#361  
Old 27-11-2016, 01:52 AM
pat30 (Patrice)
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Quote:
Originally Posted by wasyoungonce View Post
Hi Pat.....excellent work...but hey your hair looks....fuzzzy!
Not the hair, I do not have , sewing thread !
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  #362  
Old 27-11-2016, 09:15 AM
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wasyoungonce (Brendan)
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Thanks Rowland that's excellent.

Brendan
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  #363  
Old 01-12-2016, 08:12 PM
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Finally done the TEC tests. Pretty much TES2-19003 run at 12V, ~2.1A get a delta of 50.2C (-20C and lower) regulated. So running it at -15C (within 10 mins time) should be fine.

Tested TEC with IRF7832...no problems as a switch device. Had to add resistors to gate to lower capacitance but this was not an issue running TEC Vgs @3.0V Pd across TEC was .273V, well within the devices limits.

I did hear a "crack" when re-mounting the TEC...although inspection showed no cracks but I did notice it was a little slower in cooling than my original runs...by ~2C. Ordered another TEC....

Funny thing increasing Vgs did not improve conduction or cooling! Rds on is good for low Vgs on this device.

So final hurdle, need to add FET gate resistors to schematic and its ready to roll!....finally

Yeah baby!
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  #364  
Old 04-12-2016, 11:06 AM
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wasyoungonce (Brendan)
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PCBs done...just not need to double check design rules for fab house and gerbers.

Finally!
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  #365  
Old 06-12-2016, 10:49 AM
flolic (Filip)
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Brendan, can you share your latest PCB design? I've done some work on my own, modifying design that you sent me few months ago...

I have ordered PCBs from seeedstudio a month ago (but they scre*ed something with shipping), so I reordered boards this time from OSH Park and they are in production right now. I expect them to arrive before Christmas.
I gathered all other parts, only boards are missing.

PCB preview from OSH Park:

https://dl.dropboxusercontent.com/u/.../cam86_top.png

https://dl.dropboxusercontent.com/u/...m86_bottom.png
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  #366  
Old 06-12-2016, 12:30 PM
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wasyoungonce (Brendan)
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Hi Flip...no problems..I'll send a link to our Google Drive.

Basically we changed the VT1 to a IRF7832 and tested this using TECs. The reason was the original VT1 as not good enough Rds on (too high) with low gate Vgs from the ATMEGA328 (~3.0~3.3V).

You look like you have already done something like this with Q2? Oh we added 2 extra 100uf ceramic capacitors on DD11 output as per Ukrainian forum.

Anyway you boards look damn fine. Both our layouts are very similar. We are just about to order, probably from PCBWay. Luka is doing this as he's dealt with them before. I've only used OSHpark and futurlec (pls don't use futurlec anyone they have gone off!)

Brendan

edit:
Forgot to ask...have you made any other changes ...kinda something we might have missed?
Brendan


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Last edited by wasyoungonce; 06-12-2016 at 04:31 PM.
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  #367  
Old 07-12-2016, 08:30 AM
flolic (Filip)
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Brendan, thanks for the GD link
In short, layout of my board is just modified version of one of your earlier designs (which is based on original Ukrainian PCB). So yes, all of our boards are very similar.
As you noticed, I replaced VT1 with some of more robust mosfets in SO8 package. I have bunch of IRL6342 transistors, that one should be ok.
I also increased cutout area under the sensor, there is no reason to limit yourself without any valid reason.

I had excellent experience with seeedstudio in the past, but now they screwed something and not responding to my emails..
So I tried OSHPark for the first time, they are more expensive but I will get ENIG finish. They charged me 35USD for three boards.
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  #368  
Old 07-12-2016, 09:06 AM
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Hi Filip.
I uploaded my design to OSHPark just to see if it was ok even though my gerbers look ok in Gerbv. I note they are quite a bit more expensive but they do nice make boards.

The IRL6342 looks to be a good choice for TEC switch. Though I cannot see any gate resistor or gate bleed resistor to gnd? Look it shouldn't matter as it's driven from the ATMEGA328 out but its just good practice to include such resistors to lower stray capacitance, improve switching time and help dampen any oscillations.

But in reality if the PWM is 1Hz....I don't think its going to be an issue.

I actually tried permutations of switching our FET without gate resistors...there was no change to conductance nor package Pd. So take the above 2cents advice with the worth of a grain of salt!

Keep us up to date. Good to see others and their ideas coming together.
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  #369  
Old 07-12-2016, 02:32 PM
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wasyoungonce (Brendan)
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Filip gave me some layout suggestions and shared his layout. His layout is very close to ours and I agree I probably needed to spend a little more time with mixed signal gnds and routing paths for bypass caps...as well as placing fiducials closer to the GND and these caps.

