Sunday, April 29, 2007

Microwave Transformers and PICS

Made progress on making the Welder, and making useful things with PIC microprocessors.

Took a old microwave transformer and chiselled out (none to neatly) the secondary windings and put in 3.5 turns of heavy wire, 4 gauge I think (???) that I had lying around.

On 112vac it outputs 3.96vac. Target voltage is 4v so that is good. I might run it on 240v because the omron solid state relay I have is rated for 200-480vac, it does seem to work fine with 112v lighting a lamp. I think that to run it on 112vac will cut it's 30 amp rating in half. I have no idea how much I really need for the spot welder.

Pic Basic Pro seems to work as advertised and now I can actually program (clumsily) a PIC!


Pic Basic Pro

Finally decided that the only way I could reasonably get into using pics was to get Pic Basic Pro. I learning curve is just to steep with the time limitations I have. I need to be using the pics not trying to figure out C or whatever. Basic is easy and I had some experience with Pbasic with the Boe-Bot. There is some stuff to learn with Pic Basic Pro but not unreasonably so.

I have successfully done the blink the led routine. I set up a SOS morse code program and instead of dit dit dit dah dah dah dit dit dit it was doin a dit dit diiiit dah dah daaaah dit dit diiiit. after doing a bunch of things with the program it occured to me that the signal was inverted and it was flashing when it should be dark and vice versa. I swapped the high and low commands to light and extinguish the led and it worked. After thinking a bit I realized that a basic assumption I had was incorrect about the PIC I was using, I thought that if you used a high it would close the switch to +5v, and a low would open the switch to 0v/no connection. That is half right. It appears to put it to +5v on high and 0v/ground on low. What I had done was put the led to the +5v power supply through the resistor to the pin of the PIC. It would flash on the low command because it was going to ground. Amazingly my progam worked correctly when I reversed the led and connected it to ground.

I also got the ICSP to work. Last few dozen tries it just would not work. (ICSP stands for IN-Circuit Serial Programming) I finally decided that it just didn't make sense that it would not work when it should be no different in how it is connected on the programmer. I traced the wired on the programmer and it was identical in hookup as the ICSP would be on the bredboard. That left the differences. I have a 5 leds on the breadboard and so I disconnected all 5 and the ICSP works. It looks like having them hooked up to the +5v strip might have done it, after figuring out I had them hooked up wrong I rehooked up the leds to the ground and the ICSP works. Will see how it works out. So far so good.

Another milestone for me is to be able to do the actually simple task of hooking up a omron solid state relay to the pic output to flash a 40watt lamp. It is quite novel to me to potentially be able to control "real" power switching. The omron is rated to switch at 5-24v dc, to control a load of 30A at 200-480VAC. The lamp I am flashing is on 125 vac which is obviously out of the specification. I assume it is just a matter of not running anything over 15 amps or so (at half the voltage rated)

I origionally got the omron solid state relay to make a spot welder, but now I am thinking something like this might work as a on/off for the sherline cnc motor. I think I will finish the welder first though. One thing at a time.

Sunday, April 15, 2007

Rad Robot Found

Found a RAD robot out on trash day. No remote but otherwise powers up and goes through it's "boot" sequence of moving everything, flashing lights and speaking. Makes funny noises when I tried a 49 mhz toy car transmitter near it in hopes that it might drive. It didn't. Should still be fun to take apart.

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Progress on Video

Made some progress setting up and figuring out how to get the video to work. Breadboarded the transmitter and it worked. Started taking the sacrificial microcam for use with the rc plane and platform.