Is there a way to create a boost circuit with only these components (no semiconductors or integrated circuits)?

  • Any manipulation of wires (inductors count)
  • Motors
  • Mechanical switches
  • Relays
  • Resistors
  • Potentiometers
  • Capacitors

This means no transistors or diodes. Is this possible?

Note: the second part to my original question is now here.

  • 6
    \$\begingroup\$ As regards the question look at radioremembered.org/vpwrsup.htm Some of us 'old school' will remember the vibrator power supplies \$\endgroup\$ Nov 27, 2017 at 15:13
  • 4
    \$\begingroup\$ 1. The "conservation of energy" comment is distracting and unnecessary. 2. Your question should begin with the design constraints of the competition to make it clear that this is not an X/Y problem. 3. A link to the full competition rules would help people to give more useful answers. \$\endgroup\$
    – Frosty
    Nov 27, 2017 at 15:58
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    \$\begingroup\$ "a propeller levitated vehicle is supposed to lift as much mass as possible. The rules limit battery voltage to 9v" - choose motors that produce the most lift when powered directly from the battery. Any extra circuit attempting to boost voltage will just waste power. \$\endgroup\$ Nov 27, 2017 at 16:00
  • 7
    \$\begingroup\$ Right, now we know the real constraints! In which case the boost conversion is not going to help you because the limiting factor is the internal resistance of the battery. Your best bet is to get an optimal matching of motor power to propellor speed, which is more of a mechanical engineering problem. \$\endgroup\$
    – pjc50
    Nov 27, 2017 at 16:00
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    \$\begingroup\$ Power from battery at 9v, directly into motor and prop with pitch and kv chosen to use the 9v to run at a speed which draws a large current from your battery. All a boost converter does is add weight, waste power, and change the motor effective kv. \$\endgroup\$
    – Neil_UK
    Nov 27, 2017 at 16:43

2 Answers 2


There are plenty of ways to skin this with what you have listed.

Rotary converters spring to mind, basically a DC motor coupled to a DC generator (Which is just another DC motor), WW2 technology, lots of the old aircraft radios used these.

You could also use a motor with a set of cams operating switches to build a flying cap doubler, or even do this with a relay wired as an astable (This will be kind of hard on the relay contacts).

The vibrator was a special case of an astable relay actually designed for this use case, with carefully chosen inductors you got zero current switching and surprisingly good contact life. They were popular as a source of HT for valve based car radios in the 50's.

Am I allowed to take some of the copper wire and oxidise it to get copper oxide? If so I can make a copper oxide rectifier which opens up some possibilities.

Find yourself an OLD book on electrical machines, ideally dating from about 1930, there will be examples of all kinds of cool semi mechanical ways to do the stuff we do with a few chips these days.


If you can stand the continual buzzer noise, these work.. for a while...


simulate this circuit – Schematic created using CircuitLab

Though by your definition, the bridge rectifier would be cheating... as such a capacitive doubler may be more to your liking.


simulate this circuit

Or a more classical inductive booster.


simulate this circuit

All of these would be horribly noisy though, not just audibly, but EMI too. Relay life will also be short.

  • \$\begingroup\$ These designs looks so bad. But they are still the best given the constraints. \$\endgroup\$ Nov 28, 2017 at 1:11
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    \$\begingroup\$ @HarrySvensson No kidding right... \$\endgroup\$
    – Trevor_G
    Nov 28, 2017 at 1:12

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