Tuesday 2 December 2008

Under the bonnet of a Rampant Rabbit !

So two days later the large brown parcell arrives at my door, (which I sign for quickly... as the postman gives me a knowing wink) How do these guys know ? I am mean they must know the packaging from every online store or something. NIGHTMARE !. So then unpacking the stupidly large amount of packaging I eventually retreive said item. It is all packaged up in more layers of plastic that on a food product in a supermarket, and I have to liturally cut my way through to it. I now hit my first problem, NO BATTERIES, I have of course did not add them to my order and the thing requires 3AA batteries before it is gonna start. So I now have to run round the house to liberate all the AAs from my TV remote controlls etc, which now leaves me unable to change TV channels (I make a mental note to buy batteries). So I fire the thing up and see what happens.

Well for those of a nervous disposition (or have yet to understand) I shall endeavour to explain. This Rabbit comes with two motors, Motor one controls the main part of the device, and causes an interesting rotating wobbling motor to make the whole thing move. There is also a second smaller motor to control the "Rabbits Ears" which uses a variable vibration device to make the ears oscilate at high freqency. As you can see from the picture, the device has 2 control switches that enable the motors to be set at 5 diffrent speeds. These can be set indepenently and each switch controls a diffrent motor (I have removed the tops of the switches in the photo so you can see better how the sliders operate)

The next step is to have a look at what is going on underneath the bonnet of this thing....

I remove the batteries and locate some small screws which hold the top of the device together, and this should allow me to get at the circuit board. (the idea being, to put a meter on it and see what is going on) The top comes off fairly easily and I can now see the main circuit board in the device.
As you can see there are 2 slider switches (one I have removed) and these basically complete a circuit between a ground rail (the long copper strip) and 5 more copper strips (the broken copper rail). Each of these settings removes more and more resistors (you can see them, blue for the main motor, and brown for the rabbits ears) from the circuit making the motors go faster on each setting of the slider switch. Not too complicated then... sooo far.

The whole board is held in place by the little screws as well as some plastic posts in each corner, and the it is also soldered directly onto the terminal posts of the battery compartment which sticks through the plastic surround to make contact with the board.



The next step is to remove the board from its case, so we can have a closer look....

The board comes out fairly easily and by sticking a meter inline with the motors we can see just how much current each of them pulls from the battery. I enlist the help of techno geek friend, as this is going to envolve some electronical calculations and he is a bit of an expert in this field. We work out the big motor is going to need about 1amp, and the smaller one about 0.8amps. This of course is going to be far to much power than I can get out of a USB port directly. We are going to have to use some sort of isolated circuit / relay to control the main motors from the USB side, otherwise we could do some serious damage to the USB port.

Thats enough for today, am going to have to do some research and come back to it....

Will have to spend a couple of hours googling stuff and come up with a plan.

1 comment:

Anonymous said...

Yay for techno geeks! ;-)