Possibly (and hopefully) the last post in this little hot-air station series. I’ve opened and closed that device far too often – and popped out the chip multiple times in each instance. You see the designer failed to add a programming header!
TO THE PILLORY WITH HIM (or her)!
So I finally decided to add my own programming header – lots of cables involved. Enjoy the images. I also took the opportunity to fix some other issues.
After tweaking some control loop parameters and adding a hard-limit for the temperature (heater cut-off + resetting the error term, effectively restarting the loop), the massive temperature overshoots are a thing of the past.
I declare this a success.
“Some changes (video will come later):”
Improved button response
Display meaningful error message if the wand is not connected (FAN)
Added persistent temperature set-point storage
Tweaked the control loop some more :-)
Display set-point once temperature is within +- 4°C (removes annoying noise on display)
I also had to fix one of the safety-earth wires. To be fair, it probably fatigued due to me dismantling the device many many times.
In part one I dealt with the very basics: fan control, buttons and the display.
Now it is time to attack the business end of this device!
Safety warning / disclaimer:
Please understand that operating a device powered by line-voltage, especially if it is open and you may stick your fingers inside (which you really really shouldn’t), is a potent source of all sorts of bad things of a final nature.
You may severely burn your flesh (not just medium, but well done)
You can start a fire and burn down your house
You can electrocute yourself, then start a fire and burn down your house
I think you get my point.
If you still insist in opening up such devices, there is one rule to rule them all:
Always make sure the power cord is unplugged, before you stick your fingers inside the device. Check for that fact repeatedly. Don’t allow your brain to trick you into thinking that you’ve unplugged the cable some time ago, always check, double check, triple check. If you leave your workplace and come back or you got distracted by something, check the power cable for unplugged-ness again. If you know you cannot trust yourself, cover the power-socket of the device with tape. Then check that the tape is still in place…
BE PARANOID! BE A SAFETY NAZI!
You’ve only got one life – and there is no backup to restore.
No more software PWM, no more LED driver chips, just intelligent LED pixels. These things come with integrated controllers/drivers and support 24bit colors (8bit per R,G,B). This makes projects smaller and is much easier on the microcontroller, no more need for interrupt-driven PWM generation and refreshing etc.
As of late I’ve been making smaller and smaller circuit boards, fighting for every mm² of space. The typical 6pin ISP connector used for programming a lot of the AVR micro-controllers has been getting in the way more and more.
Now that the ‘customs-guys’ have finally released the LED-driver ICs, I can finish this project. 4 Weeks is a looooong time for ‘air-mail’.
If you’re thinking about 100% hand-assembly, start with the LEDs first! Then add all the other small parts, then the potentiometer and as the very last part the IC. Use plenty of flux (paste preferred), clean your tip often and go easy on the LEDs. They burn easily. You’ll probably want a magnifier and lots of light as well.
I charged both the ‘useless’ starter-box and the battery over night and I was lucky ;-)
‘The car’ started instantly.
Went to my local VW dealer / garage and inquired how much a new vacuum pump for the door locks would cost me (without labour), and was rewarded with an estimate of above 200 bucks. Not good. It’s a friggin’ electrical motor with a bit of mechanics and electronics. I can get a laptop for 200 bucks, which is obviously much more complex.
The 2nd-hand market offers these parts for about 40-70 bucks. I’ll think about that. I certainly won’t buy a new non-safety-relevant pump for a 20 year old car.
The more I use this thing, the less I like it. I only get about a minute worth of cranking out of it. The battery claims 17Ah, but given that the charging circuit doesn’t really permit more than say 400mA of current… I can’t really be sure this thing was really full. Maybe the battery is a piece of crap as well.