Let's Make Robots!


Does your bedside table give light when you open it? In a discussion with a carpenter about his furnitures I asked about the usage of electronics in his creations. … Read more

Joule Thief

There is not much to document in this project. I built a Joule Thief....who didn't ;-)

Mine is powered by a LR44 button cell (1.5V) and it light up a white LED which usually needs a minimum of 3.3 voltes to light up.

I just built it to test how long the LED can light with this one battery (it might be interesting for throwies). 

Will update the blog when the battery is completely depleted.

Power on time: January 14, 2012, 3:30PM

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).

Analog Robot Controller
Hello! I made a pcb for Aivot - analog robot controller Parts: 2x 2N3904 1x ferric chloride mix 1x printed circuit Lots of pictures: Printed circuit and piece of … Read more

Transistor terminal naming conventions.

I am trying to figure out how transistors work and have seen the three terminals on a bipolar transistor labelled base, collector, and emitter.

I am having a hard time understanding the purpose of the three, and would like it if someone could explain why they are named this way. I.e. what is basey about the base and what is the collector collecting?

At the moment they just look like three randomly chosen words.


Free Motor Controllers!

I am currently designing some very budget friendly Motor drivers, and to test the design out, I am giving away 10 free drivers! Each driver is a single or possibly dual (5 single and 5 dual) transistor based design, and cost per board is very, very low. If you would like one of these free driver boards, please post in the forum below. No restrictions! Each board ships with a application note so you know how to use it.

A few specs:

Max Voltage: 30V

Max Amperage: 0.6A

do you think this would work if i wired it up to a picaxe 14M

ok this is a circuit i have come up with to try and not use a motor driver for my picaxe,

i will have the base transistors connected to pins of a picaxe 

i will appreciate your input 

Our first 'robot' circuit: What is this Component?

We've been working on a lot of basic circuits, just trying to understand basic electronics.  Almost all of our components are salvaged from old electronics, so it has been slow going, but we are learning a lot!

OPB704 Line Sensor


I have received questions regarding the line sensor that I'm using on my mini sumo bot. Here I will post the schematic and pictures of the board. 

The OPB704:

So after lots of hard-work, frustation, time, spending money on wrong parts; I built a robot. Its a Photovore based on NPN transistors. when its LDRs are pointed … Read more
Detects paranormal energy levels, spirits etc
Update: I got myself a new camera that can take exposures in up to 30 seconds at a time. So I took some new pictures this late night. I found lots of energy … Read more

upgrading from small motor

Let's say I have a motor control circuit that's too small. It could be the motor output of a Picaxe, the adafruit motorshield for arduino or a the innards of an old RC toy. The main thing is that it has two output wires, both capable of delivering positive and negative to make a motor turn both ways.

What if you want to use a bigger motor that needs more power? Below are three circuit diagrams


How to use two analogue devices with only one analoque input?

For now it's theory, it's for a future evolution of a future project (yeah i know that's two "future")
Ok actually i'll need 3 analogue inputs (one SRF05 ultrasonic rangefinder and one 2-axis accelerometer), but the 18x picaxe chip has only two. So basically, i need to find a way to share one of the inputs. As i won't need to read the all inputs at the same time, maybe it's doable.

So two ideas came to my mind, each one with its pros and cons.

First idea : a SPDT relay.

With that, two solutions :

Transistor Confusion (again)

Greetings fellow meatbags.

Calculon is trying to hook up a pimpin motor to his Mr Basic, and has come across something very confusing with his transistor.

Here's what he's trying to do with a nte123 pulling a seperate power supply to a motor made for 3v:


He also tried it with a 2n3904. It didna work for either. According to his understanding of NPN transistors, the output from the picaxe should switch on the tran, and pull the 3v through the motor. No?

H bridges and transistors

There have been a lot of questions lately about transistors, NPN vs PNP, Bipolar or BJT vs FET and their use in "H" bridges. I had considered doing a tip/walkthrough on the subject but typing "transistor" into google gave lots of great results. Same happened when I typed in "H bridge design". I realised I would be wasting my time writing a tip/walkthrough on either subject as there is better more detailed explainations already available. So for those who are afraid to google I present these links.

LED String

Hey All,

Let me present my next round of noob question to keep you all on your toes....

I'm trying to add AmandaLDR to my next project. Two eyes in front, two on the bottom for edge detection. The problem is that digital outs and space for wires are limited, so I was hoping to combine my SuperBright LEDs into a single output if at all possible.

When I connected the anode of one LED to the cathode of the next LED, only the second LED would work. Ditto for the third of 3, etc.

1. Is that because of the forward voltage of the LEDs?

NPN vs PNP, a fundamental or just a mental difference

Like many here, I were in need of a bit of amplification of a weak signal. This signal had "low impedance", I suppose. The supplied circuit diagram shows two different ways of meeting my need.

The left circuit uses a NPN transistor. The right hand circuit uses a PNP transistor. I chose the one with PNP. Quite "arbitrarily". The BP103B is also known as FA300.