Monthly Archives: July 2013

Electronics Hardware Hacking

Lithium Battery Boost Power Supply Comparison

I purchased two boost converters or DC to DC power supplies, or whatever else people want to call them on eBay. One was a LiPower board from Sparkfun for $14.95. I assume it’s made in the US, has a battery connector and can be soldered with 0.1in pitch terminals. It’s setup for low voltage drop out at 2.6V but there is a small hack to reduce that (though I feel like you have better options if you’re trying two NiMH batteries because it has reduced current abilities from the hack.) See the sparkfun site for more details, including the link to the hardware hack. The output is a small solder jumper that comes preset to 5V but wouldn’t take but a minute to convert to 3.3V.  https://www.sparkfun.com/products/10255

I put a small load (my anticipated load of a project) of 50mA and this device measured at 85.3% efficient.

The other device I bought was a cheap-o Chinese converter that came as a two-pack from Hong Kong. It came with a USB connector and took anything 2 to 5V. I tested this with a 2.4V battery pack and it seems to cut out at just under 2V. The efficiency was measured at 77.0%… Also with a 50mA load. My input voltage was a bench power supply set to 3.7V to simulate a LiPo battery on both tests. A nicety of the Chinese “mobile booster” board was the red LED showing output power status. The LED blinks rapidly when it goes into low voltage cutout. The cheap-o board also output 5.20v which was fine for my application. I think I gave roughly $4 both boards with free shipping.

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Electronics

Cheap 5V power from that 3.7V LiPo

I currently have all projects on hold while I join a BMP085 break out board from SparkFun with a 8pin PIC into a barometer for my upcoming section hike of the PCT in September (I’m fairly certain I wouldn’t have a job nor wife if I declared I was going to through-hike). This year I’m carrying a DeLorme InReach SE stand alone two way satellite communicator so my wife can track me and send the occasional text message. They declare 100 hours of run time but my tests show that 72 hours is average. This isn’t going to cut it…I’ll likely need 1 full recharge to get me through (via USB cable). This led to my decision that the barometer is getting a larger LiPo battery and I am adding a boost converter… In my rush to get anything finished and somewhat tested I sniffed around eBay and found these 2-5V to 5V boost converters (with USB connector) at a ridiculously low price of 2.50$… It’s obviously coming from China. What a great way to spend some eBay bucks?! I can check that one off assuming these aren’t total garbage. I bought two and they claim 87% efficiency at 3.7V. I’ll check them out and post my results. Now I have to decide if I’m going to Bluetooth data to an android device or if I’ll throw an LCD on my project…I think weight will determine my choice.

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Microcontrollers

PIC-based ESR meter

My homebrew ESR meter spots a cap that is less than desirable. If anyone is interested I have my .asm code I am happy to share. The board is an Olimex prototyping development kit I got from ‘microcontrollershop’. It’s all assembler .. No C version and no desire to work on this anymore. The electrical aspects are documented in the code to some degree (enough that *I* could rebuild it…) I don’t have any plans for a kit. If you want the code you’ll have to agree that you’re building this project for yourself with no re-distribution. I don’t trust my code enough to be considered for some sort of commercial use.

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