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Old 10-01-2019, 08:13 AM
garymck (Gary)
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PC controlled Flat Panel

Hi,

have just built an Arduino / PC controlled flat pane. Used one of these:

https://www.ebay.com.au/itm/A3-LED-L...MJSy:rk:3:pf:0

Thread here:

https://www.cloudynights.com/topic/5...ak-flat-panel/

Arduino sketch here:

https://github.com/jwellman80/ArduinoLightbox

Can be controlled by Sequence Generator Pro (select Alnitak) or Voyager (select Arduino)

Auto flats here I come!

cheers
Gary
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Old 10-01-2019, 11:33 AM
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multiweb (Marc)
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Can you change the brightness of the panel as well?
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Old 10-01-2019, 12:20 PM
garymck (Gary)
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Yes - SGP has a slider that gives 256 levels of brightness. Trying out Voyager tonite to confirm it does as well..
Gary
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Old 10-01-2019, 01:56 PM
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Quote:
Originally Posted by garymck View Post
Yes - SGP has a slider that gives 256 levels of brightness. Trying out Voyager tonite to confirm it does as well..
Gary
That's pretty cool. I have the same panel but have to hold the power button to dim to the required brightness.
PS: ha I just noticed the power plug is a DIN type plug. I have a mini USB port so it probably works differently although the panel looks exactly the same cosmetically.
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Old 10-01-2019, 04:41 PM
garymck (Gary)
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You have to take off the back and alter the wiring. The internal circuitry is rendered obsolete. The arduino uno provides PWM power to control the light level. The uno is in turn controlled by SGP or Voyager such that automated flats can be taken as part of an imaging sequence.

Gary
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Old 10-01-2019, 05:03 PM
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Good stuff.
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Old 11-01-2019, 04:30 AM
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mswhin63 (Malcolm)
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I have concerns regarding PWM controllers in Astro stuff. Capturing lights are taken on high shutter speeds and could image during a off state of the PWM signal. It may or may not be an issue just a thought.
Really the better option would be current set for light level so that the LED are on continuously.
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Old 11-01-2019, 07:10 AM
garymck (Gary)
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Flats are normally at least a couple of seconds long, taken with a very dim panel, so not an issue....

Gary


Quote:
Originally Posted by mswhin63 View Post
I have concerns regarding PWM controllers in Astro stuff. Capturing lights are taken on high shutter speeds and could image during a off state of the PWM signal. It may or may not be an issue just a thought.
Really the better option would be current set for light level so that the LED are on continuously.
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Old 11-01-2019, 06:52 PM
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jwoody (Jeremy)
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Hello Gary
Did you use the TIP 3055 transistor or something else?
Thanks
Jeremy
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Old 11-01-2019, 07:56 PM
garymck (Gary)
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Quote:
Originally Posted by jwoody View Post
Hello Gary
Did you use the TIP 3055 transistor or something else?
Thanks
Jeremy
Used a TIP35C picked up in error from Jaycar :-) wiring was the same....(but 25 amp capacity is a bit of overkill)

Beware the schematic early in the thread on CN - it is wrong and will kill an UNO. Read post number 5 - I wired it up per the written instructions here.

I believe a corrected schematic was posted later in the thread.

Gary

PS It is really cool watching Voyager change the light level until exposures reach the target ADU
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Old 11-01-2019, 10:44 PM
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Cheers, thank you
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Old 12-01-2019, 12:07 PM
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Thanks guys. Looks like there should be no reason this couldn't replace the manual PWM controller I'm using with my 12V more traditional box-shaped LED lightbox.

Its surprising how much time you can spend on a good night, or early in the AM after a long session, trying to get good flats - particularly if have been shooting NB with LRGB (huge differences in light output required). The naughty solution is just not shoot them - which of course reduces quality of the final data.

Currently image through Sequence Generator so its tantalizing how close automated flats could be. Love how arduino etc are making electronic solutions more accessible to amateurs!
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Old 07-10-2019, 09:01 AM
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Just reporting back - managed to successfully build an arduino "alnitak" clone for my LED lightbox, again using the Cloudy Night thread listed above.

Parts purchased included:

- Arduino Uno https://www.ebay.com.au/itm/Arduino-...53.m2749.l2649

- IRF640N mosfet(s) https://www.ebay.com.au/itm/10PCS-Ne...53.m2749.l2649

- 100 ohm resistor(s) https://www.ebay.com.au/itm/CR25-0-2...53.m2749.l2649

- enclosure for Arduino mega (black) https://www.ebay.com.au/itm/ABS-Circ...kfKFMPYJH-1TfA

- Single mountable RCA plug (Jaycar)


I'm using the Arduino project code from late in the CN thread, which uses a different pin on the Uno (pin 11) and slightly modified PWM timer code (faster pulses to avoid artefacts on flats exposures).

The Mega project box nicely holds the Uno (mounting screw positions are seamless as are the USB and 12V power sockets) along with leaving a bit of space and screw mount for the mounting of the mosfet, as per picture below from CN thread.

Works seamlessly in SGP using 12V in on the Arduino and single USB plug. Very happy so far.
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Old 07-10-2019, 11:10 AM
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The_bluester (Paul)
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I have been meaning to look into building one myself. Flats for my ED72 I have been able to do with a graphics tablet I have lying around but it is not big enough for the SCT. I resorted to sky flats but to get the ADC I wanted at the longer exposure times that make an ASI294 behave it was into twilight and the ADU values changed by a lot over the run of flats. Like 30,000 to 15,000. The A2 panels would more than cover my SCT.

Last edited by The_bluester; 07-10-2019 at 11:51 AM.
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Old 07-10-2019, 01:54 PM
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If you read through that full Cloudy Nights thread, it sounds like the trick with flat panels is finding one with a voltage you can supply easily enough, but also able to continue functioning as you pulse or vary input voltage.

I have a friend thinking of doing similar but large enough for RC12.

Would appreciate any comments from those that might have done it already and have a panel to recommend....


No reason can't build a more traditional LED light box for large scope - ends up bit deeper for decent light difusion versus flat panel though of course....
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Old 07-10-2019, 04:21 PM
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The advantage I see to something like the A2 tracing panel is in an obs it would be able to be mounted for use with my SCT, and anything smaller, given I do plan to build an obs of some description soon. The other idea I had tossed about was building one that was on a motorised arm so it could double as an objective cap so shooting flats would become a matter of parking the scope, closing the cap then switching it on and flat framing away.
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Old 07-10-2019, 05:12 PM
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Agree first is what people with bigger scopes tend to do for automation and convenience in observatories.

Have seen the latter as a DIY project at astrofest with the light panel on flip/flop actuated scope cover.
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