Let's Make Robots!

USB as power source for small robot

I want to use my PC usb port to power a small robot
It contains a buzzer and two solar motors

I have measured that the robobt drain a maximum of 250mA 
Could be there any issue for my motherboard doing this think?

I am very scaryed about to fry the mobo :O

what hapne to usb hub in case of abnormal current drain / short circuit? 

Is there a robust overcurent protection in modern 2.0 usb hub?

Navigate around via IR 2DOF sensor turret; Avoid dangerous slopes via accelerometer
Using a

Geared up Servo

Ok, thanx to Ignoblegnome idea I have done my 360° servo

First i started cutting pieces of PVC, i took a bunch of screw and nuts in order to build the frame for my superservo...

but suddenly Gareth appears in my mind and say: "Use the polymorph Luke..." :O

yeah right, very easy, 10 minutes of work and it's done, very sturdy and precice.


Now i can sweep my sensor in 360° :D

produce chaotic drawings with his pen
Using a
Adding some infos: I use LDR for two purposes: 1) gather random bits in order to affect motor speed (PWM) 2) determine if the robot is stuk. Comparing subsequent … Read more
produce chaotic drawings with his pen
hi all I am mr. Chaos  I can draw chaotic drawings with my ink pen i suck energy from a 1.4 v zinc air cell nice to meet you Read more

NiCd discharge question

i have any questions about the topic


when a nicd cell have to be recharged? i am taking about voltage... 1,15v? 1,10v? 1,05v? 1,00v?  per cell

i have a 3xcell batt pack in a bot , the system self recharge when the voltage reach 3,4v, so 1,13v  per cell

is it an insufficient discharge? which can bring to lazy effect?


assuming that X is the ideal voltage per cell  to decide to recharge..... have i to read X  when the battery is under load or when it isunder no load.

Alternative to L293D for lo voltage apps ?

Is there alternative to L293D ?

what make it unacceptable in many lo-voltage application is its minimum supply voltage + output dropoff voltage!


new project: the critter in the terrarium

 the idea is simple

there is a terrarium (a box)

inside the terrrarium there is a critter which lives forever

the terrarium have a refuel station able to recharge critter batteries

1) when the critter is full of energy it lives:

roam the terrarium and interact with enviroment :respond to sounds, make sounds,  blink lights according ecc

it's able to detect environment light level then respect a day/night behaviour cyle

2) when the critter is low battery it head to refuel station and acquire electrical lock with it

Sound Sensig

I want to find a simple, easy, small, solid circuiti to detect environment sound pressure level

can anyone post a  good schematic?