SMaR: Problems + Solutions

As the SMaR series comes to an end: here is a second, and final post. I hope you’ve enjoyed it and I look forward to seeing your own robots if you have decided to build one!

The following is a quick guide to problems and their solutions. They are ordered in the following categories:
Planning – Buying – Building – Programming

Planning

I am thinking of buying a robot but I’m unsure if I can afford one.
This is a real thing you need to think about. When I looked at the LMR tutorial and saw they quoted $110 I thought ‘oh well in pounds that’ll be less and I’ll be able to get stuff cheap’.
I was wrong.
In total I spent £115.82 on this robot.
Now I know that is a lot of money, but if you follow my shopping list you’ll be able to save yourself a lot of this.
Included in my costing is £26.48 worth of tools and foam tape. If you can borrow someone’s soldering iron and some solder: do so. I mean on their own they’re not that expensive, but if this is the only project you’re ever going to do with these tools, then try to borrow them.
I made quite a few mistakes. Below is a shopping list that will tell you where I got what and this’ll save you money on shipping costs.
I lost money on buying either wrong parts or one part too many times. Your total cost for parts only should (if you follow my instructions) be £70.96 + £10.27 shipping costs. So for £81.23 you should be able to get all your parts.
So ask yourself if you have this kind of money and if it’s worth it.
I didn’t ask myself these questions and was so focussed on the project I forgot about the costing of it. I mean it was worth it, but it’s a pricey hobby.

I have no experience in building robots or even a vague notion of any of the elements involved.
Neither did I. That’s the point. Read my diary and you’ll see it’s not really needed at all. If you get stuck you can leave a comment on my contact page where I will try to help you. Or alternatively go to the Let’s Make Robots forums to find out if anyone can help you there.
You can do this! Don’t be down on yourself!

I want to start building, but I don’t know where to start.
Read my first diary entry. There I explain what I did. I followed the act page where I will try to help you. Or alternatively go to the Let’s Make Robots tutorial.

Is the robot you’re building remote controlled?
No, the robot I’ve built is independent. It has infra red sensors that measure the distance between it and the objects around it and decides where to go based on this information.

Buying

**Shopping List**
The following is my abbreviated shopping list. You can find comments on each of these components here.

Picaxe
Picaxe-28 Starter Pack Includes project board, Picaxe 28×1 microcontroller, USB programming cable, battery pack (3 batteries) and a software CD (I did not use this).
DIL 330×8 resistor array (yellow chip)
Servo (unbranded S3003 equivalent)

Bitsbox
Male Header Pins
Shorting blocks (scroll down, they’ve called them ‘Jumpers’)
L293D motordriver
Heatshrink tubing

Cool Components
IR Range Sensor – Sharp
IR sensor cable
Female to female jumper wires

Technobots
Inline Geared Motors 200:1 6V
Wheels for Inline Geared Motors (black)

Tools I have bought all my tools in physical shops. I bet you can get them for cheap online or, better yet, you can borrow them off people you know.

I don’t like buying stuff online.
Of course you don’t have to buy all of your components online. The reason I like doing that is that I get to compare prices of a bunch of different places without trekking all over town to find places. Also, you can’t be sure if a shop will have the stuff you’re looking for, so you might have to call in advance to check. All in all I’d say online is easier. But you can go to maplins or your local electronics shop.

Building

I’m having difficulty snapping off those header pins.
Same here buddy. I chipped nails and cut myself several times on this. I ended up biting these off. Don’t do this though, it’s unbecoming.
I suggest using some wire cutters or pliers to try to tear them up. Or ask someone stronger than you.

I don’t know how to solder.
Check out the link Let’s Make Robots provided. It shows you exactly what you’re supposed to be doing.
Things to keep in mind when soldering:
– Heat both parts with the soldering iron first.
– The solder will melt incredibly quickly once heated, make sure you’re quick to withdraw. Also the solder is likely to stick to your soldering iron instead of the thing you’re soldering. Wipe this solder off and try it again!
– When soldering pins to the board make sure you DO NOT have the soldered parts touch each other. For instance when soldering the pins into the A and B ports, make sure each of the pins is soldered separately and don’t just solder the whole bunch in one big blob. This will lead to short circuiting.
– Solder and the soldering iron get HOT. Also, the solder can fall from the soldering iron. Make sure you wear clothes that you don’t mind some burn marks in and that are thick enough to not burn through to your skin instantly. Learn from my mistakes!

