Category: Electronics

Current limiting circuit v11

More experimenting. Only 1 day left of the Multisim trial so I better make good use of it. So… It turns out a couple of those resistors arent necessary, simplifying the circuit. It still works perfectly fine. Short out R5 and the load goes to 450mA, never more.

If the physical circuit works just as fine as in the simultor, this could be quite a nice, cheap circuit to protect me when Im experimenting and hooking up jumper wires all in a mess on a breadboard. Ya never know when the next short circuit will happen.



Wind sensor

From a post on /r/Arduino I had some ideas about how to make a simple wind sensor.


Tested one of the Hall sensors I have with a neodymium magnet I took out of an old CD-ROM. The particular Hall sensor in the breakout board is a 49E501BG. At first I tried another Hall sensor but the output from that one was almost digital, useless.

When I tested it I attached the magnet to the tip of a screwdriver and moved it around in all kinds of ways around the sensor. It gave nice clear readings from 300 with the magnet at its closest to 600 with no magnet or even 800 if the reverse side of the magnet was close.

Pingpong ball would give the wind more to drag on. A dampener (more rubber bands) would be good so that the magnet doesnt move too far away even in a full storm.

Oscilloscope day

Arrival today from Amazon, a cheap (£46) USB oscilloscope. This one is either fake chinese or something, or I was lucky. All the other scopes, same model, were about £60. I havent opened the package yet, so we will see…


This is the lowest end budget version, 2 channels, 20Msps. Have to start somewhere…

Circuit optimizing day

Spent the day trying to optimize my current limiter circuit by testing different kinds of transistors in Multisim.

The one I found that seems to perform the best (according to some metrics) is BD137G which in the simulator has a voltage drop of only 0.03V. Compared to the original BD243CG which has a voltage drop of 0.09V

Here is the schematic:


China complementary order

Ordered a few more things;

  • 10x 74LS08 (Quad AND-gate)
  • 50x BC547 (common NPN-transistor)
  • 10x BD243C (heavy duty NPN-transistor)
  • Ceramic capacitor set (300 pcs)
  • 100x 3mm LED set (white, yellow, red, green and blue)

Ordering this from China was cheaper than ordering a single 74LS08 from an electronics supplier in Sweden. Sweden delivery would have taken only 1-2 days though. Chinese delivery even with a bit of upgrade in shipping is still going to take 20-30 days.

Current limiter circuit

Got it working in Multisim, an electronic circuit simulator.

Why am I working on a current limiter circuit? Well, because I quickly flubbed and burnt one of my Arduino Nanos by way of short circuit and in the future Id like to avoid losses because ordering new stuff from China is a painfully slow process.