Plastic digital caliper

This is cheapest, plastic digital caliper, costing ~$3. LR44 cell probably would be not included, so be prepared. These cells are also dirt cheap (they can be bought in bulk, 10 pieces in a blister for a $1), but these calipers are known to consume them quickly even if not in use (thus cells should probably be removed when not in use).

Why you should reconsider buying these? First, as mentioned: cell may die when you most need it. I've also noticed some kind of failure after time (random LCD segments blinking) requiring to remove cell and insert it again.

Second: accuracy is very poor, maybe not as poor as specified (+/- 0.2 mm would be not funny at all), but jaws are uneven, so results with 0.1 mm differences are frequent.

DEERC D20 drone

Cheap, sub-$50 miniature drone with 720p camera.

Controller, two batteries, two USB chargers, spare blades, blade protectors, small screwdriver and drone itself.

While battery has USB socket, it should be charged directly with USB but with dedicated charger.

One of the chargers had minor mechanical issue with PCB contacts inside of USB plug.

Measured supply current drawn by the charger at work: 0.8A.

I've scrapped edge of the PCB with a knife and then added a drop of glue inside to keep PCB flushed down.

Don't throw away screwdriver included in the set - two of body screws are placed relatively deep and regular small bits might be not able to reach it.

PAN2025B50X: 2.4GHz RF SOC chip, up to 1 Mbps, with Cortex-M0 72 MHz CPU, 29 kB FLASH, 4 kB SRAM.

Broken tooth on the motor gear. This is 8T gear with external diameter ~2.9mm on ~0.7mm shaft. I've ordered batch of similar gears on aliexpress, but it would take a while. I'm guessing someone crashed this drone, probably not using blade guards.

There is second board on the bottom side with camera connected.

 

Cheap 18650 flashlight

Cheap ($5) aluminum LED flashlight powered by 18650 LiIon cell. Marked as model 910.

Switch with rubber dome is on the bottom. There are two blinking modes and 3 constant modes with different power, it looks like it to switches to next mode with each press, but there is also some timeout after which previous mode is kept. When measured with ohmmeter this looks to be regular mechanical switch, so control electronics is in the body, probably near the LED.

Actual measured current consumption (with cell voltage = 4V):

• 850 - 950 mA in "high" mode with constant light
• 430 mA in "medium" mode with constant light
• 250 mA in "low" mode with constant light
• about 450 mA in fast blinking mode

I'm measuring 0.3 Ohm ON state resistance for this switch which is little worrying (maybe a room for improvement?), though maybe this is partly poor contact for multimeter probes, aluminum and springy element inside the cap (but for clarification this is not related to probes cable / probes itself, I'm measuring this as relative resistance).

This 18650 charging cradle is actually empty - it is just a socket with direct connection.

Suspiciously light charger. 4.2V output, red/green (when charged or LiIon cell is disconnected) LED. There is something unreliable with this LED, this might need longer testing. "4.2V +/- 0.5V" marking is very scary and it looks like it overcharges. While output voltage is 4.25V in open circuit, it raises further when cell is connected and charged. 

Suspiciously light 18650 cell. Probably not worth much, I wouldn't be even surprised if this would be fake cell with regular AA inside. Be prepared to replace it with something more reputable. There is plastic sleeve included as flashlight body is slightly wider inside than the diameter of 18650 (maybe this is also for short circuit protection?).

There is additional 3xAAA holder for alternative power.

Quite a lot of light output, here with maximum "ZOOM OUT". I believe this might be a 3W LED (current consumption confirms it). Small beam on the right is my smaller flashlight powered by single AA cell (https://commonemitter.blogspot.com/2017/12/099-mini-flashlight.html).

At maximum "ZOOM IN" lens position light beam (at focus point) is identical to LED structure.