For those of you who don’t already know about the FM3 Buddha Machine, here’s the scoop:

The Buddha Machine is a small plastic box that plays meditative music composed by Christiaan Virant and Zhang Jian. (source:

The device is inspired by electronic prayer boxes, popular in China, that play back looped recordings of Buddhist prayers. Instead of prayers, the Buddha Machine plays back various ambient music loops. The duo behind FM3 have even enlisted artists to contribute material for special editions, as in the Gristleism, developed by the industrial group, Throbbing Gristle, securing the device’s status as an alternative distribution format.

Back in February of 2011, FM3 posted a tantalizing preview of a Solar Buddha Machine prototype on their blog. After over a year of waiting, and much to our dismay, we still haven’t seen any sign of the solar powered version of the device.

We love these little boxes so much that we’ve decided to take matters into our own hands and see just what we could do to power the Buddha Machine I from pure sunlight. In this post, we’ll show you not only how to run your Buddha Machine(s) from solar, but also how to modify them to charge NiMH AA cells to keep the ambient loops going all through the night.

Powering Directly from Solar

Super simple: to power the Buddha Machine directly from solar, simply connect the Voltaic Systems 1.3W Solar Panel to the DC input and position the panel in the sun.

AA NiMH Charging Modification

This part is a little more involved. First you’ll need to remove the screws from the back of the Buddha Machine’s casing.

With the screws removed, the circuit board is easily removed from the front portion of the casing. Turn it over and note the location of the power input jack.

Right next to it is a blocking diode, which makes our life easier because we don’t have to add one ourselves.

Flip the board back over. The next step is to move the green wire (negative battery connection) from its present location to the ground connection of the power jack. The power jack has a switch so that when you are running the Buddha Machine from external power, no current is sent into the batteries you may have inside. Warning: by performing this modification you may cause damage to any non rechargeable cells inside when powering from an external source (solar included).

That’s it! Close up the casing and slap some NiMH AA batteries in it. Connect the panel and you’ll be able to both play the Buddha Machine and charge the NiMH cells from solar.

How Well Does it Work?

Of course it wouldn’t be a true Voltaic Systems post without a brief look at how well the mod performs. We setup our Buddha Machine on the windowsill at the lab and took down some numbers to get an idea of how the energy is being used.

Here’s a shot of out testing setup, running the Buddha Machine directly from solar.

Directly from the 10V panel, we show that 1.4W at 11.12V is being dissipated through the Buddha Machine. Although we don’t have it pictured, a test from the bench supply at 6V indicated that the Buddha Machine’s maximum power consumption was 0.3W at .05A. What we suspect is happening is that internally, any excess voltage is being regulated, converted into waste heat internally, either through a zener diode or other voltage regulating circuit. Because the solar panel is operating at near it’s optimal voltage, a majority of that energy is wasted.

When we add the AA NiMH cells into the mix, we see the voltage drop to 3.53V and the power fall to 1.13W. The power drop is due to the panels operating below their peak power voltage. The voltage drop is a function of their internal resistance of the cells, their resting voltage, and the amount of current charging them. As the NiMH batteries are charging, they’re essentially absorbing the energy that was before turning into heat.

Sun to Runtime?

The current, shown at .32 amps while charging, gives us a clue as to how fast those cells are charging. The total capacity of the AA batteries is 2500mAh. If we’re charging at 320mA, our charge rate is a little over 0.1C, a little faster than trickle charging. What this means is that we should not charge the AA batteries for longer than 8 hours if starting from empty, even less time if we’ve only discharged them a little. If the Buddha Machine uses at most .3W and our cells are charging at .77W (including NiMH efficiency), then we can expect 1 hour of sun to give us 2.5 hours of runtime. A full charge from the 2500mAh AAs will give us about 2 days of ambient looping bliss from our Solar Buddha Machine.

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