notes regarding the sensor heat generation, including the heat transfer through pins:
-----------------
The sensor itself is probably negligible. 7mA@15V = ~0.1W.

I am more worried about the heat leaking from the main PCB via the sensor pins. It is a metal connection via 34 pins. Let's try to get a reasonable estimate:
Q = k * A * dT / d (ignore convection, radiation)
k = specific heat = 66 for beryllium copper
A = area (sensor pin = 0.46mm diameter (assume round), A = Pi * r^2 = 0.17 * 10^-6 m^2)
dT = delta T = 40C
d = thickness - how tall are our pins? Assume 10mm??? Longer pins will help.
We get Q = 0.05W for beryllium copper per pin. Multiply by 34 pins to get Q = 1.5W.

So it looks like our heat load for dT = 40C is about 1.6W. Double that as a safety margin to 3.2W.
(for dT = 60C we have 2.3W, 4.6W with double safety margin)
-------------------------------

and then here are more notes regarding a particular TEC from ebay:

-------------------------------
TEC2-19003, 12V, 3A, Qmax = 35W, Tmax = 80C, dual stage, 30x30x6.5mm

We should expect best case scenario of deltaT = 73C. Sounds really good if you believe the ebay specs.
Note that this deltaT would require the total heat load that our cooler needs to deal with 5.2W + (12V*3A) = 42W(note that 5.2W is the doubled heat load at 73C temperature differential).
That will require a smallish CPU cooler. However, we will likely never run the Peltier at this power.
For comparison QHY8L uses 30W max power.
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  #271  
Old 03-10-2016, 03:02 AM
flolic (Filip)
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A little bit of off topic, I present you few pictures to show how I solved cooling and housing on my KAI4022 camera.

Back side of housing is slim but efficient CPU cooler with copper insert. I also used DIY 2-staged peltier module, sandwiched between cooler and aluminium cold finger. Cold finger is screwed to the cooler with 4 plastic M3 screws. Unfortunately, I somehow lost pictures of that detail...

That camera need approx. 3.2 amps (on 12V supply) for cooling, but can easily reach 48C below ambient temperature So I can image at -20C sensor temperature through all year.
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  #272  
Old 03-10-2016, 03:29 AM
pat30 (Patrice)
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I said exactly the same thing GEHELEM yesterday!

60 ° C difference is huge, very good

the fan will be set just above the PCB hole and a lot of holes on the box, my first tests were good, we'll see if it will be like when it's all fitted together.
I put thermal paste between heatsink and case to help a little.

At worst, if that's not enough I would do a tube with the 3D printer to push air into the PCB hole with 1 fan and I would put a second fan to extract.

what I found odd during my testing, if I put the fan 12V (normal voltage) decreased delta : -27 ° C with fan 12V and -32 ° C with fan 9V , even fan, just different voltage means less air flow.

This afternoon I had a new room CCD bigger, with resistance to heat integrated (1.2W) for glass .

Last edited by pat30; 03-10-2016 at 05:18 AM.
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  #273  
Old 03-10-2016, 10:22 AM
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wasyoungonce (Brendan)
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Brendan, I generated the latest BOM from the schematic and will double-check each part and update my list with the plan to order the missing parts and then ship you spares. I assume we won't be making many more changes to the parts....er.
Thank Luka. Yes a 9V DC supply is much easier than a 8V one,

Like your TEC info...does this include ambient temp changes? Summer time can add 25ēC to the outside HSF.

42W TEC yes we can manage this wit ha reasonable computer HSF!

Patrice and Flip...thanks for your info
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  #274  
Old 05-10-2016, 03:00 AM
pat30 (Patrice)
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Just a message to warn you, I am working the box and wanting to put the connector in box (DC and USB) I realized that the box and too small, so you can leave the cable output or take a larger box to put connector in it, ref Hammond 1550Z111.
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  #275  
Old 05-10-2016, 09:25 AM
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wasyoungonce (Brendan)
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Hi Patrice

yes we have been thru this issue. The G106 case is really a little too small and it's difficult to find connectors IP66/IP67/IP68 rated. We wanted this as our case will be sealed.

I see your case is sealed for the sensor so this is not an issue for you but finding connector that will fit....its a headache. Even our on-board connector (JST-EH) height is barely enough space to fit.

We are fixing these issues before we build but yeas you are correct, the case is too small and probably needs a dedicated case like http://www.cloudynights.com/topic/49...era/?p=7330965. Every time I see this I quiver with envious jealousy!

Brendan
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  #276  
Old 05-10-2016, 11:30 AM
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wasyoungonce (Brendan)
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Here's what $64.55 buys you these days!

Anyone know of a cheaper alternate or supplier!

Oh I also cleaned my antistatic mat
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  #277  
Old 05-10-2016, 08:28 PM
Gary47 (Gary)
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Hi Patrice

yes we have been thru this issue. The G106 case is really a little too small and it's difficult to find connectors IP66/IP67/IP68 rated. We wanted this as our case will be sealed.

I see your case is sealed for the sensor so this is not an issue for you but finding connector that will fit....its a headache. Even our on-board connector (JST-EH) height is barely enough space to fit.

We are fixing these issues before we build but yeas you are correct, the case is too small and probably needs a dedicated case like http://www.cloudynights.com/topic/49...era/?p=7330965. Every time I see this I quiver with envious jealousy!

Brendan
Hi Brendan,
Would it make life easier if I made a sealed break out box to attach to the rear of the camera?
I had considered this as a way of mounting a vac/charging valve but didn't give it much further thought but it could give you more flexibility with size and positioning of connector(s).
Gary
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  #278  
Old 05-10-2016, 11:07 PM
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Brendan, E14 stocks Chip Quik. Not sure about the pricing. Ages ago I used to buy it from SparkFun but they don't stock it any more.

edit:
What is the length that you got for $65?

Last edited by luka; 06-10-2016 at 12:58 AM.
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  #279  
Old 06-10-2016, 03:33 AM
osult (Tom)
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Good morning Tom and Gilles....welcome to downunder. Remember we are upside down here so hang on! Oh did I mention the time zone differences.....yeah this can produce disjointed conversations so please be patient, we are 10hrs faster than UK but 10 years behind!.

I think the ATMEGA328 does the "bit banging" timing in lieu of hardware and ASCOM driven timings in cam84/85m. This takes some communication load off the connection. Also the ATMEGA328 is capable of doing more...like on-board TEC cooling control, etc etc.

I've sent invites to our GD with "read" permissions at the moment. Please by all means use what you want but I need to discuss with the other IIS gents on accessing "write permissions" for you.

I think I've already sent the GD invite...please tell me if it does not show up.

Really good to see new members interested. Kinda.."new blood to spill"!

Brendan
Hi Brendan

I havent seen any communication regarding me gaining access to the files on Google drive
maybe you can submit the request again

BTW - an interesting site on all things peltier www.tecpeltier.com
in particular article "everything you've wanted to know about tecs"
Thank you.
Tom
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  #280  
Old 06-10-2016, 09:34 AM
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Morning gents

Gary reality the case size is the issue me thinks adding a sealed volume to a sealed volume wound make it "Frankenstein"....maybe not we can just make it with the G106 but it really is a square peg into a round hole. Next iteration of camera...a dedicated case?

Luka..Ele14 wanted $95 for the lead free 4.5ft Chip Quik kit. I paid $45 + $16 post (from Oritech) for the lead 4.5ft kit. I hate lead free stuff!

Tom I'll re-send a link to you. I looked at our GD and it has you as a shared person...no idea I'll send another. Thanks for the link I'll have a read.

Brendan
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