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So far in my bots Ive been reusing the same 2 transistors that I got with my original ARDX kit.

 According to http://oomlout.co.uk/starter-kit-for-arduino-ardx-p-183.html

Im using these:-


A “NPN bipolar junction transistor used for general purpose low-power amplifying or switching applications”.

 I’m using them as switches for my motors BUT I think the power is too high for these transistors.

(At the moment I’m powering my bot with 4xAAs) and the motors often stay stuck on instead of switching on & off.

But I’ve just bought these Battery Packs to lower the power a little:-


But I need to go back for these snap-on battery connectors:-


and Im wondering which of these would be suitable for my use?



Please watch the following video & then continue down for a full explanation of what I’ve done to achieve this.

This is a quick update on where I am with my #shrimpbot improvements.


Above – you can see the 2nd bot I have made. This one has been made with a 3mm orange plastic sheet that the DT dept had lying around. My first bot was made using wood and felt a lot nicer & fitted together a lot more easily. I’m using the plastic as its Xmas & I dont have access to the laser cutter to cut more wooden chassis so Im using these plastic chassis that I had lying around.


I’m really pleased with the fact that I got the sequence working using what I call the preevolved shrimp setup. It requires just 3 components & the ATMEGA chip & even if I cant get the kids  competent enough to wire this version (unlikely I think) I should be able to put 5-6 of these together myself while the kids are completing another activity.


Below you can see the previous version which used the Arduino board & a 9v box battery with the phone charger type power connector. It also requires a separate mini breadboard for the circuit.

I’m much happier with the chip & circuit to be contained on the same breadboard. I’m also pleased at my decision to switch to 4 AA batteries & a nice cheap power case. It has clear +ive & -ive leads & Ive positioned it between the two wheels on the bottom layer of the chassis.

Below – you can see the full board. I bought some flat breadboard cables (brown & purple on the left & green & red on the right) They help keep the profile of the board down and make it much easier to avoid accidentally pulling out cables. Ive included resisters – which I dont think are 100% necessary but I fried an LED 2 days ago by not putting a resister in with it and that’s worried me enough to get me back into the habit! 🙂



I realised that I could avoid soldering, given the amount of movement the bot performs, as the cabling lodges firmly enough into the small ring terminals of the motors.Image

In the above picture you can see the battery pack & how the +ive and -ive terminals are connected to the breadboards long side rails. using the RED & BLACK cabling.

You can see in this photo how the YELLOW & WHITE cables attach to the motors.


Above, you can see the preevolved shrimp setup. It has the additional RED powerIN cable & GREEN GROUND cable which allow the current to jump from the breadboards side rails to the lines that the chip needs it on.
ImageFinally you can see a full view of the Transistors. The signals coming from pins 13 & 11 (LEFT to RIGHT down the BROWN & PURPLE cables are switching the power on & off to the motors through the Transistors. The current is travelling UP the photo, starting on the bottom rail and travelling along the short RED cables before meeting the resisters which help the current jump the gap in the middle of the board. The current then travels up the rails to the LEFTmost side of the Transistor. It cannot pass unless it is receiving a signal from the chip (coming along the BROWN & PURPLE) cables. The current then travels back down the board until it meets YELLOW cables which are power going IN to the motors. The current then returns to the board via the WHITE cables and back along the board (to the LEFT) to the negative terminal on the battery pack.