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Symet
Symet Circuit 1
Symet Circuit 2, 1381 symet PCB, 1381 symet PCB layout
Symet Circuit 3
The Symmet is a very simple form of BEAM robot, it uses solar power to charge its three capacitors and at a defined voltage it will release the charge to its motor causing it to spin. It is called a Symmet due to its symmetrical nature, it is this design that allows the Symmet to 'bounce' off obstacles and go in another direction. Due to the simple nature of the Symet, this was the robot of choice for the first years to build in their first laboratory.
All symets simply run form solarengines, you can use any of the featured solarengines from the circuits section.
My Symmet, a very rough quick build.... I forgot the Asthetics part, that makes this a BEM robot! The symmet here uses the FLED (Flashing Light Emitting Diode) solarengine. The solarengine makes up the entire circuit for the robot.
A view of the single motor that runs it. I have glued some hot glue to give the shaft something to grip surfaces with.
Ok so what exactly goes on in this circuit? The solar cell creates power, the power it creates depends on its spec (power is defined as Voltage * Current). This power alone wouldn't run the motor unless it was a really good solar cell, so instead the power has to be stored in the capacitors until there is enougth to actually turn the motor.
If the motor had access to the power which we are trying to store, it would use it up even though it is not enougth to actually create movement. So we have to stop the motors from being allowed to use the power until there is enougth of it. This is where the FLED comes in the FLED will only allow current to flow when the voltage reaches the level appropriate for the FLED
being used (in this case I have used a red FLED and so the trigger voltage is 2.6V. Once this happens the circit will be complete and motor will be active, however there is no longer enougth power for the FLED to activate as it is being shared with the motor... so the circuit needs to latch on and stay on until all the stored power is used. To perform this function a transistor
is activated which bypasses the FLED and so current still flows.
21/09/05 - I have upgraded my symmet. It is now a true BEAM bot as it was once meant to be!
It now runs from a miller engine.
I have constructed it in a way that enables me to remove the solar panel and the miller engine. Solar panels are not cheap nor are 1381's. Both of these parts can be used in my Solar-Roller so I don't need to build any new circuits.
25/02/06 - Here you can see one of the symets built in the first year labs.... I have modded it to run from three solar cells in series because they were only running from a single small cell.
The symets that the students built were bought in kit form from Totalrobots, and I believe they are the same kits as the ones from Solarbotics.com.
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