This allows low impedance between the layers and reduces noise loops. I kinda placed gnd fiducials in geometric patterns but I did place more near low sensitive signal areas.

Also my GND planes could have been a little more defined in encompassing the cold finger cutout.

So...we are going with what we have and maybe next iteration I'll get better.

Ok Filip...Luka said he can throw your PCB design onto our batch if you want. It'll be cheaper! Just a thought and the Christmas goodwill is flowing like a beer in a duststorm!

Just PM me or Luka if you want.

Brendan
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  #370  
Old 07-12-2016, 07:20 PM
flolic (Filip)
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Hi Brendan,
Thanks for your offer, but I already have open (and paid) orders on a two different PCB houses
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  #371  
Old 10-12-2016, 02:14 PM
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wasyoungonce (Brendan)
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For the record...PCB orders placed by Luka. Gary is hunting optical glass windows.

We are starting the ball rolling now!

Its taken ;longer than expected but we have done our own PCBs and made improvements suggested along the way.

Finally, like Christmas...its happening! Jeez I hope my soldering is up to scratch!

Brendan
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  #372  
Old 10-12-2016, 02:28 PM
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Also looks to be some new iterations of cam86 already being made by Faddy. A round stackable PCB. Makes it easier to seal the sensor area. Looks very nice but needs a few machined parts.

Cam86 firmware and drivers now appear quite mature and even usable in indi as well as ASCOM.

Also a Cam90 in progress using ICX493A (10M) and ICX613 (14M) sensors.

Damn this really have taken on a life of it's own! Well done to Ukrainians. Now to build it...
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  #373  
Old 10-12-2016, 07:07 PM
pat30 (Patrice)
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My friends, I am happy to present my first picture with Cam86, there is still a little work to do but it is a first.

A very good thing to have increased the capacitors of DD11.


http://www.webastro.net/upload/image...1481443054.jpg

Last edited by pat30; 12-12-2016 at 05:43 AM.
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  #374  
Old 10-12-2016, 08:04 PM
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wasyoungonce (Brendan)
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Hi Pat...looking good.

We added qty 3 places for DD11 ceramic caps on advice and changed VT1 to IRF7832.

We are all looking at getting this working and you are providing inspiration. Our PCBs shouldn't be too long now. Many thanks

Brendan
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  #375  
Old 11-12-2016, 05:13 PM
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Just a quick update, the boards are finished and are waiting to be collected by DHL.
Brendan, I scored us some freebies as well
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  #376  
Old 11-12-2016, 08:46 PM
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Excellent...Santa is early this year?

Brendan
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  #377  
Old 15-12-2016, 01:53 PM
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Exciting..! This is a good little mosfet for cooling. I'm using the DPAK2-7 smd version. Very low Rds(on). Runs barely warm to the touch.

Last edited by rcheshire; 19-12-2016 at 11:04 PM.
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  #378  
Old 15-12-2016, 02:28 PM
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wasyoungonce (Brendan)
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Rowland I think your link is broken.

Luka has received our PCBs.....but...I stuffed up the top and bottom silkscreen layers. I have these files included and they had bytes of data...but no layers were drawn.

Looking at all my other Gerbers..even others I generated that day....they are ok...no idea how this happened...operator error I suspect!
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  #379  
Old 16-12-2016, 02:30 AM
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The boards are here and I spent most of the day soldering.

Step 1: solder the FTDI chip and the 3.3V power
The chip was detected on PC, everything worked fine. The 3.3V regulator is getting quite hot as the voltage is getting dropped from 12V to 3.3V. Bad design but there are several workarounds.

Step 2: solder the rest of the voltage converters
All voltages tested OK.

Step 3: solder AtMega328P, ADCs etc.
I soldered most of the other components but did not finish everything. Also I noticed that I had incorrect DD6 and VT1 so I ordered new ones. Probably won't have them before Monday.
VT1 is used to run the TEC so it is not critical. But DD6 is a show stopper. I suppose I can still flash the AtMega firmware without it and test that.

Also my DMSO finally arrived and one sensor is having a bath. The bottle leaked during the transport and I got the stuff all over my hands while unpacking. I suppose I am going for the "garlic taste ride" .

Brendan, what did you use to clean the sensor after the DMSO application?
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  #380  
Old 16-12-2016, 02:35 AM
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Also Rowland's link did not work for me when I clicked on it but when I copied/pasted it, it worked fine

It is for IRFP7430PbF rectifier.
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