MacTester57's HemiMac G4

[kiwisincebirth]

As you can see, the CCFL inverter works flawless with a PWM modulated brightness signal (10 kHz) on the green neck wire.

MacTester

very impressive, any reason you went Pwm instead of Digipot control? The major difference being the stability of the output voltage

http://www.picaxeforum.co.uk/showthread.php?14087-Digital-Potentiometers-101

 

[MacTester57]

That dimming touch function is nothing less than brilliant. Excellent!

Thanks. You should implement that too. You will not regret.

very impressive, any reason you went Pwm instead of Digipot control? The major difference being the stability of the output voltage

Thanks. It was the simplest solution and I've seen on the internet that most inverters work with a PWM brightness reference signal too. So I've just tried it and it worked fine.

Here is the wiring diagram:

BTW:
Using the PICAXE touch sensor function, there is no more reason for an expensive Edisen touch sensor, just do it yourself.

MacTester

 

[ersterhernd]

Thx for this info Mactester. A couple of questions...

1. The green inverter wire I have is currently wired for 3.3 Volts. Do the 2 resistors you have shown in the circuit suffice for reducing the 5V from the Picaxe unit down to the 3.7V max? I don't know much about resistance calculation, perhaps you could enlighten me.

2. Does the Picaxe unit need to be programmed to provide the dimming function? Or have you programmed it simply for your sleep LED?


This looks great. I think I'll be doing this. On the interior side of the DVD door, at each end, a small thin sensor could be placed on the backside of the door for the + and - dimming touch function. There'd be no mistaking the touch locations at either end of the door, and the plastic is very thin there, so may work great. Maybe you could test those 2 locations for me to let me know if the touch works or not, before I go ahead with this.


Thanks for your efforts and sharing this valuable solution.

EDIT : Just bought an 08M on eBay for 8 dollars shipped from the UK.


Ersterhernd

 

[MacTester57]

1. The green inverter wire I have is currently wired for 3.3 Volts. Do the 2 resistors you have shown in the circuit suffice for reducing the 5V from the Picaxe unit down to the 3.7V max? I don't know much about resistance calculation, perhaps you could enlighten me.

Yes, the two resistors are here to "divide" the 4.7V (on 100% PWM duty cycle) from the picaxe output to 3.15V maximum voltage for the green neck wire.

2. Does the Picaxe unit need to be programmed to provide the dimming function? Or have you programmed it simply for your sleep LED?

I will have two PICAXE microcontrollers in my iMac Hack. One for the CCFL brightness control and one for the sleep LED.

Here is the small program, that I've written for the PICAXE brightness control. More is not necessary:

Maybe you could test those 2 locations for me to let me know if the touch works or not, before I go ahead with this.

I've not yet tested that. Do some tests on how to mount the sensors will be the next task...

MacTester

 

[MacTester57]

EDIT : Just bought an 08M on eBay for 8 dollars shipped from the UK.

Keep in mind, that you will need the "08M2" type for the PWM functionality! You will also need an "AXE027" USB programming cable (works flawless in OS X after the installation of the required kext). I would recommend to purchase a starter kit.

Happy hacking

MacTester

 

[ersterhernd]

Keep in mind, that you will need the "08M2" type for the PWM functionality! You will also need an "AXE027" USB programming cable (works flawless in OS X after the installation of the required kext). I would recommend to purchase a starter kit.

Happy hacking

MacTester

ooops! guess I wasted 8 dollars on the first one...

I'm not planning LED functionality, just dimming. So I still need the USB cable with that? I'll check out the started kit and wait for your response...

Thx!

 

[MacTester57]

Yes, every PICAXE controller has to be programmed and you need this cable to load the program and for debugging. You should buy this starter kit: PICAXE-08-Starter-Pack

MacTester

 

[ersterhernd]

Thx for your help Mactester, will do. This should be fun.


Cheers!

 

[MacTester57]

Thx for your help Mactester

You're welcome.

Tonight, I've done some tests on how I could make sensor pads that work through thicker material than a plastic bag. The solution were 25mm / 0.5mm thick copper pads (from a G4 Cube PSU shield plate), fixed with 1.5mm doublesided tape to the 1.6mm plexi housing. The program had to be modified too. (The sensor current must be 18yA instead of 0.1yA) The screenshot from yesterday was actualized.

I think, the next step will be to cut holes into the faraday cage (left and right of the Apple logo) to allow the fixation of the pads to the inside of the plastic housing.

MacTester

Edit:
Works too with 20x20x0.4mm plates, glued to 4.7mm plexiglass

 

[ersterhernd]

That's great info, MacTester. I have a piece of the copper shield on hand that I saved, and my picaxe starter kit shipped today. I ordered 4 microcontroller chips altogether. Should be very interesting to see the result. I'm so glad you shared this valuable info, I never even knew such hardware was available.


Cheers!