Well, with inspiration from Paul and Anthony from Southern Celestial Pole and their design lead, I raided the tip for some computer fans and coolers....I have been a busy boy tonight.
I was a bit nervous about pulling the scope to bits to do this, but Paul's astro images speak for themselves.
My scope is well and truly out of warranty now and I am fairly confident I know what I am doing.... :-/
I will be writing a FULL tutorial and have LOTS of photos, so stay tuned folks!
Baz.
Last edited by bloodhound31; 01-07-2008 at 01:42 AM.
Crikey!!! And I was worried about using one of the SCT blowers from OPT (should arrive tommorrow ). Keep us posted on how it works. I would be very interested in your results. Hmmm I wonder what would happen if you added peltier cooling to those heat sinks .
Here are some photos and the power supply I am using. The problem is, I don't know which leads hanging out the back to use. I have a multimeter, but no idea how to use it.... willing to learn....
I am not sure that I would be using that power supply to drive the peltiers. Each of the plugs will have 12V but I dont think they will handle 6amps as most computer hardware have low draw ratings. Have you checked out dick smiths? They have a good range of power supplies which will do the job. I have two, one is a 0 -30V DC 5 amp and the other is a 0 - 30V DC 30amp. Both are adjustable which I am sure you will want to prevent ice forming in the tube and the big one will handle the load easily (I often run 2 telescope mounts, several heaters and a cooled camera with no problems).
Temperature Differential (DT) (Th=27 degrees C) : >=68 degrees C
Optimum Input Voltage (Vmax) (Th=27 degrees C): 15V
Optimum Input Current (Imax) (Th=27 degrees C): 6A
Maximum Cooling Power (Qmax): 51.4W
I also have a wall adaptor (pic below)
I am already running three internal fans off the old computer power supply and three external fans...seems to run them ok.
When I hooked up one peltier to this adaptor on the 12V setting, one side got very hot real quick and the other side got real cold. Can you burn out peltiers?
Temperature Differential (DT) (Th=27 degrees C) : >=68 degrees C
Optimum Input Voltage (Vmax) (Th=27 degrees C): 15V
Optimum Input Current (Imax) (Th=27 degrees C): 6A
Maximum Cooling Power (Qmax): 51.4W
I also have a wall adaptor (pic below)
I am already running three internal fans off the old computer power supply and three external fans...seems to run them ok.
When I hooked up one peltier to this adaptor on the 12V setting, one side got very hot real quick and the other side got real cold. Can you burn out peltiers?
These are the ones I am thinking of (scroll down to Lab Power supplies).
I am a bit worried that with the fans and 3 x 6A peltiers running flat out that you will end up with a smoking mess (your power box has a 20A max rating on it).
Thats what peltiers do. Current flows through the junction of two different metals, one side gets hot the other cold. You can melt anything if you give it enough juice and I suggest that you try to sort out a way to regulate the input power as they will suck as much power as you give them.
Also it was not possible to see behind your backplate from the pic. How much of the heat sink is exposed on the inside??? Are they flat or do they have the small ridge that would have originally just covered the CPU? Judging by the size of your peltiers you will need to remove all protrusions from the heat sink and make sure that the hot side of the peltier is in full contact with the inside of heat sink. Can you get the hot side outside of the tube? It would be self defeating if both were inside as one side would be cooling it down whilst the other side heated it up.
About the info you posted above.
The first one I think relates to the difference in temperature between the hot an cold side.
The second one simply tells you to run 15V for maximum cooling.
The third one states the optimum amperage to achieve maximum cooling.
The forth one is simply a measure of its cooling power.
I have vague memories of Th and Qmax from thermodynamics at uni but they are easily forgotten unless you use them frequently.
Neat design. I couldn't work out if you had cut the heat sinks into the back plate or not. Should work a treat.
I think you may pop a few fuses at the very least if you use that power supply with the peltiers and fans running flat out. It only produces 12V anyway which is less than optimum in any case. Can you rig up a voltage input control? That may restrict the draw if you include some resistors along the line and that will reduce the load on the power supply.
Here are some photos and the power supply I am using. The problem is, I don't know which leads hanging out the back to use. I have a multimeter, but no idea how to use it.... willing to learn....
P.S. Yes, I do have internal fans.....
dont use the wall adaptor! peltiers need lots of amps and they *will* kill a power supply that isnt giving it enough, especially if you put a heat load on the cold side.
the yellow is +12v
the red is +5v
the 12v rail is the one your after, 8a will be really pushing it with what you have there, plug everything in and fire it up but keep your hands on the yellow wires
if they warm up at all turn it off immediately and get a bigger supply.
(not important for the supply you have but just if you buy a more powerful one which i think you will need to)
to get an atx power supply to run without plugging it into a mainboard you will need to bridge the green wire on the biggest (24 pin) connector to any black wire (in the same connector)
Ah at last a tech guru, I was starting to get worried there . Monoxide has given sound advice and I really think you should consider a purpose built power supply. Look on the bright side, if you get a good one (ie lots of grunt) you could virtually power everything (scope, cameras etc) off the same supply which could cut down on power adapters and chords all over the place.
I bought some bits and pieces from dick smiths and made up a box with 4 pairs of outputs which connect using banana plugs. The box connects directly to the power supply and I run my scope, seven oaks dew controller with heaters (usually 2, one for the corrector and a small one on the eyepiece or camera) , peltier cooled camera, jmi smart focus and often my ETX at the same time. I have made short cables that plug into the box via banana plugs and each has the female part of a cigerette lighter type connector on the other end. That way all my bits and pieces retain the male end of the cigerette lighter connection which can be used when mains power is not available.
Its always an adventure when you pull something apart especially when everyone tells you not too . Get a power supply that can supply the greatest amp rating at about 15V as that should suit your purpose perfectly ( I saw some 25 - 30A models in monoxides post and I know dick smiths have a 30 amp version). Keep us updated on you progress as I would really like to know how it all turns out. I have taken the easy road and purchased a cosmic one (Lynmax) blower from OPT which arrived today . I will give it a shot shortly.
It should be noted that I am not the first person to attempt this mod, nor is it my idea.
Full credit for this mod must go to Paul Haese Southern Celestial Pole. I am very grateful to him for the inspiration to attempt this. He and his friend Anthony Welsey pioneered this Mod and allowed folks like me to humbly follow in their lead.
I can only hope to pass the baton to the next bloke as they did for me.
I know Paul has been using the peltier system for 12 months now and has never got ice on the inside of the tube, winter or summer.
He has also been using a computer power supply for the same amount of time and has not melted it down.
In the first instance I think we just took the liberty of setting up a "Dad joke"
In the second instance I am simply concerned for your safety and loss of all the hard work you have put in to the modification. Sorry but I am a science teacher thus naturally always err on the side of caution (e.g. will little Jonny set Marys hair on fire, will Olivia electrocute Shawn to see if he cries etc). Believe me being the only adult in a room full of 32 excited munchikins running around wildly whilst carrying beakers full of 6 molar HCl is a frightning experience that will change you forever. I do not have a lot of confidence in subjecting a power supply to such a load if it is not designed for the task. It could be exciting but I would't recommend trying.
). Keep us posted on how it works. I would be very interested in your results. Hmmm I wonder what would happen if you added peltier cooling to those heat sinks 
. Monoxide has given sound advice and I really think you should consider a purpose built power supply. Look on the bright side, if you get a good one (ie lots of grunt) you could virtually power everything (scope, cameras etc) off the same supply which could cut down on power adapters and chords all over the place. 
