The doctor is in

The USB Charger Doctor, that is.IMG_20141028_152728I went on a small eBay shopping spree, though it was mostly restocking some components like resistors, capacitors, and some RGB LEDs. The only interesting item in the mix was this USB Charger Doctor which reads out the voltage and current through a USB connection. I bought it because I’ve always been curious to see exactly how much current my devices were drawing. I tested the stock charger for my Nexus 7 (2012), the stock charger for my Samsung Galaxy S2 Skyrocket, and that battery pack I got from China. The results are all over the place, and I like that.
IMG_20141028_152420The voltage regulation of the two chargers and battery are not bad. It seems as though all three test subjects can sway +/-200mV with or without a load.

A bonus test was with my Powerocks 2600mAh battery. It’s of much better quality than the China battery pack in build quality, and as gives a very nice regulated 5V compared to the 5.08V (no load) output of the China battery pack.
IMG_20141028_152600 The current tests were what I was really interested in. I got some pretty fascinating notes out of it.

The picture above is my Skyrocket (phone) being charged. When I was doing this test, it would actually pull that 910mA only when the screen was on. It would drop down to around 400mA when I turned the screen off. I suspect it’s a current limit for the battery when it’s already charged to >90% which is what it was during that test. As I test it now with my phone around 70%, it draws a consistent 960mA regardless of whether the screen is on or not. The Samsung charger for my phone is rated at 1A so the charger is perfect.

As for the Nexus 7 charge test, it was pulling 910mA. I find that curious since the included charger is rated for 2A. Perhaps it’s a software limitation, or a change in the Nexus 7 hardware after the charger was already designed?

The current test for my China battery pack was the one I was most interested in because I wanted to know how much current it draws so I could use an appropriate charger to charge it. There’s no label for the input current, unlike the Powerocks battery, but it’s not like I’d put much trust in it if it was labeled anyway. Using the Doctor, I see it pulls a constant 700mA so any one of my 1A chargers would suffice.IMG_20141028_185028It was pretty neat to see what was going in with the batteries and chargers I’ve been using for years. I’ll still have to play around with it more as my tests have been pretty quick and not very practical. I would totally recommend one of these USB Charger Doctors if you’re interested in seeing what your devices are drawing. Thanks for reading!

Store Update

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My AMS11175v & 3.3v Fixed Voltage Regulator Board and my ATmega328p Breakout Board are now available on eBay! They’re currently sold in packs of 2. If there is another quantity you’re interested in or if you’d be interested in a bundle with one of each board, let me know!

New PCBs! (AMS1117 regulators & ATmega328p breakout)

I’m excited to finally have my second round of PCBs here! The designs are an AMS1117 regulator board and an ATmega328p breakout. I already have notes to share from soldering one of each to start testing them. The notes in this post are just from assembling them. I will have a separate post that goes into detail about my tests with them.IMG_20140918_193548This is how the boards were designed. They are meant to split apart easily with the tab between them. I got a little excited and went for it without scoring it first, so I destroyed one ATmega328 breakout since the weakest points in that area are the pin pads 2-4. No worries though, I got a few extras in this batch of PCBs, probably because they don’t take up the complete 5x5cm area I have to work with. I tried splitting another board by scoring both sides with a knife and they split cleanly without damage to either design.IMG_20140918_193021This is the AMS1117 board that has two fixed voltage AMS1117 voltage regulators. One produces 5v, the other produces 3.3v. It is a tight squeeze because the capacitor footprint is smaller than the actual capacitors, but it doesn’t seem like it’s an issue. On the back side is a note, written in text that’s a bit too small, that the dropout is 1.3v so you have to supply it with at least 4.6v for 3.3v or at least 6.3v for 5v. I forgot to include the drop of the diode which should be 0.7v, but most applications would probably use a 9v battery as the input to this board. It will be part of the testing, though 1.3v is the maximum dropout so results may vary between the regulators. We’ll see how the tests go.

It was fun placing the SMDs and trying to align them properly. It bugs me when my components end up in some awkward position so I feel the pressure with these small SMDs. I got to solder SMDs back in school where we used a flux pen, solder paste, and a toaster oven. I have none of those things so it’s hand soldering for me.
IMG_20140918_192836This is the ATmega328p breakout board. (The crooked oscillator is bugging me.) I really bumped my head with that terminal block for the power input. The terminal block I used on the board is 3.5mm while I’m sitting here with 5mm (0.2″) terminal blocks, which are the ones found on my Attiny85 board. It’s not a big deal as I can always go and buy them, or I can just solder wires like I did with this one.

The boards have proven to be functional, together no less. Again, full test results will be coming up shortly. Stay tuned! Thanks for reading!