Looking for help on current project

reblis · 2012-05-24T12:04:12.565723+00:00

Expensive. I'm as lazy as anyone, but I looked for a power supply once at cell phone shack and laughed a little. Instead, I pulled an old computer out of a dumpster and enjoyed the free, supple 12, 5 and 3.3V supply.

However, that one you linked to is a painless option.

reblis · 1 day

How much current will each LED require? If the answer is 10mA, that's 1.2A total plus whatever the TLC5941s consume. That's not so much, but common 5V regulators usually can't supply more than 1A and 500mA is more reasonable unless you have a heatsink. If you can split everything into three isolated groups then you could have three 5V regulators. But don't try wiring the regulators in parallel. The groups actually have to be isolated somehow, but they should share the same ground.

As for powering the regulators, find a 7.5-12V transformer(preferably less than 9V) and either four diodes or a rectifier bridge that can handle 2A. You will also need a pretty big capacitor. 3300uF should do it. If you want to get fancy, throw in a ferrite ring and wind the wires between the transformer and the rectifier. Oh, and the regulators will probably want a small capacitor or two depending on how sensitive everything is.

Or, if you are feeling lazy, go salvage a computer power supply or(cringe) buy a premade 5V power supply.

renis-pinkles · 1 day

When a pin is in input mode, the chip gives it a really huge resistance of several million ohms so almost no current goes either way. That's why you don't need to add any resistors in input mode. When the pin is in output mode, the chip just opens the valve to let current flow freely(up to 40mA). In this case, you are responsible for providing the resistance.

renis-pinkles · 1 day

Yep, that's the one. Actually, it's the same datasheet as the regular Uno chip (ATmega328).

As for resistors, as the_raptor said, you really don't need them for sensing button pushes. BUT having said that, they certainly won't do any harm either. If you are experimenting with a new idea, a 330 or so resistor gives you good insurance in case you accidentally set a pin to output instead of input or some other simple mistake. The resistor would then save your chip from disaster. Here are some useful numbers:

arduino pins can handle up to 40mA, so 5V/0.04A = 125 ohms (the minimum any time you use output)

common LEDs work well around 2-30mA depending on type which translates to 166-2500 ohms (a reasonable value to test is 470)

motors, incandescent lights and relays typically use too much current for your arduino to handle. You will need a transistor and maybe an extra power supply.

roughroughrough · 1 day

Sounds like an ideal job for a peristaltic pump. Try googling that, but don't be intimidated by the absurdly expensive medical and industrial ones. I'm sure you can find or build something cheap.

bottlebrushtree · 1 day

How does a human interact with 1024 buttons less than 1.5mm in size packed onto something the size of business card cut and half? What hellish interface requires this?

noctorum · 4 days

I'll add:

diodes

a couple high current transistors for motors and other heavy stuff

alligator clip leads

some small PCBs

Soonermandan · 8 days

I'm sorry to sound pessimistic, but this is one of those situations where "too good to be true" may be applicable. They say

"Radial and some axial Electrolytic Capacitors. In various voltages and sizes. 100 quality pieces."

and similarly for everything else, but they don't actually specify what you'll be getting. You might end up with 60 axial 10V 47uF caps.

On the other hand, the prices really are awesome if you end up with something you wanted. If you like gambling, give it a try.

xb4r7x · 8 days

Here's a simple way to isolate the problem area. Completely disconnect the arduino from the relay. I mean both sides. place a resistor and LED on the leads where the relay was. Try it.

If the LED lights up, the problem is not the relay, but probably on the power supply side of the circuit. Pull out an ohm meter, unplug everything, and figure out where they are connected.

If the LED doesn't light, the problem is in the relay. The relay is a SPDT which means the 12V side has three pins. you should only be using two of those. Make sure the third is not connected to anything. Again, pull out the ohm meter and make sure everything is isolated.

xb4r7x · 8 days

Hmm.. can you give us a part number on the relay? Also, are your 12V and 5V power supplies completely separate? There are not so many things that could trigger a reset. The most likely is a temporarily reduced Vcc, which is possible if your power supplies are connected in any way, but is easily remedied with a capacitor.

CulinarilySpeaking · 9 days

Happy to help. If you run into any snags, let me know. By the way, if you also need a lot of memory, the ATmega1284P is the same package with twice as much memory. Check out the Atmel site.

arnarg · 11 days

That will work. If it does what you want it to, you don't need to change it further. If you want to make it neater and free up the processor to do other things besides checking the buttons over and over, use an interrupt. Here's how. auxiliary-character provided the most useful link, but I will explain a little

If you can free up pins 2 and 3, connect your buttons to them. These are the interrupt pins. Basically, you can set it up so that when you push a button, it interrupts whatever the processor is doing and calls a special function that you specify. Set it up like this

attachInterrupt(number, functionName, type)

number = 0 for pin 2, 1 for pin 3

functionName = the name of the special function you wrote

type = RISING (for other types see the link)

Then when the pin "rises" from low to high, it will automatically call functionName(). In that function you could put something like

active_led++;
delay(100);

note that you don't need to write "active_led = ++active_led;", just active_led++; similarly for --

You can hold down the button all you want and click the button up to 10 times a second and it will only call the function once for each click.

