Firefly MV Mono - Is it worth cooling?

[SnakeyJ]

This is quite a fun little camera and serves as quite a good education/intro in to planetary imaging - the sensor is the Micron MT9V022, which is known to be quite noisy which is very evident once you set the gain up over 12dB. The max exposure is quite low @ 512ms, but the tech reference does say there is a bulb exposure control available via the board header.

Has anyone attempted cooling and are the results likely to be worth the effort. I have a good stock of small peltiers and fans, but would certainly need to make a new case/box to give sufficient free space.

Board Picture:

[Cath]

I think all ccd/cmos sensors benefit from cooling, I was going to try it myself on my MV. If you try it let me know how it goes. The sensor gets quite warm I've found.

Currently writing some windows software specifically for the camera, it's coming on well, just learning the API interface as I go.

[StuW]

Would be interested in this myself for maybe modding the ASI cameras in a similar fashion.

Sent from my HTC One X using Tapatalk 2

[SnakeyJ]

Cath - thanks, I know you have a lot of experience in this area (and other more extreme mods ) so very interested in your opinion and advice.

StuW - I've been looking at the possibility of purchasing the ZWO ASI120MM - some fantastic images being produced with this camera and it looks like it offers some bridge between planetary and DSO (at least as an intro to DSO/long exposure) - I think these are pretty much designed to be peltier ready (fan + peltier + controller and go). I haven't looked into the design too much, but assume the cmos has contact with the chassis for heat transfer (cold plate/cold finger). This camera looks stunning value and hopefully I will save up the euros soon enough

I'm not sure I'm brave enough to attempt unsoldering the CCD in the first instance, so was considering using a short insulated can, with a cpu type cooler and peltier mounted externally on the end cooling a 40mm low profile heatsink and fan internally circulating cooled air around the tin. Fan speed control, peltier supply will be run by an external control board, with thermistors on the external heatsink and firefly pcb to give monitor and set point control. Obviously not as good as getting a cold plate/finger under the cmos, but hoping that reducing the ambient temperature within the can will provide sufficient improvement without having to melt the cmos during the attempted removal.

I would need to add some silica gel to prevent internal condensation and allow a small breather hole, but the intention is the can is effectively a sealed unit with the nosepiece protruding from the top and a sealed gland at the rear for usb, fan power and thermistor cables.. I'll also have a think about internal baffling to direct air flow from the internal fan. The front plate will be screwed in for access and silica replacement.

I have a pair of TEC1-12706 peltiers, though no plan to stack! In theory these give a delta T of 30-40C at 12V 3-4.5A, but I hope that 25C below ambient should be sufficient for most most. This mean dissipating some 40-80W of heat, which should be well within the design of the external cpu cooler.

I expect the all up weight of this is going to be around 600gms, which added to the 400gms of my filter wheel will be a fair load and may cause some deflection on my standard SW/Synta focuser. If I can get it up and running it may be possible to save some weight on the output heatsink/fan combo.

The biggest problem will be dissipating the heat from the CMOS chip, which will be thermally insulated by the PCB to the back and lens housing to the front. I can cut away two side of the lens housing to the front, but don't think I can slip any sort of cold finger under the cmos easilly as its not a nice neat two rows of pins.

MT94022 picture:

However I could cut a piece of copper around this and apply thermal compound liberally and perhaps make a replacement lens holder.

Anyway to late for this blind speculation - definitely welcome any good ideas at this point!

[SnakeyJ]

For the external controller - I think I've found a suitable setpoint TEC controller on Ebay @ £ 10 + £ 20 shipping - though this is simply a relay and will require a 12V 4-6A supply!

http://www.ebay.co.uk/itm/DC-12V-Temperature-Controller-of-Thermoelectric-Cooler-Peltier-7016R-/160871223049?pt=LH_DefaultDomain_0&hash=item2574ac0f09#shId

Manual @ http://www.sino-laser.com/picc/WH7016K.doc

Hopefully this will suffice and allow me to do some comparitive testing.

[SnakeyJ]

I've also decided it was time to get a decent regulated power supply to provide power for my mount, fan, heaters and now the peltier ccd cooler. I looked at the famous maplins XM21x 13.8V 7A @ http://www.maplin.co...aplin XM21X PSU although well reviewed/recommended this does not provide sufficient power at 7A and is quite expensive at £ 42.99. So have plumped instead for the Mecury 13.8V 15A unit at TLC - http://www.tlc-direc...s/SK650659.html which came in at £ 34.20 delivered.

Good job I can pinch the peltiers and heatsink/fans from work as this starts to add a fair amount of cost - though to be fair the PSU has been on my to buy list for a while

[SnakeyJ]

I've been considering how to cool the cmos and think the key is the lens mount housing that attaches to the front of the PCB:

This will effectively block any cool air flow around the sensor, leaving it insulated in a warm pocket of air. I think that without focusing attention here the effort of cooling will not achieve a great deal!

