under powering a device

[Bryan Martin]

Ok I have a wireless unit that came with a wall wart which was 12V. The
unit draws around .30a running off 12V. I have successfully ran this unit
on a 7V .5a wall wart which pushed the current on the unit to around .44a.
What I am wondering is if it would damage the unit by running it off 7V vs
the existing 12V. The reason behind all this is I am wanting to run it off
solar power so the 7V .44a works out to be less than the 12V .3a.

 

[Ban]

Ok I have a wireless unit that came with a wall wart which was 12V. The
unit draws around .30a running off 12V. I have successfully ran
this unit on a 7V .5a wall wart which pushed the current on the unit
to around .44a. What I am wondering is if it would damage the unit by
running it off 7V vs the existing 12V. The reason behind all this is
I am wanting to run it off solar power so the 7V .44a works out to be
less than the 12V .3a.

Do you have a real rms-capable meter? The unit might be pulling current in
pulses. The higher current at lower voltage indicates another regulation
inside in which case the power consumption will be identical, but just your
measurement will be more off. You might also encounter less reliability with
less voltage margin. To me it seems you should look at your measurement
skills and also measure the really applied voltage at the gadget with a
second meter after the amp-meter, because there will be some drop across it.

 

[Chris]

Ok I have a wireless unit that came with a wall wart which was 12V. The
unit draws around .30a running off 12V. I have successfully ran this unit
on a 7V .5a wall wart which pushed the current on the unit to around .44a.
What I am wondering is if it would damage the unit by running it off 7V vs
the existing 12V. The reason behind all this is I am wanting to run it off
solar power so the 7V .44a works out to be less than the 12V .3a.

Hi, Bryan. Ban's right -- your measurements may be off.

I wouldn't do it. There are a lot of technical questions to consider.
If the wireless unit (wireless what?) has an internal switching voltage
regulator to supply a steady voltage to the circuit, a low input
voltage could damage the switcher. Also, the regulator may not work
properly at the lower input voltage, and the rregulator output power
going to your wireless unit might not be properly regulated. That may
mean that even if the power supply doesn't damage itself, the wireless
unit might not work well.

When you're replacing wall warts with batteries or other power
supplies, it's best as a rule of thumb to replace them with something
as close to the original wall wart as possible. Solar arrays that put
out 12VDC aren't uncommon. I'd go with one of those.

Good luck
Chris