What is the stinger? In my case, this it is the mechanism that places the straw inside the glass! The straw separator mechanism (as described in the previous page) will separate a straw from the straw tank, while the stinger will rapidly accelerate the straw so that it will penetrate the coffee foam and the coffee itself. Because the stinger is fixed right under the straw separator, they could be managed as one complete group.

So, first for the stinger base:

These are the parts for the base. A U aluminum profile, a piece of plexi glass and some spacers and screws	I made two grooves to sink the screws into the 8mm plexi-glass, and using the spacers i fixed it onto the U aluminum profile	Then i took a 12mm plastic tube and with the dremel i opened a hatch

For the stinger, i wanted a powerful motor. Therefore i used a 12V DC motor with high RPM, which i had to mod the sprocket....

This is the motor that i am about to use to launch the straws	I put some hotmelt glue around the motor's pulley. I wanted to increase the friction and diameter of the pulley	Then, with the dremel, i made the pulley completely cylindrical. The external surface has also grooves (from the dremel cutter)!

It was time to put the motor and the barrel onto the base:

For the barrel, I made a V with an aluminum piece, and drilled two holes	For the motor, i had a straight aluminum piece with holes	I used these pieces to screw the barrel and the motor onto the base	The motor pulley will push the straw to accelerate in the barrel.

What's left? Oh yes, i need to fix the stinger onto the straw separator.

I drilled 2 holes onto the U aluminum profile of the stinger. I also cut a straight aluminum piece that i drilled the exact same holes on it. I will use this piece as a washer	Then i placed the stinger onto the straw separator and drilled the same holes.	I used long M4 screws to screw the stinger onto the straw separator. I used the straight aluminum piece to fix the screws on the inner perimeter of the separator tube	This is a photo taken inside the separator tube. This is how the screws are fixed inside.

Everything was ready and i could not wait to run the first complete test run! But then i realized of the hard truth... The LED-Photoresistor pair sensors did not work correct. The ambient light had a great effect on them. Although i was aware of it during design time, i did not expect such a great interference. Even small light changes would alter the sensor readings. Therefore, i went down to the design-desk again. I had to re-design the sensors to avoid external interferences. Here are the results:

This is a circuit that i published some days ago. I made this circuit to solve this problem. Testing this circuit, i discovered that it is extremely accurate! More than i will ever need of. So, i had to change the LED-photoresistor pairs with IR LED pairs:

First the IR emitting LEDs. they are connected in series. I used hot-melt to put them in position.	Then the first IR receiver diode. this is for sensing the straws. I fixed it opposite the IR LED also with hotmelt glue	Finally, the revolver alignment sensor. Fir this, i had to widen the hole a little bit, for i had an idea concerning the LED base.
This piece is a motherboard base screw from my old PC. I will use it as a base for my IR diode	With hotmelt glue, i fixed the diode onto this piece	And i put it inside the slot. I used again hotmelt glue to secure to position.

So, the straw group is now completely ready! I run several tests with full success! Time to go to the next groups: The coffee and sugar dispensers!

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