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lainchan archive - /diy/ - 1806

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figured this should go here, better than anywhere else. I'm getting a little starter pack of electrical components from eBay soon: resistors, potentiometers, LEDs, a breadboard, an arduino, etc. there are lots of cool projects online that I've been aching to try out. recently my FM transmitter I used for listening to music in my car gave up the ghost so now I have that to salvage components from. the AAA battery case and aux cord are of particular interest to me.

I thought that, judging by another project I saw done with a raspberry pi zero, I could connect a wire to one of the pins on an arduino (transmit, I'm assuming?) as an antenna, and do a little breadboard circuitry to makethe aux cable usable as input. no idea if it would work, though, or the complexity of the program I'd have to write.

are any lainons here electrical engineers? what are some projects you've made or are working on? have you ever popped something open and added something of your own to the circuit board? I'll provide the link to the bundle I'm buying, if anyone wants it or wants to recommend a better one to me.


I'm an EE student right now. I don't know the pin diagram or the features arduino, but to do any EE stuff you need some sort of measuring equipment, and the small embedded boards A/D converter won't cut it. You should look around you for some hacker spaces that would have waveform generators ect so you don't have to buy them. They can be expensive. Also do you have a link to what you are talking about with the pi/arduino because you aren't making a whole lot of sense. I can provide some links to my professors website with lecture notes on electronics and embedded programing if you want.


Seconding this as another EE student, though I'm only at the sophomore level. I'm just as confused about what you're trying to do, a diagram of some sort might help.

The basic ADC for the arduino is only accurate to 8 bits, so you won't be able to do anything fancy with it. If you just want to see if you can get a signal, though, it will work fine, I was able to play around with really lo-fi audio on my Arduino once. You will definitely need a preamp to bring the signal up to 5V peak, otherwise you won't be able to do anything with it.

If you're looking to do radio stuff like transmitting and receiving data you'll need to learn a bit about amplifiers and will probably want to build a simple radio first. Just look up AM or FM radio kits and schematics. I can't speak from experience there though, I've mostly messed around with audio filters and op-amps at low voltages.

My soldering iron (cursed piece of shit from china) broke a while back, so I haven't been able to get back into playing with electronics much. I was working on building a simple op-amp based mixer when it broke, so I'll probably pick back up on that once I have the money.



So it's just a software-based FM radio. I don't see why it wouldn't work, but I don't know about the software involved. It shouldn't be hard to port the RPi code over to arduino if you're looking to do exactly the same thing. Keep in mind the transmitter is just a plain wire coming off of the microcontroller without any filters or amplifiers or anything so you will likely have problems with noise and transmission range.


As a radio amateur and electronics hobbyist, please don't try to build a based RPi/Arduino transmitter (without using a filter, anyway). They are only barely capable of it, creating large amounts of interference for other people due to using square wave carriers.

Take a look at the little one transistor FM transmitter circuits; they'll both sound better and be more efficient in their use of RF energy.


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This, a small analog circuit will work just fine if you can find a variable capacitor and don't mind spending some time in order to tune it.
Arduino has a clock frequency of 20Mhz i guess, so there's no way you can broadcast FM with it, you coud use AM, but still, arduino libraries and functions are very inefficient, and you won't get anything out of it unless you spend some days or weeks researching about code optimization. Definetely not a good project to start with.

If your car has a cassete player you can use an ectromagnet to transmit the music from your headphone jack to the sensor, I think this method doesn't needs additional power.

ElectronicE student here.
>what are some projects you've made or are working on? Currently working on a capacitor charger
>have you ever popped something open and added something of your own to the circuit board? Yes, a 433Mhz receiver inside my router which opens a small relay, cutting the power and restarting it so my roomate stops playing LOL at 3 in the morning.


>wireless router kill switch
Thanks, this just reminded me I need to set up something else similar for myself, video games kill my productivity and grades.


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Here's the end result, I welded the thing shut again with the soldering iron tip. I added an LM567 to the module so it won't trigger randomly, only at a particular frequency within the 433MHz carrier wave.


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Just realized that the router works with 15 volts, and this PSU is 12.3, just fuck my shit up.
The router probably has an 7812 voltage regulator, so I'll have to short it to make this work.


