Can you link to the code you’re running? Also, if your circuit is more complicated than just the sensor connected to the Arduino, can you show a schematic that can be viewed on mobile without kicad available?
Thanks, that’s good to know! The datasheet doesn’t seem to include the word “duty” anywhere, so I think that must have been omitted. Ostensibly that means the maximum duty cycle is unlimited, but I don’t have enough experience here to say that with any confidence.
Doing some quick math, the transistor will have a base current of 5 milliamps, which a Pi should be able to supply. At a fairly typical beta of 100, the transistor could drive the fan at up to .5 amps, which is plenty for a small fan. A MOSFET transistor is generally better suited for switching high current loads, but for this a BJT (as drawn) should be fine.
Just about any soldering iron should work. Chisel tips are better than round tips for most work. I really like J tips as well, they’ve got a range of usable surface sizes without having to change tip just by turning the iron around.
Put a piece of heat shrink tubing on one wire.
Strip the ends, and form a Western Union splice in the wires to hold them.
Set the iron to 350°C, and let it heat up. If your iron doesn’t have temperature control, it’s cheap crap and should probably just be thrown in the trash since it’ll tend to over-heat and lift pads when soldering PCBs. Continue for now, that doesn’t matter as much for soldering wires.
Then apply a tiny bit of solder to the tip of the iron so that it can make good contact, apply flux to the bit where the wires join (do NOT skip flux), touch the solder to the wires, and then touch the iron to the other side of the wires. The solder should quickly melt & flow into the joint.
Remove the solder, then remove the iron.
Let the joint cool, then slide the heat shrink up over the joint and shrink it with a heat gun.
Crimp connectors tend to be stronger and more vibration-proof than solder, but sometimes space constraints mean that soldered splices are necessary. Also crimpers are expensive, for many wire-to-wire crimp families the official crimpers are several hundred dollars.
I suggest that you give details of the iron (and tip) and solder that you are using and a close up photo of the wires that are being problematic.
The iron temperature control may be faulty and the iron just not getting to soldering temperatures. Or you may have it set too low.
The thermal mass of typical USB wires is so low that, if the solder actually melts freely at the tip end when not soldering anything, it should do so when soldering these wires.
Breadboard is a cool idea, but your first experiments will likely be super simple right?
Here’s a few thoughts.
How about some double conducting copper tape and sheets of craft paper or cardboard. (Double conducting conducts on the top as well as the sticky side so overlapping joins completes the circuit).
You can draw/plan and then route the copper sticky tape like a circuit board. Fashion basic switches from the copper tape around a cardboard flap, tape down any “flat” components like resistors.
Add some tinned leads to anything that would stick up from the board.
I often find the more tactile “MacGyver” approach is a better teaching aid as there’s no mystery behind the scenes (no hidden board wires, no pre-mounted components or connectors). Everything is built up from existing skills and experiences.
When you start to get more advanced, 80s Aussie kids grew up with:
That has a complete list of components needed for the projects in the book. Same idea as the copper tape, just with bits of wire and screws. The project in the book were all built onto a pre-drilled block of plastic with the schematic laid on top. They were fun little projects and easy enough to do - the flashers and sirens were a hit for me.
I really like the cardboard approach. Maybe I can come up with something on a plywood basis. Copper tape is a great idea. Also thanks for the link, I imagined something like this just a little bigger and sturdier and with more basic components (resistors included with the LED for example). Will save the book for later.
The standard way of looking at this is to consider a capacitor-resistor series combination going to ground. Connect a 10v (wrt ground) supply to the capacitor and the voltage across the resistor rises to +10v, then decays. Now connect that capacitor to ground and that same resistor gets -10v across it, which then decays. Whatever is connected to the capacitor “top” terminal has to be able to sink current as well as source it.
That’s what generators in simulators do - they have zero internal impedance (usually). They sink currents as well as source them.
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