Let's Make Robots!

Strange battery behaviour

So i just received the battery i was talking about here

it kind of works, but it has a very strange behaviour: basically when i connect it to a load (just a board, nothing intensive), it just doesn't give energy and the board remains off. If then i connect the other connector to the wall plug, the battery "wakes up" and power the board. Then i can disconnect the battery from the wall and it keeps running for hours.

Has anyone tried this batteries ?

Hi, i found this battery online, they came in different shape and characteristics, from different shoppers in hong kong.


As anyone tried them? they look great for the prize.. Also, no weight is specified, anyone knows ?


Android phone as a controller

Hello there :)

I'm on the edge of purchasing an android phone. Looking at specifications around i thought: "Hey but this is the perfect controller for a robot!!" It has an incredible inventory of useful stuff: gps, compass for navigation, wifi, bluetooth and cellular for communication, huge screens for UI, speaker for talking, plenty of cpu, camera, easily programmable, and so on, all packed in a small package, all low power! And all for as less as $200! What do you want more ??

There's only a drawback: there's no simple way to phisically connect a device to peripherals :(

Filtered Linear Power Supply

I was wondering on a site about wireless video transmission, and ended up on this power supply board:


Isn't it very very interesting?? 10 bucks and you have a selectable 3.3, 5, 12 output voltage with input between 4 and 35 volts!

Is there something i'm missing or is it very cool?

Servo mounting for "up-down" movement

hello, i was just wondering: which is the best way to attach a servo to a chassis so that it can move an attached camera up and down (no left-right) ?

Live video streaming for remotely operated robots, solutions?


I recently tried a small videocamera like this one, and i must say that, despite the low quality, they do a decent job, except when heavily shaked.

Now, the main problem is that they have a limited range, and that they have a radio signal on their own, separated from the main robot control. This means that you cannot make a program that behave based on the images, and that the two radio signals can have different ranges.

PPP over XBee, aka xbee wireless

hello, i was thinking about this stuff: if i have two computer with two xbee connected with an usb connection with a FTDI chip, it should be possible to establish a PPP connection over the (simulated) serial port.

Am i wrong?

with 250 kbps (let's say 20 kB/s ?), reduced power consumes and long range, they could make a good solution.

Ladyada XBee adapter, not so good for Pro modules :(

Hi, just a note to warn you, in the case you're interested in LadyAda XBee adapter for an XBee-pro module.

They're advertized as being compatible but that's not really the case. The PRO modules have a longer tail that goes over the capacitor in the bottom, which prevent placing the module at all.

The guide says: "Make sure the capacitor and regulator sit close to the PCB, especially if you're planning to use an XBee Pro module". Unluckly, that's not enought.

8 volt from 12 volt battery

Hello, i have a wireless camera that wants 8 (or 9) volt input. That's a little weird i think.. Anyway, i have a 12 volt battery, is there a way i can get the 8 volt?

I have a spare 3V regulator and a 5V regulator (the classic L7805 something). Is there a way i can use them together to get the 8 volt?

Schematics appreciated :)


Small motor controller/driver with variable speed

Hello, i'd like to have some small driver/controller like the L293D or similar, but that can run motors at variable speed. Does it exists ? A small and cheap board would be ok.

If it doesn't, how could it be built ?


Thanks :P