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I think I have the power supply part more or less ok. I did it with reference to Dave Cook's "Intermediate Robot Building", chapter on power supplies.
I don't know how to draw the connections tying in the ATtiny84, power supply ISP header, etc. I don't have the headers in yet, etc. If someone would loan me a clue I'd really appreciate it.
-- Edit --I added the Eagle .sch file in case that helps
The supply will never work as it stands - Ask yourself "what is the purpose of Q1 and how does it work".
I'll loan you a clue (if you promise to give it back ), but could you specify the exact components that you want to have on the board and how you want it wired?(A link to something you have used or...).
I'll be drawing it in version 4.16 as every version from v5 is very low on contrast, so gives me a headache to use (from eye strain).You can open it in a newer version, but not the other way around.
The only link I have is about the book, but doesn't show that chapter: http://www.robotroom.com/IRB.html. I don't think he has it on the web cause he wants you to buy the book :-)
I thought it was a power MOSFET that I put there for protection against someone (me) plugging the battery in backwards. My understanding is that it will conduct if the gate has a lower voltage than the drain. I intended to connect the gate to ground, and the drain to 6V, so it will conduct. The book says that this being the case, if the battery is plugged in backwards, the gate will have a higher voltage than the drain, so it won't conduct.Am I misunderstanding that, or did I just get it wrong on the schematic?
What I'm hoping to accomplish is to have some pcbs I can use for projects where I'll be using an ATtiny84. I'd like to have a clean power source, be able to program the chip on the board, and have headers I can plug servos or whatever into.
Sure, but what schematic have you used for making them on matrix board?And what are your plans for the prototype area? (overall size/pad types)(Just need to get an idea of how you want it all connected up).
I didn't use a schematic. This is the first one I've tried to do. I just knew what I wanted to wind up with and soldered wires to make that happen. I'll try to come up with some kind of picture tomorrow. I think I can borrow a machine with Visio on it and maybe use that. If not I'll just draw it out and scan it.
OK, I studied your matrix board photo, so I assume you just want each pin brought out to headers and a strip of +5V and ground each side as well?Do you want the female headers nearest the chip as in your photo?
I'll see if I can find where the programming headers go on the '84 (I haven't used Atmel chips for about a decade myself).
No need to draw anything if the above is what you want, but I need to know how large you want the proto area to be and how you want it connected.
Are you planning on single or double sided PCB?
Here are the Circuit from that book, you got it wrong, the MOSFET is at the front not the back of the circuit.
But on the right is the 7805 output, you can't connect the battery to the output of 7805.
I'm looking for a final size of 5 x 3 inches. I assume that the PCB will make the existing stuff more compact, so I was going to use whatever's left for the prototyping area.
Man I'm starting to feel really ignorant :-(
I made it 4x3 (Eagle freeware max size).Take a look at it and tell me what you need changed (like eg. the footprint of certain components or rearranging parts).Instead of the MOSFET, I made a another polarity reversal protection with a fuse (which you should have anyway) and a diode - cheaper and with a still lower voltage drop.Here's the circuit
Here's the circuit
The diode in the schematic is connected from Vcc to GND, but when I plugged in the battery I started smelling burning diode almost immediately. Seems like the diode should go in series, or did I do something wrong setting it up?After a recent experience with a now-useless breadboard I'd like to be sure I know what I'm doing.
Hi,Quote from: joe61 on March 05, 2011, 06:20:40 AMThe diode in the schematic is connected from Vcc to GND, but when I plugged in the battery I started smelling burning diode almost immediately. Seems like the diode should go in series, or did I do something wrong setting it up?After a recent experience with a now-useless breadboard I'd like to be sure I know what I'm doing.As others have already mentioned, either you mounted the diode backwards or you connected the battery backwards.You cannot just leave out some components and expect it to work as designed for, you need the fuse (all circuits do really).
With the diode and the battery connected correctly, the diode will have no influence at all, as the diode is blocking the current.If the battery is connected backwards, the diode will conduct the maximum current the supply can deliver for a very short while (and keeping the reverse voltage to the rest of the circuit down to one diode drop, which could be anything up to a bit over 1V, depending on what that specific diode drops at the current involved). Then the fuse blows. Without the fuse, the diode would melt down very quickly and short circuit your supply (battery).Whether it was the diode or the battery that got in backwards, there's nothing else in the line of fire, so if the rest of the circuit burned, you must have other mounting errors.
Sorry for my last response, guess I got a little defensive because I'm a bit frustrated over my lack of knowledge. I appreciate your help. I'll just work through it again on my own until I know enough to participate reasonably here.