any circuit builders out there?

[Guest]

i'm stuck. I've got all the components to build my digital fuel gauge, i've got the schematic and... i'm not sure how to go about putting it on the board? anyone with circuitry experence?

[Dogma]

i'm stuck. I've got all the components to build my digital fuel gauge, i've got the schematic and... i'm not sure how to go about putting it on the board? anyone with circuitry experence?

I've assembled a couple boards, including a transmitter for a tiny b/w video camera. I can't do much else with electronics though. If you can solder, then it's not too hard, provided you have good instructions on what goes where. You mention having the schematic. Does it not show where each component goes on the board?

Maybe I should just ask, what is the first roadblock you're up against? Or maybe even, what sort of questions do you have?

[seuadr]

the schematic shows where everything should be hooked up, but my questions involve the best way to do that. it's all going on a fairly small bread board (not that many components) and i'm not sure what i can and can't do as far as putting them on the board. i'll mock it up and take some pictures and then possibly you would see some glaring issues. i don't really have any specific questions, cause i have no idea where to start

[rustybronco]

http://www.4pcb.com/index.php?load=content&page_id=46

or something like it such as a cad program with a layout plugin?

[Dogma]

the schematic shows where everything should be hooked up, but my questions involve the best way to do that. it's all going on a fairly small bread board (not that many components) and i'm not sure what i can and can't do as far as putting them on the board. i'll mock it up and take some pictures and then possibly you would see some glaring issues. i don't really have any specific questions, cause i have no idea where to start

It's going to be built on a breadboard and not a circuit board? Or maybe a perfboard? I'm going to assume you mean a circuit board that you solder the components to.

Are you OK with soldering? You have an iron rated around 20-40 W?
Do you have a reference for reading resistor codes?

Assuming those two, I'd start with taking an inventory of all the component. This will make sure you really have everything, and will give you practice identifying things. You might sort things out at this stage too.

Start assembly with any components that have short leads and sit right on the board. This would be things like chip sockets or power plug jacks. Start with these because you can't push them around to make room for other components. Where they go will be determined by your instructions. I don't know what you have for instructions sometimes there is a diagram with little boxes showing where each component should go. The nice kits have this right on the board. Sometimes there are just labels next to holes. Resistor 1 goes in the holes labeled R1, things like that. Not sure what you have here. Anyhow, just stick these through the board and hold them in place by whatever means necessary. Once the leads are sticking out the back of the board solder them to the board.

Next do components with long wire leads, like resistors and diodes, and transistors. Bend the wires as required to get them through the holes. Bend them too many times, and they break off. Hope your Radio Shack is well stocked. You have to abuse them pretty good for this to happen though. Once you get the component down onto the board, bend the leads so they hold it in place. You might do a few of these at a time once you get the swing of it. Once you have these soldered in place, trim the excess lead off with some side-cutters, or bend them back and forth until they break off. Make sure that the leads on the component side of the board are not touching each other. You may have to bend things around a bit to accomplish this, it the board is crowded.

Some components have polarity you need to be aware of. In particular, diodes, including LEDs. Sometimes, polarity is marked by a line on the package. ("package" in this sense is the little thing the wires come out of, not the thing the diodes were shipped in.) Other times, it's marked by one lead being longer than the other. Hopefully your instructions explain this. If not, do some Googling, because I can't remember which is which.

After you get it assembled, double-check you work before powering up. Some mistakes can fry components, so check very closely for components to be in the right places and not having accidental contact between the leads. Hunt until you find a mistake, because you probably did. Also, if your solder skils aren't great, make sure you don't have any solder bridges between components that shouldn't be connected. Sometimes these can be cut with little diagonal cutters, but usually you need to re-melt the solder and remove the excess.

Get a solder removing tool from Radio Shack. Because the will be mistakes. There just will be. There are three kinds. One is a squeeze bulb, the other is a sort of spring loaded syringe-looking thing, and the third is a wire braid that absorbs molten solder. The squeeze bulb is hard to control. The wire braid takes too long and doesn't pick up as much solder as you might want. I like the syringe thing, but I've seen quality variation in the units from Radio Shack. If I were buying one today, I would check for smooth operation before I got far from the store. You should be able to compress the plunger without feeling resistance from anything besides the spring. When you press the button to release the plunger, it should return quickly with a solid little thunk. When it's working this thing sucks up molten solder very nicely. The solder will quickly solidify inside. Just cycle the plunger a few times to get it out.

Well, I hope that gets you though it. It's pretty gratifying when it works. Really frustrating when it doesn't. Just be thorough.

[seuadr]

ok. it's actually a perf board, then.

um. i don't have any chip sockets.. but i do have chips. i can't solder them straight to the board?

my soldering is -ok- and i haven't gone out and picked up an iron yet, but i plan on getting a nicer one.

you did accidentally answer one question, though. about the perfboard. i was not sure if i should be using wire or what to connect distant components, but now i see the copper will do it for me and i just need to make a path.

:edit: here is the schematic



they keep resizing the second pic down.. if you can't read the numbers try saving it and viewing it in paint to make it larger, or i can email you the origional.