Two options to consider:

a. Cut/file the two unused sides that cover the board - this will create a channel for cool air to flow over the cmos. A small baffle plate could be added to divert the flow through this gap.

b. make a replacement lens housing from copper with the base fitted around the shoulders of the cmos chip (with some thermal compound to aide transfer). A few hours work to attempt this and I'll have to borrow a bench drill and taps to get the thread cut internally for the nosepiece.

I can always add a small heatsink on the rear of the board, but sure the PCB will prove quite an effective insulator.

Unless anyone has a better idea, I think I will test with option a to see what can be achieved with minimal input.

I've got all the main components ready, less the peltier control and PSU. I hope to have a go at rough fit assembly tonight to get a better idea of fit and air flow/baffles.

I'll also post some ambient temperature dark frames with the gain/exposure turned up so that there's a baseline to judge any later noise reductions.

[SnakeyJ]

To enable some sort of final comparison, here are a selection of Dark Frames taken with my Firefly MV Mono prior to any modding taken in Firecapture 22 beta 37. I've set the max exposure and gain and then turned on the options for Gain Boost x2, Signal Boost and Gain Boost using Firecap's direct camera register control:

Red=disabled, Green=enabled and I've highlighted the key lines in yellow.

The images displayed are a representative 200x200 crop from the center of a 752x480 capture @ 16 bits for ease of comparison. Ambient temperature was approx. 19C.

Immediate impression quite a few hot pixels throughout these frames and boy does this camera get noisy above 12dB gain!

[Cath]

Looks about the same as mine Jake.

Lets hope the cooling works!

[SnakeyJ]

Now got most of the parts together for the Mk1 Peltier cooler. This will be quite a bulky prototype and looks like I will blow the 600gms weight budget I envisaged, but should do for proof of concept.

Having searched high and low at work, the old dabs themos cup was a bit of a find at home - big and insulated, it allows lots of room to try and baffle/direct air flow. I will probably shorten this and cap with an aluminium plate to provide a bulkhead between the internal (circulation) fan and the external peltier and cpu cooler. I'll also gland cables out through this plate.

Not quite figured out how best to manage the air flow, but some ideas with the plastic pipe sections and perhaps some foam card. The camera nosepiece will fit through the small end, and will probably be sealed with a clear or uv cut filter.

Hopefully the missing bits will turn up tomorrow and I can start assembly in earnest..

[SnakeyJ]

Looks about the same as mine Jake.

Lets hope the cooling works!

Thanks Cath - I was beginning to feel a bit of a lone blogger.

Not sure if there's a better or standard way to do the darks - but at least a reference to look back at. It's certainly pretty noisy, but reassuring to know your results look similar.

Lots of hope it will show some improvement, but the design of the cmos and lens housing does not lend itself to cooling. Achieving 20-30C below ambient within the chamber should be simple, but improving the dissipation of heat away from the cmos is going to be a challenge.

[SnakeyJ]

Re cooling the CMOS - I had a bit of a brainwave early this morning. The internal fan I have brought is a Startech Universal VGA cooler, this comes with a load of extra bits including copper ram heatsinks:

I think with a small bit of copper sheet and a soldering iron I can convert this into a custom heatsink as drawn below:

I really really hate MS Visio, but struggling to get my head around google sketchup

The contact with the cmos will be flush around shoulder though not a massive amount of contact area. This will also raise the lens housing some 3mm.

It does also make me think I am going about this the long way and that I could probably get reasonable direct contact this way, bend out a little bracket with a peltier directly attached. This could save a lot of weight and make the final device much smaller/neater. As I have the bits I'll test both ways to see which offers the best performance.

[long_arms]

What a great thread! I will follow this with interest as I have a few spare cpu coolers around the house.

Dan

[SnakeyJ]

I got my PSU this afternoon, a Mecury 13.8V 15A from TLC ( http://www.tlc-direc...s/SK650659.html ) - nice quick delivery to the Island and perfectly packed with a copy of their latest catalogue which will make a nice door stop. After letting it acclimatise I fired it up and tested with the multimeter to check all was ok - no probs with Volate output unit at TLC - which came in at £ 34.20 delivered. First thoughts are this feels a little light and flimsy, but I'll comment further when I get the chance to use it under load.

Amazon sent me a note to say the internal fan was dispatched yesterday and should be with me before the 19th - obviously travelling via Timbucktu as Donkey post

I've also ordered some 2mm copper sheet to make the heatsinks.

No word yet from China on the Peltier controller - but all things being equal this should arrive some time next week and I can start testing.

The met are promising a brief hole in the cloud tomorrow, but as its Valentines, the wifes birthday and I have a friend over from Greece the chances of getting out look slim - still lets hope the murk clears early next week and I can do some test imaging....

