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Author Topic: 50$ robot questions  (Read 2902 times)

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Offline gajopTopic starter

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50$ robot questions
« on: October 07, 2008, 11:34:59 AM »
Hello, I'm currently in the process of making the 50$ robot, but since I'm waiting for my programmer to arrive before I can finish, I thought I'd post a few pictures and ask a few questions.

So those pictures below attached are of my augmented microcontroller.

What I'm worried about is, I used too fat wires I think (and solder roll, but that shouldn't be as big of a problem), and on some places I managed to burn the isolation a bit. and on others, wires - even though isolated - touch each other. Should I be worried about any of this when I power it up? I don't have a power supply to test it before hand, so I'm wondering if I should use some insulation tape or something to prevent it from melting.

I did use a multimeter and it shows good readings - things that are connected (besides resistors and LED) have abysmal resistance, those that aren't have above 5k ohms. Can I trust it will remain the same when I power it up?

Another thing I assume I can't measure with my multimeter alone (I assume it uses small current/voltage when it does measurements as to not kill people or damage equipment), so I can't really say if I destroyed my LED or not, as it doesn't show low resistance when I try to measure it - I assume it uses all the juice trying to shoot some photons or whatever.

An alternative I had to use, which I assume isn't a problem, there wasn't a 330 ohm resistor in my local shop, so I just got a 240 and 100, connected them in series, which should be similar. What I'm wondering, if/when I ever get to design my own boards, should I be worried of the maximum allowed power of resistors? I know how to calculate the maximum power that will be made on the resistor itself (at least in a simple theoretical circut), but I'm not sure about the maximum allowed power of the resistor itself. I asked in the shop and I was told it's 1/8 or 1/4 W, but it seemed to me that the salesperson wasn't sure himself. How do you approach that issue when designing boards?

And last but not the least, how do you solder those DIPs or male headers? They proved quite annoying to be made still, I have helping hands, I guess I just don't know how to use them right yet. I have the simplest of solder irons - read: unmodifiable temperature - operating at 30W, it seems to be a bit too hot perhaps, and I think I spent a bit too much time soldering stuff, especially those fckin power buses, so what seems to have happened was that plastic melted a bit as well, causing some of the pins be pushed out a bit - not sure if you can see that from the picture. I assume it's no big deal - they are all still connected, but it's just unprofessional, so I wonder, does that ever happen to you?

Oh and, I'd like to use this opportunity to thank you all, especially Admin for bringing me into this lovely world of solde... robotics.

Offline pomprocker

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Re: 50$ robot questions
« Reply #1 on: October 07, 2008, 11:39:19 AM »
Don't worry...you're on the right track...I've been there done that with this board too.

Part of the fun of making your own board is the mysteriousness about whether it will work or not, and having to resolder things when it suddenly stops working.

If you want to take any of these fun variables out of your robots equation, then buy a pre-made board like the Axon.

Offline Admin

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Re: 50$ robot questions
« Reply #2 on: October 07, 2008, 11:01:32 PM »
It sounds like you'll be fine. Just make sure to check everything as soon as you turn it on. The number one thing to watch for is an overheating voltage regulator - if it overheats, you probably have a short somewhere.

Burned wiring shouldn't be a problem.

As for resistor wattage ratings, I calculate the expected power going through it. For example, if I calculate .65W using ohm's law, I'll just use a 1W resistor. I know the wattage rating because I order everything from online.

As for resistor values, you rarely have to be exact. Ballpark values are perfectly fine.


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