[seuadr]

another question.. upon closer inspection of my board, it only has copper on one side so i'll have to complete the connections myself with solder or wire.. which would work better? i'm thinking small gauge wire would simplify alot of it for me..

[rustybronco]

another question.. upon closer inspection of my board, it only has copper on one side so i'll have to complete the connections myself with solder or wire.. which would work better? i'm thinking small gauge wire would simplify alot of it for me..

Wire from point to point then solder the connection.

[Dogma]

another question.. upon closer inspection of my board, it only has copper on one side so i'll have to complete the connections myself with solder or wire.. which would work better? i'm thinking small gauge wire would simplify alot of it for me..

I didn't realize you need to do your own circuit layout. I think I'd probably attack that with some graph paper before I started bending and soldering. The schematic is pretty well organized into a 12V rail and a ground rail. I'd probably bridge a bunch of pads together to make those two rails (once the components are on). How far apart to make them would have to be worked out on the graph paper if you want to optimize space. But that's just me. It looks like you have plenty of room on that little board, so you can probably do a fairly simple layout at the expense of a few extra jumpers. Keeping it simple will help keep the mistakes out, of course. But I don't think there's a wrong way to organize it.

Yeah, you'll probably need some small gauge wire to make jumpers for the longer runs, especially where paths need to cross. Radio Shack can hook you up there too.

Uh, the chip can go straight on the board, but be certain of your placement. Desoldering a whole chip is a real chore. I had to do a about a 30 pin DIP socket once. Not fun, and pretty much impossible without a good solder sucker and a hot iron. Even then, I just about destroyed the thing.

It looks like a fun little project. There's not a lot you can do wrong, electrically, as long as you have the right connections and good solder joints. Looking at what you've done so far, I do have one comment. In any other application, what you've got so far would be fine, but this thing is going to be subjected to a lot of vibration (maybe even on a smooth bike). Components way up in the air will eventually break off. You might want to rearrange things so the components are as close to the board as possible. This looks like a low-power circuit, so you might even cover the whole thing in a heavy coat of epoxy once it's working. That might be a nice waterproofing too. If you want to use a LOT of epoxy, you could probably keep going with your current layout and cast the thing into a block of epoxy.

Have fun. It looks like you're getting it figured out.

[bakalorz]

ok. it's actually a perf board, then.

um. i don't have any chip sockets.. but i do have chips. i can't solder them straight to the board?

my soldering is -ok- and i haven't gone out and picked up an iron yet, but i plan on getting a nicer one.

you did accidentally answer one question, though. about the perfboard. i was not sure if i should be using wire or what to connect distant components, but now i see the copper will do it for me and i just need to make a path.

:edit: here is the schematic



they keep resizing the second pic down.. if you can't read the numbers try saving it and viewing it in paint to make it larger, or i can email you the origional.

I would recommend moving the 3914 down 2 rows so that you can solder the LEDs in above it.
If the LEDs will be off the board, I would still lower it one row so that the wires from the LEDs can come in through holes from the top, so that the holes are supporting the wire, not just solder.

I personally like to do projects like this on radioshack board 276-170
(you can cut it smaller with a hacksaw)

Instead of the 5 leds shown, you can use 10 for more resolution, (but you may have to add some resistors to them to prevent overheating the 3914)
If you use 10, you can get them as a single chip with the 10 Leds


About a year ago I made a voltmeter out of two 3914s, if you want I'll mail you the info for it, it may help explain some stuff.

[seuadr]

wow good info thanks. i actually do have a 10pin led for that driver chip.. it's actually the one they recommended in the infosheet for the chip. i was intending on having the led seperate, though yes. I actually am strongly considering using a computer hard drive cable to route the LED to the gauge cluster so i can just have the led's "plug in" to the appropriate place on the hard drive cable. also lets me put the circuit somewhere else.. i was thinking of trying to fit it into the headlight.

[seuadr]

I do have one comment. In any other application, what you've got so far would be fine, but this thing is going to be subjected to a lot of vibration (maybe even on a smooth bike). Components way up in the air will eventually break off. You might want to rearrange things so the components are as close to the board as possible. This looks like a low-power circuit, so you might even cover the whole thing in a heavy coat of epoxy once it's working. That might be a nice waterproofing too. If you want to use a LOT of epoxy, you could probably keep going with your current layout and cast the thing into a block of epoxy.

good idea! i may do that. is there any reason why i could not solder those components on the other side of the board, now that i think about it?

[Dogma]

wow good info thanks. i actually do have a 10pin led for that driver chip.. it's actually the one they recommended in the infosheet for the chip. i was intending on having the led seperate, though yes. I actually am strongly considering using a computer hard drive cable to route the LED to the gauge cluster so i can just have the led's "plug in" to the appropriate place on the hard drive cable. also lets me put the circuit somewhere else.. i was thinking of trying to fit it into the headlight.

I like it. Does it have a dimmer for night riding?

[Dogma]

good idea! i may do that. is there any reason why i could not solder those components on the other side of the board, now that i think about it?

I can't think of a reason not to, except for getting in the way of soldering something else, or maybe if you have a box designed for that little board, there may not be room underneath.

[seuadr]

I like it. Does it have a dimmer for night riding?

no, but it's very directional, and red is a good colour for preserving night vision.