Electrical Engineering V3 - Developers

Wouldn't be a bad idea to invest in a bench power supply, TBH. But the great thing about these things is that unless something goes horribly wrong, they should only draw as much current as they require, and no more, so 12V@5A will, at worst, result in slightly dimmer LEDs, but at best would be more than plenty to handle what you need. Could even try something that can deliver more current to test with an amp-meter (like an old ATX PSU) before you commit to something smaller/quieter for the final build, but I'd still recommend getting a bench-top power supply if you can, because they're SUPER fuckin' handy to have (and even the cheap ones aren't absolutely terrible, I hear). I even jury-rigged an old modular barrel-jack plug to use with mine so if I need an adapter to charge/power something, odds are I have the jack for it, and can set the current/voltage to whatever I need.

IRFZ44Ns are ones that i use for basically everything and they can be toggled just fine with the arduino each individual transistor would only heat up about 10°C above ambient temperature according to my calculations. You won't even need a heatsink I answered your questions already. The MOSFET i listed has a Vgs (Gate threshold voltage) of 2-4V, so 5V from the arduino can toggle it fully on. MOSFETs are voltage activated and basically draw no current at all. A raspberry is a 3.3v device and therefore it won't be able to turn them on completely. You should search for a logic level MOSFET which has a max Vgs of 3V, FDP7030BL should do.

Does anyone know how I should go about stepping down 24v PWM to 12v PWM to power a 12v fan?

Why is it PWM?

https://i.imgur.com/cHCZMjc.png Take your pick, replace lamp with motor, zener is a 1N4743, 470 ohm should be rated for 1/2W. 1uF cap is probably optional. You could of course just use a voltage divider but that would be extremely inefficient. If the PWM is software controlled and you are able to adjust it, you could just limit the max PWM to 50% which would be the same as 12V 100%.

https://i.imgur.com/48sG1JC.jpg Pbbbbt, I guess. Feel like a real dope not buying motor-drivers when I still had a fuckin' job ahahahhahahaha...

I need to shield magnetic sensors from drone motor noise. Talking about 1/1000 Nanoteslas here. Any ideas on how to do the shielding?

Put a thin piece of steel between the sensor and the motor(s). Doesn't have to be very thick at all.

Have you considered using the PRUs on the BBB for the motion control?

Maybe, if I can get around to wrapping my head around them. They'll definitely be handling serial communications if I can help it.

I'm interested in (eventually) creating a DIY home climate control system (I'm studying automation and control engineering), and I figured a good place to start would be to start logging atmospherical data both inside and outside and then try to make deductions from that. I have a Raspberry PI already which I'd like to hook up some sensors to log data to and I found this lil' board that seems pretty perfect for what I need: https://www.sparkfun.com/products/13676 however, I'm clueless as to how I'd transfer the signal data from outside to my PI, which preferably would be a distance of ~10 meters, aswell as to how I'd power the sensor in the least troublesome way (I don't have any power outlet outdoors). I've been thinking of using an ethernet cable and utilizing multiple wire pairs of sending the power and signal. Is this possible? I've read that both I2C and SPI have quite a limited distance, but since the data rate will be pretty low maybe the capacitance in the wire doesn't really matter?

I would use a low power microcontroller to collect the sensor data then send it in a burst with a transmitter module, you can power it with a 18650 and it should last a good long while, solar power may also be an option.

Finished up my dev boards https://files.facepunch.com/forum/upload/106970/081a75e5-cc06-46c3-a1bf-c4ba2b397c31/image.png I've got 8 more PCBs + components but assembling each takes me about a full working day (~200 components, ~800 solder joints), so I'll leave those until I actually need them. It's essentially an STM32F407 with all pins broken out, connected to a Micrel KSZ8463 3 ports switch. Using them to test IEEE 1588 (Precision Time Protocol) to get very precise sync of clock signals over ethernet. Besides that they also have 4 buttons and LEDs, 2 potentionmeters (not installed), a nice SMPS that runs off 5-15V (the jumper selects between USB power or the connector), USB type B connector and all the headers are on a 2.54mm grid so you can just slap some protoboard on top if wanted.

Can you make a simple OR gate with two diodes?

Yes. Try googling diode or gate

That gave me a good start, I think I'll use a ESP8266 with a battery, that way I don't need to route any cables at all thanks to the wifi. bless iot

Going to be building an 8 bit 8 function ALU. Debating whether or not to build my own adders or to just buy ICs. I already decided not to build my own multiplexer because I figured it would be too hard as a beginner to get all the wiring right.

Aw shit hey guys. Completely forgot about this thread for like a year. Anyway I'm now a slightly more knowledgeable EE student with a summer internship doing RF for a large aerospace company. Fun stuff.

I'm basing my ALU design off of a minecraft redstone design I made in sophomore year so wish me luck

Need some advice on a serial protocol to use. I'm wanting to wire up different accessories in a cosplay and have it controlled or atleast meet in a central hub. It would all be low speed stuff like <115.2kBaud. I'm thinking RS-485 as the main candidate but the terminations seem pretty power hungry (read: battery powered). I'd also prefer something easy to use and balanced/diff signalling.

Why not I2C or SPI?

When talking signals over a couple meters (In actuality, a meter from say my back to my hand, but a few meters for margin) you're dealing with a fair bit of noise pickup (at a meter you'll be picking up everything between FM radio (1/4 wavelength) and 2.4G WiFi (1/1 wavelength)) and so SNR degrades. Plus I don't want to couple enough energy to damage my transceivers. Doing I2C or SPI wouldn't be ideal for this mainly for this reason. SPI also wouldn't work as I want to minimize the number of signalling lines, half-duplex is fine.

The high-end thermostats one of my old jobs sold communicated over RS-485 differential, that should work fine. Only issues we ever had with it was if the run was too long/was too close to power wires because our bosses were cheap-skates and wouldn't use twisted-pair cable for those.

Good point, using twisted pair (Maybe spare Cat 5e?) would also be useful in just routing through clothing/fabric. Heck that's actually how I wired a friend's Umbreon hoodie I made with EL Wire. Just tonnes of Cat 5e twisted pair sewn everywhere.

How the fuck do you wire integrated circuits? You can draw a diagram like 8 and gates in a neat row, but in reality AND ICs look like: https://upload.wikimedia.org/wikipedia/commons/8/83/QUAD_2-Input_AND_GATE_IC.png How do you connect all these without the wires getting fucking everywhere? go in from the left side? Or just let the wires go all over the place and use some program to connect them with minimal overlap?

For a two layer board I'd have the inputs on the top layer and the outputs on the bottom, if you're not dealing with very fast signals layout generally doesn't matter. If you're doing it on a broadboard or similar then well, not much you can do really, color code your wires and maybe use labels as well, even a huge circuit can be made neat with some effort, redrawing the circuit with the IC layout can help a lot.

Hello, It appears that this thread is kinda sinking, but I'll just make a quick post anyway. So, being very new at PCB designs, I kinda need help reviewing a circuit I've made. Seeing as ordering electronic components and printing a board can be somewhat expensive, I'd rather have everything in order beforehand. Thing is, I'm not too sure if my design is well made and is devoid of any errors. If anyone could lend a helping hand, I would be grateful. We can take it to private message to not clog the thread too. So yeah... if you're feeling generous today, do send a PM. Thank you!