Some time ago I got an email. Yes it still happens.
Someone was having a problem with computer / server fans. These things can get insanely loud, think vacuum cleaner on maximum power. Some of the 40x40mm models spin up to 6000 rpm. Absolutely not an issue if servers are rack-mounted in a server-room, but if you like to keep one of those machines in your personal space, that is a big no-no. So said person replaced these fans with slowly-spinning and silent PC-fans (80×80 or bigger, I don’t really know). But, the server’s BIOS / fan-monitoring wasn’t happy. It thought the fans were failing and forcefully shut the server down.
I was asked if I could build a little something that would measure the tacho-signal of the slow-spin-fans and scale that up to values that match the signal from the previous fans, fooling the hardware-monitoring, making it believe everything was ‘as usual’.
Quite often I run into the problem of getting light to where I need it when inspecting SMD solder joints. The ring-light I built some time ago provides a lot of light, but is too large to get close to the objects of desire.
To all the still young whippersnappers, this was before the internet became ‘en vogue’ and easily accessible. Unless you wanted to pay 20$ per hour for a dialup connection using an analog modem with a 9600-link, maybe even 19200.
The lack of an ISP connector on this board has given me a lot of grief. This little adapter board will solve that problem once and for all. It also provides a couple of through-hole pads for potentially adding some more stuff. Clearance distances to the high-voltage parts should still be tolerable.
You can find the gerber files on the projects page.
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.