How To Make Almost Anything Class

Lassiter's WEEK #8 Assignment

Assignment: GAME:  Dwarf Tossing

To come up with a game that utilizes one or more of the boards that Neil demonstrated in class
this weekŃchanging them in some way.  If we can further progress on our final project in some way, 
that would be good.  So my idea is to make a simple dwarf tossing game.  Dwarf tossing, though not 
very PC, was a popular sport in France for many years.  It consists of  exactly what you think.  
One takes a dwarf and tosses him as far as you can.  People win for the greatest distance tossed. 

My game will catapult a little fat doll, past a sensor that will make a sound when crossed.  
If the doll actually lands in the basket several feet opposite the catapult, a winnerÕs tune 
will play.   It will require a pair of  ultrasonic (sonar) sensors, two speakers, two 9 volt 
batteries, and 2 circuit boards.  And of course the dwarf, the basket, a catapult and  a 
support stand for the sensor and one speaker.

BOARD

First, with some prodding from above, I changed my plan from using the Norwegian ultrasonic 
sensing board to making my own board from scratch. After many hours of comparing already-designed 
boards and trying to make reasonable connections on the board, I came up with a board that combined 
both the transducer and receiver.

Pic.sch,  Pic.brd

TESTING Tx,Rx

Before doing anything, we tested the 40kHz ultrasonic transducer/receiver (Tx/Rx)  pair to see if
they worked side by side as opposed to being placed facing one another. The idea here is that my 
heart throb will detect how close people come and then trigger a heartbeat. If someone is 6 feet 
away the heart will beat, If someone is 2 feet away, the heart will beat quickly. For this week 
however, I just want to throw  an object across the transmission signal and have the receiver 
trigger a sound.   

Testing the pair  was not a simple process.  First the function generator (pos and neg ) 
has to be connected to the transducer leads. Set the function generator to 40kHz and 5VPP 
(Volts Point to Point). Next  connect the power source up such that 5V is feeding to both 
Tx and Rx. (remember to hook up both pos and neg leads) Then hook up the oscilloscope.  
Channel 1 goes to RX (hook up both pos and neg), channel 2 goes to Tx (hook up both pos and neg). 
The capacitor and the resistors in this photo are just acting as wires to handle all the connectors, 
not functioning as they normally would on a board.  

Picture

Now you need to be sure you are on the right settings, and I still canÕt quite figure how you set 
things, but once my setting are correct (want DC not AC, want the correct scale, etc.)   I should 
get a constant signal from the Tx (blue in pic) and a wave from the Rx (yellow in pic). This worked.
Then I send my hand through the signal at various distances from the pair, and in fact I do see 
significant change in the Rx wave. This is goodŃthis means I can toss dwarves or sense people coming 
into my range.  

Next step:   is to stuff the Norwegian boards and program to see what of their code will be useful 
for me and my new board.


PROGRAMMING

Manu and I looked at the programming for both the Norwegian Tx and the Rx boards.  Tx was relatively 
simple and is easy to change from their 25kHz to the 40kHz transducer/receiver pair that  I intend 
to use on Throb.    However, the RX board is a different story.  The Norwegians never established 
a good reception threshold, and when I connected their boards via wire, as they describe, I 
consistently burned out the regulator on the Transducer board.  So some deeper problem solving is 
required.

To say the least I ran out of time and had to punt to a simpler game.  In the end I made an blue 
acrylic TrebuchetŃand switched from tossing dwarves to tossing teddy bears (couldnÕt find any fat 
little dwarf dolls in the stores Š Ai yiyiyiyiy.)  And dropped the ultrasonic sensor entirely.  
And ended up putting a speaker and circuit board (hello5) with a contact connection in the top of 
a basket, such that when the bear lands in the basket, his weight will depress a folded sheet of 
paper with copper on the inside of both sides, and a connection to the battery connected to one side,
a connection to the board on the other side. Once depressed, copper hits copper, the contact is 
made and the speaker sings a little tune to signal your success.  Well thatÕs the way it was supposed
to work Š to say the least, it didnÕt really work that way.Õ

The Trebuchet was too fragile, and needed holding to catapult. The catapult opening was too small 
for the bears.  The sharp acrylic kept cutting the rubber bands so I had to use lots of gafferÕs 
tape to prevent band popping. AND the connection principal didnÕt work so well in  fact.  The bear 
didnÕt weigh enough to make the contact, and the contact eroded quickly, making it unpredictable as 
to when it would sing or no.  I think I will change to a sensor and use either a light sensor or a 
proximity sensor (capacitance?) in the future as these are more reliable.  
Pictures to comeÉ