Chooban · 11 days

member errors? please post the errors explicitly, so we can help you debug.

Now you should be example to run this example

Hahahaha

Adult_Jordan · 11 days

well... hmm... I've never tried to do anything like this. First I would recommend browsing arduino audio projects. That would give you a better idea of what you need and what is possible. See what you can do with 4 or 8 channels before you throw too much money and effort into it.

arnarg · 12 days

Is there a reason you are avoiding interrupts? This sounds like an ideal situation for an interrupt. Set the interrupt type to RISING and then in the interrupt function put a very short delay of about 100ms for debouncing. I doubt you could hit the button fast enough to notice.

Of course, I don't know what you are trying to do or what the rest of your code looks like, so this may not be the solution you are looking for.

Adult_Jordan · 12 days

I doubt an arduino could handle 16-channel audio. For one thing, the uno only has 14 digital IO pins.

You know how stereo(2-channel audio) has left and right? Well this would have left, right, front, back, and 12 other directions. If a sound was on the left frontal channel, you would hear the sound from that direction. If you placed 16 directional microphones in a circle somewhere, it would really sound like you were there.

Adult_Jordan · 12 days

HAHA I second this. And don't forget to have all the strobes flash to blind the person at the door. Blind or cause a heart attack.

Adult_Jordan · 13 days

hmmm.. interesting pile of stuff. It doesn't look too accessible. If you looked over the circuitry carefully and did some probing, you could probably find a way to trigger the flash or adjust the timing. If you synchronized the flash, it would be one massive flash.

If you placed the speakers in a circle facing inwards and stood at the center, you could get some cool directional effects. But you would need 16-channel audio.

Lokanansi · 13 days

There are countless beginner's electronics tutorials on the web, but I'll give you some keywords to look for.

You will hear the words voltage and current everywhere.

Voltage, measured in volts, is a kind of pushing force(actually a potential) that pushes electrons around. If you have a higher voltage on one end of a wire and lower voltage on the other end, it will push electrons along the wire. Some people like to think of it as pressure, like water pressure pushing water through a hose.

The flow of electrons through the wire is called current and is measured in amperes or amps, which are basically the number of electrons passing through the wire per second. Using the water analogy, it is like the flow rate.

Now we can address your question on resistors. Resistors resist the flow of current. The higher the resistance, measured in ohms, the less current can get through. For the water analogy, imagine a really narrow pipe compared to a really fat pipe. You will fill up your bucket faster using a wide garden hose than using a little 2mm tube. The different resistors are like pipes of different widths.

This is the most important bit of math you will need for electronics: Ohm's law. It ties together voltage, current and resistance in one simple formula. Current = voltage/resistance , in other words amps=volts/ohms

For example, you are using 5V. If your instructions tell you to use a 330 ohm resistor with your LED, how much current is there? 5/330 = about 0.015 so you are using about 0.015 amps also called 15 milliamps (actually, the led reduces the voltage a little, but that is a more complicated topic)

If you instead use a 165 ohm resistor (330/2) you will have twice as much current, 30 milliamps. If you use more than about 40 milliamps from your arduino's output pins, you could destroy part of the chip, so choosing the right resistor can be very important.

As for the ground question, DC electricity always needs to go in loops. Like a model train on a track, if the track just ends somewhere the train will hit the end and stop. If you build a closed loop, it will go round and round. Similarly, if you don't connect the other end of you LED to ground, the electrons just hit the end and stop. If you connect it to ground, there will be a closed loop. Every electron that comes out of the power supply, needs to come back in the other side.

This comment is getting too long.

jan00b · 14 days

It sounds like you have a large recorded file. You will need some kind of external storage such as an SD card. If you use an arduino, this will not be a cheap project. The arduino, SD card shield or breakout board, and SD card will be the expensive parts.

Or you could use some kit like this which only requires a battery and speaker and costs about as much as an arduino uno. There are 40-second or 120-second versions. Is 2 minutes long enough? If not, google "voice recorder ic" and look for something longer. There are even cheaper options if you don't mind a little circuit design and soldering.

CulinarilySpeaking · 14 days

I totally agree that it's a great learning experience. I think any curious arduino user should try programming an AVR without the convenience of the arduino IDE. Recently I've been working on programming the unsupported ATTiny10 which actually requires me to write the code in assembly. Your understanding of the processor becomes so much deeper when you have to know all the different registers, memory structures and operations. But learning about it can sure eat up hours quickly.

CulinarilySpeaking · 14 days

Thanks for the info. I agree that 7805s are not the best, but they are certainly the most plentiful when scavenging parts from junk. And they are very easy to use. If you have a good voltage source you could get away with the 7805 and a single capacitor on the output.

Actually, I probably won't really need it as I tend to use an external 5V supply, but it's there just in case.

CulinarilySpeaking · 14 days

thanks.

CulinarilySpeaking · 14 days

True. Maybe a double arduino would be an interesting project. I'm surprised I've never seen it happen. As for me, I like the simplicity and compactness of the single chip.

CulinarilySpeaking · 14 days

None so far. I'm not sure if this distance is long for 16MHz. If anybody knows about this, I would love to hear it.

CulinarilySpeaking

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