Let's Make Robots!

Sparkfun FTDI Basic fix

Like another user on the forum, I had problems with my FTDI cable and I couldn't program my Arduino at all. It used to work flawlessly, but suddenly it stopped working all together. It's recognised by the computer and by the Arduino IDE, but whenever I try to upload a sketch it displays the "not in sync" message. However, it works if I plug the FTDI cable into the computer, then click upload, and at the very moment when the IDE displays the sketch's memory info I plug the cable to the Arduino.

Hope this helps 

Any good mechanical engineering books?

I just finished reading this: http://www.allaboutcircuits.com/. It really helped me understand all the electronic background of robotics. Now I feel like reading about mechanical engineering so does anyone have a good book or website to recommend? 

Arduino millis() function doesn't seem to work properly

Yes, this is another of these "Help me with my code" posts. I understand that they are annoying but I have to say I'm seriously stuck on this one. All the code works except for the latest addition which is a timer (sort of). So basically, the robot turns right wile comparing Ir readings. When it detects a decrease in the IR level, it turns left until it achieves relatively the biggest IR readings (meaning that the IR source is right in front as there is more radiation detected when facing it).

Waterproof ultrasonic sensor?

Can I unsolder the transducers from the Parallax PING sensor and replace them by these ones: http://www.parallax.com/Store/Sensors/ObjectDetection/tabid/176/ProductID/755/List/0/Default.aspx?SortField=ProductName,ProductName? They operate at the same frequency. Also, why does the PING sensor have two transducers? I guess one is a transducer and the other is a receiver, but is it the same part?

Differential steering on a 4WD platform

Just a quick question: is differential drive achievable with a 4WD platform? It's an outdoor robot (half a meter in both width and length) and the tires are probably going to be rubber ones. The wheels will be fairly close but I'm still afraid the grip from the tires will be too much. On the other hand I don't want to invest in a complicated drive system.

Turning on a motor using a transistor (question)

I'm building a fire-fighting robot for a science expo and everything is fine so far (at least the electronic part is!) but I`m stuck with the fan motor. I`ve already fried a N3906 (don`t know what I expected).

Comparator circuit question

I have been playing around with BEAM robotics and I have found answers to a lot of my questions but this one still persists. Why does there have to be a pull-up resistor? Can`t I interpret the signal without it? My first guess is that if Vin is smaller than Vref then V+ at the top of the pull-up circuit will be grounded through the op-amp so that Vo is grounded as well. In the other case, electricity flows through Vo and I can use the signal to activate a transistor.

IR LEDs and transistors voltage

Anyone knows the voltage and currents for these devices? There seems to be ABSOLUTELY no information. I bought them from yourduino.com because I told myself I could figure it out but I now highly doubt this. *facepalm*



Can a 3,4V solar panel charge a 3,6V NiMH battery pack?

Can a 3,4V (open circuit voltage) solar panel charge a 3,6V NiMH battery pack?