[SnakeyJ]

Memo on LX/Bulb Exposures: Something for later on perhaps - but I did find a good article on the GPIO header and external shutter control @ Pixhawk

[Cath]

I just hope it's worth it after all the stuff you've got for it lol. It's such a noisy little tiny camera

Still, a learning experience, and a good one one at that

[SnakeyJ]

I just hope it's worth it after all the stuff you've got for it lol. It's such a noisy little tiny camera

Still, a learning experience, and a good one one at that

Cath - absolutely! Probably not financially viable for just one firefly, but depends how you caculate the ROI.

If I add up everything so far including the initial purchase of the firefly the total is probably not far short of £ 100 - which is what I spent on a MA Panetary Imager or could spend on a pre modded SPC900. However, much of this investment in kit can/will be re-used on other/future cameras and other astro gear. The investment and return on time is more difficult to calculate. Hopefully I will end up pushing the firefly a little further and get some visible improvement in my images. At the end of the day I'm having fun and should gain a better understanding of the camera, its limits and a broader knowledge of imaging and electronics.

I hope also in posting here that its of general interest, open to community comment/feeback and perhaps this can lead to further refinements and improvements!

[Cath]

Having fun doing it and enjoying the experience and enjoying the learning is what's it all about, it's not about the monetary value/cost

You also learn far more from the experience than you would reading about how to do it from a book. Go for it !

[SnakeyJ]

My peltier cooler arrived from China today and the internal cooling fan from Amazon arrived yesterday - just missing the copper and aluminum sheet which should arrive this week. Looks like a w/end of experimentation ahead

[Cath]

Well, take it slow and be very gentle with the board and sensor Jake, be very careful not to short the metal onto the board.

Might be worth trying to connect the copper you place on/around the sensor to the boards 0V line so as to act as a screen and not introduce noise. If you do do that then DON'T also allow any connection of the heatsink/metal to any other power source.

Have a play anyway .. just be gentle.

[SnakeyJ]

Cath,

Thanks - excellent idea to ground the heatsink for RF shielding (certainly big enough!) and for remark on not shorting the heatsink to the board. I was going to cover the base of the heatsink in insulating tape (apart from the part that sits on the shoulder around the CMOS), but I've picked up lots of thermal pads which are electrically insulated and might help to take a little more heat away from the PCB. Alterntively I can make a polythene mask to fix to the pcb below the heat sink.

There are lots of other components on this board that will probably benefit from cooling and RF shielding - Once up and running on the bench I can test some of this out and see if the reduction in noise is worth all the effort.

Did you get your GPIO plugs/cables and have you had a go at bulb/LX control?

[Cath]

Did you get your GPIO plugs/cables and have you had a go at bulb/LX control?

I did get the plugs yes, got a pack of them off ebay. Although I haven't thought about bulbing the camera, I'll have a look at that! .. The plug is currently used to power a small laser (laser ranging project) and toggle it on/off but I'll have a look at the datasheets and see how to bulb the camera.

btw Jack, dark frames help enormously with this camera (quick test), so long as the darks are saturated, This test was with a little board camera lens (not attached to any good lens or scope) ..

http://stargazerslou...60#entry1830409

[SnakeyJ]

I did get the plugs yes, got a pack of them off ebay. Although I haven't thought about bulbing the camera, I'll have a look at that! .. The plug is currently used to power a small laser (laser ranging project) and toggle it on/off but I'll have a look at the datasheets and see how to bulb the camera.

btw Jack, dark frames help enormously with this camera (quick test), so long as the darks are saturated, This test was with a little board camera lens (not attached to any good lens or scope) ..

http://stargazerslou...60#entry1830409

Thanks Cath - just found the link ebay link for the plugs, so will get some in as my fine soldering skills are poor to say the least

[Cath]

Thanks Cath - just found the link ebay link for the plugs, so will get some in as my fine soldering skills are poor to say the least

Careful, they are just the plug housing (the plastic bit).

You also need the contact connectors to push into the plastic housing (I already had them from another project). You can get the contacts from somewhere like Farnell ..

http://uk.farnell.com/jsp/search/productdetail.jsp?SKU=1679137&MER=baynote-1679137-pr

I couldn't find any on ebay, let me know if you find some!

The other option is to buy the full plug ready wired from the Point Grey UK contact, but they charge about £7 each for them.

[SnakeyJ]

Careful, they are just the plug housing (the plastic bit).

You also need the contact connectors to push into the plastic housing (I already had them from another project). You can get the contacts from somewhere like Farnell ..

http://uk.farnell.co...note-1679137-pr

I couldn't find any on ebay, let me know if you find some!

The other option is to buy the full plug ready wired from the Point Grey UK contact, but they charge about £7 each for them.

Thanks Cath - by the time I faff around its probably easier to source this one off via Clearview Imaging, albeit at a premium. I've read through the tech reference and register guide, but confused as to whether this function is supported on all the models covered by the guide, but its worth a try!

Just had a look on ebay to see if they were still around, but prices are currently £ 65-90 + delivery. Wish I'd brought two of these at the original price