Smart Guy. What?! Useless machine! Again! Hundreds, thousands of them clogging YouTube channels are not enough?
Jumbleview. Most of them made with toggle switch, this one has the rocker.
SG. So what? Everybody knows they work the same. And you already built Machine with the rocker switch . Why repeat yourself?
Jv. This one has different set of electrical components and special schematic.
SG. Really? Let us see.
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Step 1: Meet the Hero
Jv. Here is our hero.It is supercapacitor, which despite of it small size has a capacitance of 0.1 Farad. Just to comparison look at the second photo, when it is shown next to the traditional electrolytic capacitor. Despite to be of comparable size, electrolytic has capacitance of 470 Micro-Farad (200 times less)!
SG. But this electrolytic capacitor can handle voltage of 25 V versus 5.5 V for your "hero".
Jv. That's true, but anyway the difference is not that big compare to capacitance.
SG. You so proud, people may think that you are its inventor. How it is related to useless machine?
Jv. Alas, I am not the one who invented supercapacitor. But let us make the next step and I'll show you how it is related to useless machine.
Step 2: Circuit Diagrams
Jv. Here are diagrams of the machine with capacitor. Top diagram shows how it works, when machine is turned on. Switch connects motor to the battery and motor moves the arm forward; electrical current is flowing through the circuit of diode and relay, mounted in parallel to the motor. Relay is forced to close its normally opened contact. Through that contact (and small resistor) capacitor is connected to the battery and receives some charge.
SG. OK, now I see. When arm turns the switch back, motor is disconnected from the battery, but connected to the capacitor in the opposite polarity. Motor rotates backward and returns arm to its original state. Diode now stays in the opposite direction on the way of electrical current, so relay contact stays open and capacitor is disconnected from the battery. Most of the charge capacitor loses while it provides movement of the motor, the rest will dissipates on the winding of stopped motor.
Jv. Exactly. And I like the word you used: "dissipates".
Step 3: Components
Jv. Below is the list with components:
- Solarbotic GM17 gear motor.
- NEC 0.1 F 5.5 V supercapacitor.
- Schottky diode 1N5817
- Relay 5 V (NRP04-C50D,Frys electronics )
- Philmore Rocker switch. (Frys electronics)
- Resistor 5 Ohm, 0.5 W
- Four rechargeable 1.2 V batteries (any type).
In addition, there is a need in some wire, a holder for batteries, breadboard to mount elements and wire them.
SG. A classical useless machine has four main components: battery, motor, DPDT switch, and micro-switch. In your design, there are seven. You substituted one micro-switch with capacitor, relay, diode, and resistor. Does it make any sense at all?
Jv. I believe it does. But let us build the machine first then I'll explain.
Step 4: Dimenssions
Jv. Here are some dimensions for major mechanical components: arm, motor housing.
SG. Are you going to 3D-print it?
Jv. Alas I do not have 3D printer and do not posses needed skills. I made the arm from plywood and housing from wooden elements.
Step 5: Lid
Jv. Here is drawing of the lid, where everything should be mounted.
SG. Are you going to provide blueprint for the box and the detailed build instruction.
Jv. No. The box itself is just for decoration. What needs for machine to work will be mounted on the lid.
SG. Anyway that probably not needed. Unlikely somebody will want to repeat it.
Step 6: Assembling the Machine
Jv. Here is fully assembled machine. Motor housing mounted to the lid with help of two screws, switch inserted into the lid opening, breadboard and battery holder attached to the lid with Velcro.
SG. Its looks OK. Actually I expected from you something more ugly. But does it really work?.
Step 7: Running the Machine
Jv. It does work and quite reliably. As a proof here is the clip.
SG. Now I see your point. When machine is turned off, you can rotate the arm manually. That does not possible with micro-switch machine.
Jv. Right. For useless machine it is cool to fully disconnect itself from power at the end of the cycle. In other words turned off machine must be dead. But you can see clearly on the clip with classical useless machine (starting at second 19) that it is not quite true. Tester tries to lift the lid, but that release micro-switch and turns motor on. That machine is not dead, it just plays dead. This is not the case for machine presented here.
SG. Does it really important?
Jv. For me, yes. But speaking seriously I believe that useless machine has a great educational potential. What the best way to introduce school students to the science of electricity and mechanics? From that point of view more components is better then less.
SG. OK, OK, you almost persuaded me. But next time can you make something at least remotely useful?
Jv. I'll think about it.
Participated in the
Make It Move Contest 2017