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Not sure if this is the right place to ask, but here I go:

I'm trying to make a watering system, but I'm still very much a beginner on this stuff, so here's a stupid question: How do I "transform" (???) the 5V output from the Arduino to 24V for a solenoid valve? Or is there another, better way to do this? I'm trying to keep it cheap.


1. It's called DC-DC transformer and there are plenty of kits/modules for that.
2. You can feed solenoid from other source that got 24V (auto acumulator charger, for example) but use 5V from arduino as an electric switch for that higher voltage solenoid source. You can use a thing called relay for switch, or a transistor setup. I might be wrong about transistor though.


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There are several choices to do so, I will suggest the following.

1. Get a dual supply 5/24V Supply brick: They are cheap, available and save you a lot of trouble. Getting the right supply in the first place cuts down the complexity of your build and costs less when accounting for time and money.
Using a switch mode DC/DC converter to boost up 5V from presumably the source the Arduino uses won't be as efficient. Another thing why it's backward to do so is that the 5V supply will be the bottleneck of the whole setup, meaning it cannot necessarily supply the power drawn by the solenoid over the dc/dc converter.
When building projects using a battery supply this is another story. There you might go with such an option. On the other hand, what portable project needs 24V as a supply rail.

You use the 5V/GND lines naturally to power your controller, easy enough.

2. As >>1898 mentioned earlier, a relay rated between 5V and 24V on the solenoid will be your best bet. Make also sure you get a model of the NO variety, meaning it's normally open. Another specification to consider is the maximum voltage and current rating of the switching side of the relay.

I was going to post an elaborate text on how to drive a relay properly, but who the fuck cares am I right?


Thanks guys, I'll be getting a couple of relayers to try it out soon. I already have some solenoid valves and if it all works right I'll get that arduino.


God, I meant realys.


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I'm planning to control a strip of 12v LED lights with a NodeMCU, and would like to read an elaborate text on how to drive a relay properly pls lain!

It's my first foray into electronics and embedded things, but the NodeMCU seems like a sweet bit of kit - it's basically like an arduino with built-in wifi and a comfy lua interpreter, going for about $5 on ebay.


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Well I gotta head off to my 7$/h mandatory internship at a faceless corporation in a few hours and got other things to do now.

I'll post later, promise.

Meanwhile you could tell a bit more on the LED strip and why you'd use relays.
Just to throw it out there, using a proper mosfet like the IRFZ44N to drive those will be infinitively better.
It's more efficient, but most important of all you can dim the thing in software easily afterwards.



You're looking at an esp8266 dev board then, I'm assuming that one has a ftdi driver included for easier programming.

Don't bother with the dev board, just get a generic esp8266 it's a little harder to develop for but you can get one for like 3$. I'm using some now for a sensor network for a visualization. I can share some of my research on the chip if you'd like.



Also I wouldn't advise writing the code in Lua with Node MCU, it's much easier to dev with C and C++ there's an open source add on for the arduino IDE for that.


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It's a 3528 led strip, looks quite simple to control although I'm a little unsure how to vary the brightness.

I was thinking of relays or transistors to get the 5v outputs from the chip to regulate the 12v draw of the LEDs, but I've never done this sort of thing before so that could be way out.
Any advice or introductory resources greatly appreciated.

Also, while I may play with C some time in the future, for now I'll be sticking with Lua since I know it already and there are nice libraries for the NodeMCU.


I had assumed that transistors were either on or off; having read that they can vary that's clearly the way to go.

Would still be interested in reading about relays or any other suggested reading though.


This was one of my teachers. Learn up.



Oh soykaf I found this site years ago when it was still active. Cool to see its a thing again.


Generally, most electronics use switching dc to dc converts so the 7812 would be a pretty rare find.

you know you might just try 12V to it anyway, sometime the circuit may work a little under voltage.



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we are working on MGC3030 Near field detector device for detecting hand gestures for a motion controlled tetris demonstrator apparatus at our college.

Anyone here have experience and some free time to talk about this? maybe on the IRC?

Any help is appreciated, if you like, we can include you in the list of contributors. or you can remain anonymous.

We need help designing an input electrode for the chip described in the below literature. I figure this is relevant to here, and may be giving you something to play with lains.


Another Laingineer.


bump for interest.


After the psu wall wart (the dc to dc converter) some times there is a linear regulator on the circuit board of the device to remove most of the noise, at least from what I've seen.


Bumping for interest.