Let's Make Robots!

Start Here Problems... Mainly the IR Sensor



Ok, I completely made my robot, everything working properly, except for my SHARP IR Sensor which i fried, so i ordered a replacement one, I hooked it up following the instructions,put in the batteries and put in the code, and now its working just like my fried sharp did, its looking both directions, and moving backwards (even though im positive it should be set to go forward i even just enter the forward code and it went forwards) no matter whats in front of it (or not in front of it) it does the same thing, also it felt like it was overheating (by the way when i typed in the ADC code it seemed like it was working) so i checked my connections and i found something was plugged in wrong, i plugged it right, (I accidentally plugged the IR sensor in wrong) and tryed testing it, nothing happened so i checked the batteries and there must have been a spark or something because it shocked me (making me move my robot a little and the batteries fell out) so i unplugged everything and plugged everything in and checked every connection and made sure nothing was overheating and put the batteries back in, this time smoke started pouring out from the batteries (or thats at least where  it looked like it was coming from) So i took the batteries out, unplugged the SHARP, checked connections, etc. nothing was overheating so i put in the batteries and nothing, the servo didn't even turn, so i used some other rechargeable batteries that i knew had full charge and put them in, still nothing, any ideas to what could be wrong (or fried)??? New Problem

When i plug my robot into my computer and do the readadc command on pin 1, 2, or 3 i get the number 255 when i try it on pin 0 i get a combinations of these numbers: 4, 5, 6, 10, 11, 12, 15, 17, 18, 19 and the combinations switches every 5 seconds no matter if the object it was looking at was stationary for those 5 seconds or if it was moving, but i can see a dim red light in the IR Sensor so i know its working... i've plugged the IR Sensor into every combination of  the 3 pins and have done the readadc pin 1, 2, and 3 on every combination of Sharp connections, (the main connection I've been testing on red blue black or V, Vout, gnd) Any ideas as what could be the problem?


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In The Beginning I've overheated Sharp sensors for like hours and thought they were dead. They're actually very durable from the hell I've put them through. Here's what you do. Apply power only to your sensors and look directly into them and you should see a dim red light in one of the lenses. If you do then it's most likey OK. If you don't then it's surely dead and time to toss it. Also, don't know if this helps but I've had some strange experiences with these plastic battery holders which have made me cautious everytime I use them. I would put rechargeables in and they would start overheating and smoking and the battery holder is not even connected to anything. Yes, the batteries were inserted correctly. Then I would try another battery holder and no problems at all. Something with the terminals or wires in these plastic holders go whack sometimes...........That's right I'm blaming the damn battery holder!

I see the red light, but when i enter the Start Here code (customized to my motors) it does the same thing no matter whats in front of it, it looks both ways, moves backwards, then moves a little forwards

This is just something I have screwed up and is easy to do... The data (signal) pin on the ADC inputs on the 28x board are IN THE MIDDLE! It is not to one side as the outputs are configured. It is Gnd,Data,Vcc  NOT Gnd,Vcc,Data

Just a thought.

Judging from the picture you have shorted V1+ and 0V (GND) with a shorting block. I mean those pin headers that are used to select between 1 or 2 power supplies. This means you shorted your batteries and that's why it's smoking. (I'm kinda wondering why did they put that 0V there anyway.) Move the shorting block to its correct place (the other 2 pins). Check 28-pin project board manual (AXE020.pdf) or pictures of Start Here Bot if you are unsure how it should be.

Also, your Sharp is still hooked up the wrong way. Your Sharp's GND is now connected to analogue input 1. It should be connected to 0V (those 2 pins next to analogue inputs and V1+ that are not connected to anything in your picture (see AXE020.pdf)).

edit: Now that I looked at your picture again it looks like you have soldered extra pin for Sharp's GND (like in SHB). So your Sharp should be fine.


I just tried that and my robot works again! except for the IR sensor i just got yesterday... my robot now looks both directions drives backwards stops, and drives forwards no matter whats in front of it...

That's good to hear. Now you should try only the Sharp sensor just like Chris suggested.


Are you sure it shocked you? AA Batteries can produce spaks and make things overheat but they definitely can't shock you. My guess is you fried the servo and the Sharp. If I were you, I'd take the robot apart and pray the Picaxe isn't dead. As for what caused the problem, it could be anything from a big nasty short to a faulty Picaxe.

Well i have an extra Picaxe Microcontroller (which switching them out makes nothing different) and as for the servo, i don't know how to test to see if its working since my computer gives me the "Hardware Error" and when the batteries are plugged in the servo doesn't turn, which actually made me think that the capacitor on the project board might have been the cause of the shock, and if so i'm pretty sure that would make all the connections bad (Im not certain though) and maybe that would be the reason why my batteries are now overheating, or maybe it has something to do with the battery connection?

Hi RoboRyan,

Bad start...

Seems to be a short circuit. Check all your solder joints --- the 4 connections for the motor on the project board, motor connections, solder joints you have made for the IR on the board, battery case etc.

I guess there is a short circuit between the motor connections on the project board on the bottom side. The 4 motor solder points from the L293D are very close to each other.

Well I checked all the connections and nothings touching, the motors are working fine, the IR sensor solder points look fine, as for the battery case, the springs are all bent back (maybe because they were overheated?) so i switched battery cases and tried to see if my computer would read it (it still wont) and now the batteries are overheating, but nothing on the project board even feels the slightest bit hot, could the project boards battery connector have something to do with it?