Solar powered 6v dc motor

I have an excellent Polulu 6 dc motor and 2 X 7 volt solar panels that drives a music box. It will not start without shaft spin assist
works fine when started. How can it be fixed…Thanks


Please note our company name is Pololu, not “Polulu”.

We have hundreds of 6V motors. Which specific motor are you using? (Ideally, please post a link to it.) Is it able to get started if there is nothing connected to the output shaft, and can you use a scope to look at what is going on when your motor tries to start up? How much current do you expect your solar panels to be able to source?

- Patrick

The startup current of a brushed DC motor is typically 5x to 10x the no load running current, so when buying a solar panel, you need to take that startup current into account.

Many thanks for your reply Jim. I guess there is no hope to use this particular excellent motor with my solar panels unless I spin the shaft or come up with a start booster…colum

I wonder if a large, low-ESR capacitor (like the kind in the power supplies of linear audio power amps) inbetween the solar panel and motor (but on the solar panel side of the switch) would provide enough start up current?

Thanks PatrickM The panels Poly 7v 250ma 1.7w 17%5x5x3 Jameco 2245280. The v in drops to Zero on start up like locked rotor… The Pololu motor is 20D metal 6v 230 rpm max pwr 2.4 63:1 6v cb Thanks colum

Thanks jlo I agree but the v drops to zero on start so I think it would need a relay to keep the motor off while charging the cap or as some one suggested a rechargable battery 4or5 nimh…Thanks colum

Sorry for misspelling the name. I once knew a girl named Lulu thats probably why…colum

The behavior you described sounds consistent with the startup current being higher than what your solar panels can handle. As Jim explained, this can be several times higher than the no-load current draw, so I definitely would not expect your 250mA solar panels to be able to supply enough current to get the motor you have going since its no-load current is already 150mA.

- Patrick

How did you connect the solar panels? In parallel, the current doubles.

Keep in mind that solar panel current is rated for full sun at noon, and they would probably be useless to power the motor under low light situations. It is possible to employ a capacitor start system, but that requires additional electronics.

Hi Jim At one time I worked on very large motors that had internal rotary switches and smaller motors that had capacitors and relays that enabled the start circuit and then disconnected. so its bad engineering on my part but I’m going to keep trying perhaps get another panel to operate an electronic relay. colum

Hi PatrickM Thanks for your response. I wonder if you could recomend one of the mini motors the ones with the open gears and 3mm shaft that have 3 Ma draws that just maybe drive a small music box with 2 or 3 250 Ma 1.7 W solar panels
I would be totally responsible for the outcome for this experiment. RPM should be about 280 rpm …Thanks…colum

CORRECTION 3Ma draw is wrong…Thanks colum

Many of the surplus electric dc motors on eBay made by Faulhaber and Maxon are efficient enough to run solar with minimal start up amperage. I have two that when wired together, spinning one slightly causes the other to turn.
Electronic Goldmine has great 5v solar panels tat can generate over an amp of current if you like your specific motor

Thanks Jim444 for that great information
I’m determined to play my music box…colum

Since you do not have a lot of power to work with, one of our 6V Low-Power Micro Metal Gearmotors is probably your best bet. If your target speed is around 280 RPM, then you might try either the 50:1 or 30:1 gear ratio versions, but it is hard to know for sure whether either of those will work without having some estimate for how much torque the motor needs to be able to apply.

- Patrick

Thanks for your advice PatrickM…Jeff