All of my chips look similar.
Yeah they do. When you receive your chips, please label them in some way. Also, make sure they are in fact 3 different chips. The one that’s on your board is the 4th, which you won’t need for this robot. Mark them all in some temporary way (I don’t know, put a sticker on them or something) for the assembly and then remove, to reduce any chances of overheating.

The chips won’t come out/go into the board.
Take your chips out using a screw driver or something else flat and long that will go under the chip and lift it out. This will reduce damage to your chips.
When the chips come in the legs are slightly wider than the ports they need to slot into. To amend this just simply bend the legs inwards on a table or something (to ensure they all bend straight).

All of my wires are too short/I’m having issues stripping the wires.
If your wires are too short, lengthen them by stripping the ends off and soldering them together (don’t forget to put heatshrink tube around the cables first!). If you’re having issues stripping the wires (and I don’t blame you those wires are THIN) then get a wire stripper, it’ll make your life easier. I only got mine halfway through the process and I was angry with myself for not getting one sooner.

The body of the robot keeps collapsing.
Yeah, turns out that foam tape I was raving on about isn’t actually that great. My robot collapsed all the time after that first initial adhesive. So just use whatever to stick the whole lot together, but make sure you’re sensible. So:
– No glue, tape, etc. should get into/onto working parts.
– No metal should touch any other metal.
– No parts should interfere with the movement of other parts.
– Ensure you have easy access to your batteries/battery connector and the programming outlet.

Programming

I’ve plugged in the programming cable but my robot remains motionless.
Check the following things:
-Did you install the programming cable driver? If not, it can be downloaded here
-Is the robot ‘on’ so to speak? I.e. did you connect the batteries and did you put batteries in?
-Did you install the correct software?
-Did you hook up all of the correct cables? Make sure the motors are hooked up correctly, i.e. one to the A ports and one to the B ports. Is your servo hooked up with the black cable at the edge of the board? Is your sharp connected the right way round? The Sharp’s cables don’t go into the board in the same order as they go into the Sharp. Make sure you put them in correctly.
-Is your board overheating? If so, unhook it asap! Why are you still reading this! QUICK! Then take the programming cable out and one by one plug things back in, in the order of batteries, motors, servo, sharp. If any of these cause the heating, check that part, check the part it is being plugged into, check if you’ve plugged it in correctly. Check if you’ve done some clean soldering (I sound like my soldering is super neat, but it totally isn’t, check the diary posts for proof).

When I fill in the code on the page, all I get is the Sharp sensor screen and after that nothing.
I had this problem. I’m probably the only one who did, but just in case: The setting of the servo, the debugging of the Sharp and the testing of the motors are all different programs. So run them separately and not as one long sequence. What will happen when you do this is that the servo will do its thing and then the debugging window comes up and after that: nada.

My sharp doesn’t show any readings/isn’t responding in any way.
This is probably because you’ve wired it incorrectly. The way the wires go into the Sharp isn’t the order they go into the project board. Looking at the board from where you plug in the programming cable the wires should go (from left to right) black, white, red. Whereas, looking at the back of the sharp (so the back of the robot’s ‘head’) the cables go in (again left to right) white, black, red. Or any other colour scheme that your cables have come in. Black may be brown, white might be yellow, red might be another colour all together.

Parts of my robot are heating up to uncomfortable levels.
This happened to me. It turned out to be some wrong soldering of the pins onto the board. Make sure you’ve not soldered anything together. Make sure there is no metal-on-metal contact. Also, make sure all of your wires are plugged in correctly. Make sure you only use 3 AA batteries or 4 rechargeable batteries, don’t use 4 standard batteries! Check if all of your project board and parts are clean and no wires are exposed. If all seems in order and you still have this problem: contact someone at Let’s Make Robots.

The wheels of my robot are behaving oddly.
Have you checked you filled in the correct ‘forward’ commands? I.e. are the coding for port 4 5 6 and 7 correct for your robot? If so, is it to do with the motors? Perhaps your motors are too close together and the metal bits are touching? Try repositioning your robots parts a little.

I don’t think this robot is that cool, can I make another?
What’s wrong with you?! This robot is super cool! If you want to build another one; be my guest! You can still learn stuff from this website, but you may want to find other people to talk to to help you with specific things.

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