its from a welder, as you can tell it has two 7 seg displays on it. my mom got it from work so i wanted to use it. i figured i could get it to display temps and maybe put it in my case somewhere. i was wondering how much voltage do you think this would take and where to apply the voltage. i can tell you anything you would like to know, such at the names of the microcontrollers and the colors of the bands on the resistors. http://www.atmel.com/dyn/products/p...=607&family_name=AVR+8-Bit+RISC+&part_id=2004 thats a link for the long microcontroller in the middle, 28 pins in all. the other ones are made from texas instruments, they say "65DVECKe4" on top then below that "SN74LS247n". there are 2 texas chips, each near the 7 seg displays. i can take more pictures if you wuold like, or answer questions you may have. also what would vr1 mean on a pcb? thanks.
vr is a voltage regulator. it is a zener diode and can either be a leaded part, surface mount, or an IC. I would just take a shot in the dark and assume it runs off 5 volts, but that has no reasoning behind it, just a guess. there should be some connector on the board where you would plug in the voltage, i think i see it as the big white/clear thing. It may be labeled as J1 or J followed by a number, as J usually signifies a connector on a PCB.
the white connecter is labeled RC1 to the right of it. i thought it ran off 5 volts or so consdering the main big IC runs with around 4.5 - 5.5 volts. plus i dont think the electronics in a welder would use 12 volts, that would take too much power away from the welding i would think. any idea as to how i could make a connector to plug into that with 5 volts?
look at the power leads on the microcontroller, follow those and see where they go to, if its a filter circuit, then it probably takes 5v in, if its the voltage regulator, then find the datasheet for that, and see what it outputs, and what it can take in.
Can you do a photo of the other side of the board? There's room for a 7805 regulator at the VR1 position but no sign of it. If the 2-pin white connector were power (and it seems a long way from VR1 with no thicker tracks from it) where's the signal inputs?
I don't want to be a party pooper or anything, but I'm wondering a couple of things... 1. This was a freebie from work, does that mean it is even operative? Or was it being tossed because it has issues. 2. The likelihood of you using this board for your purposes without major modification seems slim. Especially anything with microcontrollers. Was the original design for temperature display? If not, it's probably just a good parts board. 3. Given the above, and the type of questions asked, I'd almost suggest it would be less troublesome for the op to purchase either a cheap prebuilt temp board or perhaps a kit rather than try to rework this. Please don't take this negatively, just trying to point out some observations.
Most likely it was display for current and voltage, and depending on the welder it could be a controller board for some high power transistors (like in a miller squarewave unit for example) Next to the 7-segment displays are BCD-7segment decoders, using the part numbers given. If the uC isnt write protected, you could re-program it to do whatever you want, or replace it with one with a similar pinout and make that one do what you want.
That's what you or I would do , but I am thinking if the op is asking about what voltage to use and where to apply it, reprogramming or replacing a ucontroller may be a bit out of reach.
hmmm, so many questions...which ones to answer. i can take a picture of the other side of the board, but there isnt much to the other side. as to what agent 420 said you could be right, evertying cuold be bad and nothing could be functionally working on it. but miller has a ton of money that they can throw away this part. ive thrown parts of sheet metal that prob costed upwards of a hundred dlollars atleast, so im sure they wouldnt care throwing this away. as to why they threw it away they actually didnt, it was in a cardboard box that some other PCB;s were in, i am assuming they were put together wrong or something went bad so they were going to be fixed sometime later. im guessing it displays wire speed and voltage, since thats what you have an almost all welders. my dads used welders before that had digital readoutts so you know the exact voltage and wire speed, plus we all know voltage can have decimals in them, the displays have decimals. so for my best guess it would be to display voltage and wire speed. i could desolder everything on it and reassmble it on another board or use them for parts but there seems to only be 1 thing missing from it, which my mom can find out what part it is, she just hasnt yet since she doesnt have the time to find out. plus i wouldnt want her getting in trouble for trying to find what part and risk getting fired as i would then be out of a job come summer. thanks for all the help and suggestions though. time to follow the power circuit from the ICs.
Sounds like just a parts board then; it'll take quite a bit of work to get that thing to display temperatures, and the circuitry would be different anyway. Kind of like turning a digital alarm clock into a thermometer.
