syntaxrigger posted:

I was just curious how others managed the expense of electronic components and if there was something I was missing about keeping the cost down.

Dominoes posted:

Given I'm using another SPI hardware piece on the board, Is is OK to put this on the same SPI device, or do I need to use a diff/dedicated one?

Foxfire_ posted:

Depends on what you want to do.

Types of storage:
- SRAM: Very fast. Won't hold values without power
- DRAM: Fast. Only holds values for small times even with power. Used with a controller that is constantly rereading and refreshing data. (This is the kind that is the main memory on a PC)
- EEPROM: Slow. Doesn't need power. Limited number of writes.
- NOR flash: Slow reads, very slow writes. Doesn't need power.
- NAND flash: Like NOR flash, but all reads/writes/erases happen on enormous blocks instead of bytes. Also needs ECC because bit errors are normal and frequent.
- Battery Backed RAM: Take a SRAM and a battery, add some circuitry to switch the power source to the battery when main power goes away. Holds values as long as battery lasts
- nvRAM: Take a SRAM, some flash, and a capacitor, add some circuitry to copy flash->SRAM on powerup and SRAM->flash on loss of main power using capacitor power.
- MRAM/FERAM/ReRAM: Various fancy technologies for fast byte-addressable memories that don't need power to hold values. Typically looks like a SRAM, but the values magically don't go away.

Things you are maybe confused about?
- DMA = Direct Memory Access = a peripheral is reading/writing to memory directly without going through the CPU. Like an ADC could be independently saving samples into a RAM buffer for the CPU to look at later instead of the CPU having to read each sample as it happens. Not directly related to nonvolatile storage.

Things you already have inside the microcontroller (probably, I am going off of what's in a STM32F7 because that's what I use at work):
- A section of RAM that can be powered from an external battery. If you supply battery and turn it in, it will appear as a region of memory that holds its values across power cycles. It is as fast as other RAM, it is not big, and goes away when the battery does. A reasonable sized coin cell can run this for a few years. Look in the power controller section of the reference manual.
- A whole bunch of NOR flash memory. This is what is holding the program code its running from. You can also read and write data to here at runtime. Look in the embedded flash controller section of the reference manual

Ways to attach an external storage chip on a STM32:
- I2C/SPI: Access it as a generic serial device. This is slow and only the CPU will be able to access it (no DMA), but that's fine for lots of stuff
- Flexible Memory Controller: This can interface to a bunch of different memory types. You configure it with timings, bus widths, what enables should go, etc... and it implements read/writes to some address range as external memory accesses.
- QuadSPI controller: Similar to the generic SPI controllers, but supports multiple data bits per clock and map address ranges into SPI acceses.

Forseti posted:

Same device but it needs its own chip select line. Also if you are asserting the CS by tying low/high instead of an IO line for whatever else is on the SPI peripheral that's not gonna work.

Dominoes posted:

Awesome; thank you for the exceptional, detailed breakdown. Looks like I had multiple misunderstandings.

Awesome. I'm still a bit fuzzy on CS, but it seems like it can be any properly-configured GPIO pin. My WIP (untested) code has the CS pin as a push_pull_output.

ante posted:

Where do you live, out of curiousity?


That's a distinction that I have vaguely heard from people in other countries, but doesn't exist in Canada as far as I can tell.

poeticoddity posted:

The electrolytic capacitor on that board labeled C9 is tilted at an angle.
Normally, I'd ignore that, since it's often done intentionally to reduce the standoff height of components so you can use a tighter enclosure.
In this case, all of the other electrolytic capacitors are 90 degrees to the board and several of them are bigger (specifically taller) caps.

So I'll ask the dumb question: Is there any visible damage to that cap on the underside or to its connections?
Once in a blue moon I've run into caps that got handled too roughly and a lead came out or dislodged a cold-soldered joint.

Also, there's one IC in a socket. Is that firmly seated?

Stack Machine posted:

One piece of advice that has proven true time again for me is the 0th commandment: thou shalt check thine power supply. Your ICs will all have datasheets that will tell you which pins are supplies. You can check their DC values and AC values with a multimeter. Probing on that board while it's running is it's own though. Find a way to probe it without touching it while it's plugged in if you can or use an isolation transformer if by some chance you have one. If the DC value is reasonable and the AC value is 0 your power supply is OK and you're in for suffering. If the AC value is high start checking caps. If the DC value is 0 something in the supply is dead.

"But it powers up" you say. There is likely more than one supply voltage on this board. It's possible only one has failed.

Gromit posted:

Yeah, the leds power up and the PCB makes some whiny noises from somewhere near that coil, but nothing I would say was a stand-out problem (unless those things should be silent?) I'll try and check the voltages coming out of the supply and see if they are okay.

Granite Octopus posted:

If you're serious about keeping costs down and doing dumb little projects, I'd suggest scavenging.

Printers are a constant feature on footpaths around here, and I grab them whenever I can. A great source of motors, gears, wire, springs, sensors etc.

Need a raspberry PI? Any old computer with a parallel port will do the same thing. It can be hard to know when you're hoarding junk vs collecting specialist hobby resources but if you have a bit of space it's never been a better time to collect e-waste.

Personally I don't really like buying new stuff just to do a project, both from an economical and environmental standpoint, so scavenging makes much of my stupid bullshit possible.

Forseti posted:

I don't know that it is working in the video though? I mean he shows a square wave that isn't square half the time and it's "working" because it changes when he blows on it which is pretty much random noise to begin with.

