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mklotz
11-09-2014, 05:31 PM
In the event of a power outage, I would like to have the capability to power low voltage (e.g. 1.5, 3, 6 VDC) devices from a small 12 VDC sealed lead-acid battery. Is there a voltage regulator or similar that could be set up to do this?

George Seal
11-09-2014, 05:40 PM
Marv,
haven't seen you post in a while
Gad to see the ground is still below you

mike4
11-09-2014, 05:48 PM
Yes , i have used the regulators out of the better quality wall warts , when the transformers die just remove the regulator board ,bypass the rectifier if using DC input and there is a well regulated supply .

An example is using the 24 volt starter batteries on a machine to power your 18 volt tools , the batteries always seem to go flat before the job is finished and its getting dark.

Michael

Davidhcnc
11-09-2014, 05:53 PM
Best thing would to buy a selection of "Waterproof DC Converter 12V Step Down to 6V 3A 15W Power Supply Module New " off ebay or some other cheap source for a $2 each. One for each voltage you require.

They work well

danlb
11-09-2014, 06:20 PM
You can buy 12 volt car adapters to output just about any voltage below 12 volts. Radio shack used to sell them. I have one that plugs into the cigarette lighter a and provides from 3.3 to 27 volts. A dial sets the output voltage.

For 5 volts I just use the circuit board from a USB cigarette lighter adapter.

For other voltages I will either buy the right adapter or I will make one from an lm317 and a couple of resistors and capacitors. Literally 2 resistors and 2 capacitors. http://www.eleccircuit.com/lm338-lm350-lm317-voltage-regulator-calculator/

Keep in mind that the regulators will often use some power even if the device it powers is off, so disconnect the 12 volt supply when not needed.

Dan

danlb
11-09-2014, 06:27 PM
I almost forgot. Places like MPJA have lots of surplus parts like converters. Go to http://www.mpja.com/searchprods.asp and search for "converter" to see some examples.

mklotz
11-09-2014, 06:36 PM
Damn, you guys are quick.

Based on the advice offered so far, I managed to find these...

http://www.amazon.com/DROK-Adjustable-Regulator-Experiment-Voltmeter/dp/B00BYTEHQO/ref=sr_1_6?s=electronics&ie=UTF8&qid=1415574878&sr=1-6&keywords=dc+converter

that look as if they should do what I want and the price is less than my time is worth.

Thanks to all for the responses.

CarlByrns
11-09-2014, 08:14 PM
Hit up your local hobby shop- RC guys have all sorts of choices for converting power from 12 vdc to something else.

J Tiers
11-09-2014, 09:24 PM
A note specifically because of your use as backup power.

There are plenty of "linear" regulators, but they all waste lots of power in the step-down process. You may want to stick with "switching" type regulators because they will draw considerably less current at the input voltage than they supply at the output voltage. This is because they convert the power, not just the voltage. So the power at low volts is obviously more current than the same power is, even with losses, at the higher voltage.

Makes the battery last substantially longer. Probably 2x for a 12V to 5V converter.

The one you linked is a switching type, but may use a good bit of power in its display.... since it seems to be a variable type that the display is useful with.

mickeyf
11-09-2014, 11:24 PM
Absolutely switching rather than linear. If you don't need the display, search "Regulated Power supply" on eBay, and you'll find things like this (http://www.ebay.com/itm/DC-3-35V-to-1-25-27V-DC-Step-Down-Converter-Voltage-Regulator-Buck-Power-Supply-/131343897466?pt=LH_DefaultDomain_0&hash=item1e94b4d37a), including probably the exact voltages you need, so no need to mess with adjustments.

However, I don't think you mentioned the power requirements. You should make certain that whatever you get can supply as much current as you need.

DICKEYBIRD
11-10-2014, 09:26 AM
Last time we had a power outage I just used my cheapo Harbor Freight 12V/120V power inverter. I think it's 1000w or thereabouts. I just snagged the battery out of SWMBO's car, brought it into the shop (attached garage) and ran an extension cord into the house. We easily charged our phones and my laptop. If it happens again I'll leave the battery in the car & run the extension cord into the house, duhhh!

MotorradMike
11-10-2014, 10:02 AM
Damn, you guys are quick.

Based on the advice offered so far, I managed to find these...

http://www.amazon.com/DROK-Adjustable-Regulator-Experiment-Voltmeter/dp/B00BYTEHQO/ref=sr_1_6?s=electronics&ie=UTF8&qid=1415574878&sr=1-6&keywords=dc+converter

that look as if they should do what I want and the price is less than my time is worth.

Thanks to all for the responses.

Those look very useful!
As JT suggested, the LED display is going to be a significant load.
I think it would be relatively simple to add a switch to turn that off once adjusted.

mklotz
11-10-2014, 12:24 PM
A note specifically because of your use as backup power.

There are plenty of "linear" regulators, but they all waste lots of power in the step-down process. You may want to stick with "switching" type regulators because they will draw considerably less current at the input voltage than they supply at the output voltage. This is because they convert the power, not just the voltage. So the power at low volts is obviously more current than the same power is, even with losses, at the higher voltage.

Makes the battery last substantially longer. Probably 2x for a 12V to 5V converter.

The one you linked is a switching type, but may use a good bit of power in its display.... since it seems to be a variable type that the display is useful with.

Re the power used by the LED display...

Looking through the Amazon reviews of this product, I found this...

Smooth voltage adjustment and fairly accurate measurements. Also found a few hidden modes. If you hold the button that swaps the input or output voltages for about 2 seconds it will turn off the led display and this setting is saved if you disconnect the power. If you hold the button for about 5 secs you will enter calibration mode. Tap the button to increase the offset voltage, up to 0.5 and then it will come around to -0.5, to swap to the output voltage hold the button for about 2 second, then the green led should turn on letting you know your know calibrating the output voltage. all calibration settings are saved as well when you disconnect the power. Only uses about 20-25ma on 12v idle with the led display off.

Most of the reviewers did point out that Amazon is doing a bit of deceptive advertising. The picture shows (and thus implies that you receive) two of the units but you only receive one.

MotorradMike
11-10-2014, 05:00 PM
Re the power used by the LED display...

Looking through the Amazon reviews of this product, I found this...

Smooth voltage adjustment and fairly accurate measurements. Also found a few hidden modes. If you hold the button that swaps the input or output voltages for about 2 seconds it will turn off the led display and this setting is saved if you disconnect the power. If you hold the button for about 5 secs you will enter calibration mode. Tap the button to increase the offset voltage, up to 0.5 and then it will come around to -0.5, to swap to the output voltage hold the button for about 2 second, then the green led should turn on letting you know your know calibrating the output voltage. all calibration settings are saved as well when you disconnect the power. Only uses about 20-25ma on 12v idle with the led display off.

Most of the reviewers did point out that Amazon is doing a bit of deceptive advertising. The picture shows (and thus implies that you receive) two of the units but you only receive one.

Well that makes them even more desirable!
I think they show 2 units in order to display 2 voltages, 12.4 IN, and 5.2 OUT.
The camera is overwhelmed by the bright LEDs though so it's hard to see.
You can see the IN and OUT LEDs lit indicating what the voltmeter is measuring.