BEAM solar engine oscillator

Thread Starter


Joined Sep 21, 2020
Screen-shot-2011-03-21-at-5.13.34-PM.pngScreenshot_20200906-121427.pngHere's a rather simple problem I've been hung up on for a while.

For anyone unfamiliar with the first circuit, it basically builds up a charge in an array of capacitors, then, when the FLED is triggered, the capacitors discharge through the motor in a short pulse. My intention is to replace the motor with a simple two transistor oscillator to instead make a short "beep" when the circuit is triggered.

I've tried simply substituting the second circuit for the motor with no luck. It must serve a crucial role that, as a novice, I'm unable to figure out.

I'm sure there's a solution somewhere. Anyone's help is greatly appreciated!


Joined Aug 7, 2008
What end result are you looking for? Maybe a solar operated beeper? Might use parts of BEAM, solar panel & cap for power supply, FLED & 2N3904 as a pulsing switch. On drawing, substitute your beeping circuit for R3 & LED. On bread board I used, R1 = 1k, R2 = 2.7k, FLED = white @ about 2 F / sec. piezo beeper, 2N3904 for 2N2222, & power 3 NiMH AAs. FlasheScan.jpgr flashes & beeper beeps.


Joined Dec 31, 2017
I'm sure there's a solution somewhere.
The problem is the component values shown in the schematic. Can't recall exactly which book it's from but that looks like page from a Forrest Mims notebook.
Change R2 to 330K and R1 to 4.7K. You can raise or lower the pitch by changing the value of C1. This worked on my breadboard.
A simpler solution is to use a DC beeper.
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