I haven't really played a ton with i2s myself but it looks like it doesn't have any error detection and different impedance between various lines can cause issues:


What was the original goal? Just to read the ESP32's internal ADC and output that value on the i2s bus? I think it might be best to start simple, so like maybe hook a potentiometer up to the ADC input and see if you get the i2s interface sending the same value over and over first, then go from there.

syntaxrigger posted:

I love the idea of upcycling old electronics into stupid robots/electronic projects but I have a feeling the required knowledge to do effectively is leagues away. That being said I LOVE this guys videos! He also will reverse engineer stuff every so often and that skill feels immensely useful.

https://www.youtube.com/watch?v=pi3EVvdaPuw

babyeatingpsychopath posted:

I came here to post https://www.youtube.com/watch?v=vq968AFgPhg, which I got from Hackaday today.

Ambrose Burnside posted:

ohhh that’s smart, i like this, and i have access to a cricut so i could roll my own from CAD files p painlessly. prolly not suited to anything other than low-power circuits and i bet typical soldering temps ruin the adhesive, but still, dang

babyeatingpsychopath posted:

If you like him, you'll love https://www.youtube.com/user/bigclivedotcom . Big Clive has an amazing Manx accent and wonderful reverse-engineering skills.


I came here to post https://www.youtube.com/watch?v=vq968AFgPhg, which I got from Hackaday today. This is absolutely ram-packed full of good info. The middle third goes through so many good things so fast it's worth watching over and over until they stick.

ante posted:

If solder is coming up with the tip, your joint isn't hot enough. Solder follows the heat - look up soldering videos on YouTube, and you'll see that the iron only gets dabbed with solder briefly to allow faster heat transfer, and then the majority of solder gets jammed into the joint itself.

That Works posted:

I naively thought that a single relay could just make the actuator go down and then take the signal off of it and then it would go the other way.

Just wiring the actuator directly to the battery does this:

Blue wire (-) Brown wire (+) = actuator extends
Blue wire (+) Brown wire (-) = actuator contracts

So I can't just turn relay on and off to change directions. I guess I would need 2 relays. I think maybe they could work if wired like so?



I apologize for my crude diagram. I've never had a circuits course and have only been reading about this stuff for like 2 weeks off and on.

Shame Boy posted:

One thing I was never able to pick up from videos and had to learn was that it's okay to put a bit of down-force on the iron, your goal is to make good thermal contact between the iron and the joint so it dumps in enough heat quickly enough. I mean not enough that you're wildly bending the board but it's fine to hold it down nice and firm.

Forseti posted:

For soldering I use a pretty big chisel tip as my go to (I think it's 2.4mm but I don't remember off the top of my head).

If the last soldering you did was 30 years ago I'd guess you probably used lead solder. If you just grab the first solder you see now it's probably lead-free, which needs more heat and usually just isn't as easy to get a good joint with, although I wouldn't say it's horrible to work with personally. But lead is definitely easier.

That Works posted:

mobby_6kl posted:

I think I worked out the biggest software challenges in my project, definitely a lot of stuff to clean up but the important bits are working, more or less. So I think I'm ready to make the first PCB, probably a DIY one first but still I need to start designing it.

What's the recommended software nowadays? I might actually be able to get the educational Altium through school (even though I never studied EE) by pulling some strings, but I've no idea if it'll actually be better for a noob or just have a ton of crap don't need. I have no prior experience so I could try anything really.

babyeatingpsychopath posted:

The standard way to do a relay-controlled bridge is one DPDT relay, and one SPST relay. The DPDT is "direction" and SPST is "enable." The relay module has the ability to use separate power for your relays and optoisolators via a jumper pin.

I really like this relay module. The SSRs turn on just fine with 3.3V. You can make a full h-bridge with these.

Sagebrush posted:

You have run into a fundamental problem of DC motor control that is fixed with something called an H-bridge.

https://en.wikipedia.org/wiki/H-bridge

You have nearly designed one yourself, and the half-bridge thing you've got drawn up could theoretically work. But the problem with your design (if I'm reading it correctly) is that there are only two switches and there's no neutral position. So you risk shorting everything out if the timing isn't exactly simultaneous, which is impossible to guarantee with mechanical switches. Actually, now that I look at it more closely, I think you'll be fine -- the intermediate position will just connect both sides of the load to the same voltage so nothing should happen. What you have will work.

The good news is that H-bridge chips are super cheap (search Amazon, there will be tons of modules), or if you want to build one yourself, they aren't difficult to put together.

Thermopyle posted:

When I was a kid I played this game on my Tandy CoCo that IIRC you moved from room to room à la Zelda dungeons and slapped together electronics components to build circuits. My memories of it are pretty fuzzy, but I remember enjoying it.

Does anyone have any idea what I'm talking about?

Forseti posted:

Four AAs is probably the easiest way to do that. That only gives you around 1200mAh though. LiPos can't fly and are annoyingly expensive to ship as a result. Never used LiFePo batteries. LiPos can be harvested from a USB power bank, they're way cheaper than just bare LiPos everywhere I've looked.

Sagebrush posted:

You have run into a fundamental problem of DC motor control that is fixed with something called an H-bridge.

https://en.wikipedia.org/wiki/H-bridge

You have nearly designed one yourself, and the half-bridge thing you've got drawn up could theoretically work. But the problem with your design (if I'm reading it correctly) is that there are only two switches and there's no neutral position. So you risk shorting everything out if the timing isn't exactly simultaneous, which is impossible to guarantee with mechanical switches. Actually, now that I look at it more closely, I think you'll be fine -- the intermediate position will just connect both sides of the load to the same voltage so nothing should happen. What you have will work.

The good news is that H-bridge chips are super cheap (search Amazon, there will be tons of modules), or if you want to build one yourself, they aren't difficult to put together.