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46  Using Arduino / Project Guidance / Soft switch on: February 17, 2013, 10:54:12 pm
I've got an ATmega328 running off 3v at 8MHz. I'm hoping to get my project powering on and off from a tactile button that will also have functions during the program. I also have limited space left on my board so I'm trying to keep the number of components low. I came up with this circuit and was hoping that it, or something similar might work. I've been trying it out (not the input part yet) and found two issues. First, it takes about 3 seconds for the arduino to set the pin high and keep it on with the pin being set high in startup. Second, it seems to stop working when I go from 3.3 to <3v from the cr3032 battery.

Using the power down function only brings me down to 0.17mA which only gives me about 40 days of "standby time." I'm hoping there's some way to get my circuit to work.
47  Using Arduino / Project Guidance / Re: best way to sense someone entering a room on: February 03, 2013, 11:31:21 pm
Yes there are some issue with PIR. It's only going to tell you if someone in front of it is moving. You can't just point it at the room and count the people. PIR would be easy if you just want to know if someone is in there or not. But to count people going in you are going to need to set it up someway just as you would a trip laser or something. a PIR sensor still isn't going to tell the difference between one or two people.

So you need to figure out these things:
-Is there more than one entry to the room?
-Is it possible for more than one person to enter it at a time, or for them to be so close that conditions don't change between them.
-Do you need to know if someone is leaving? Can they leave out the same way they came? Can someone be leaving while someone else is entering?
-Is it okay to occasionally have errors due to people leaving/entering at the same time?

Basically if you can't control all of these conditions you're going to have some trouble unless you are okay with the occasional error. If you can't get people in and out one at a time per door, you can't really tell exactly whats going on. You would either need video recognition, or enough of those pads to have a high enough resolution to actually see where people are stepping.

If you can control how people enter and leave the room, or you are ok with these errors then just get two trip lasers or two sonar sensors. The two sensors are set up so that as you walk in, you pass one, then the other. If sensor 1 detects something, then sensor 2, someone has walked in. If sensor 2 then sensor 1, someone has walked out. I wouldn't do this with PIR sensors because they detect change so they will bounce around when someone walks in front, then when someone walks away. Both send the same signal, "hey something changed.... hey something changed again, maybe someone is there, maybe not." Whereas with a sonar you can see "something is 6 ft away... ok something is 1 ft away... ok something is 6ft away again" you know that someone just walked by. Plus PIR will bounce around multiple times per change anyway, they are really only any good if you just want to know if someone is around, not anything with accuracy like this.
48  Using Arduino / Project Guidance / Re: Need to build a rotating mirror like this on: February 02, 2013, 08:23:54 pm
Anyone know of places to buy this kind of thing in NYC? I'm sick of shipping stuff from China ;p
I love the optical sensor idea... have an opaque tab pass by it once per mirror rotation, yeah? Maybe I can source one from a discarded object. I believe old mouse wheels use this... what else?
newark.com? How far of a drive is it to Jersey from where you are?
49  Using Arduino / Project Guidance / Re: 12V automotive project on: February 02, 2013, 08:18:27 pm
I made a brake light for a motorcycle. In order to detect when the brakes were being pressed I used a voltage divider. But I think If I were to do it again I would use a transistor and attach the 12v to the base with a large valued resistor and have the transistor pull the arduino pin to ground. That way if there is variation in the vehicle voltage, the pin still either sees 5v or 0v. My voltage divider would go from 3-5v depending on the motorcycles voltage. Works great but I think the transistor is a better idea. I guess the voltage divider would be good if you wanted to actually see about what the cars voltage was.
50  Using Arduino / Project Guidance / Re: RGB LED Matrix spread over 400 square feet (43 square meters) on: January 29, 2013, 04:04:49 am
(40 / 0.2)^2 = 40,000 LED's * 3 channels = 120,000 channels. On it's own that's a lot of things to control, a lot of things to wire up, a lot of things to solder, a lot of things to buy. Buy you must do all of those things for each LED.

It took me hours to wire up 15 RGB LEDs in strands like Christmas lights. Each lead: cut, strip, tin, clip, align, solder, insulate, test.... 40,000 may take a lifetime.

Edit:
Whoops i misread, but that still comes out to something like 900 LEDs. Not so out there, but we are still talking about weeks or months of work just to wire them together.
51  Using Arduino / Installation & Troubleshooting / Re: Troubleshooting sketchy uploads to breadboard on: January 27, 2013, 08:07:08 pm
That button and resistor are going into Digital pin 2 (chip pin 4) for my project, that is not the reset stuff. Pin one is connected only to the reset pin on the arduino. It is as though the reset pin were still seated in the arduino socket so it should act exactly as it does while seated in the arduino. The only difference is I am using an external 8Mhz chip so it will not upload properly while seated in the arduino.

When I say I am manually resetting it, I mean I am taking a jumper that is connected to pin 1 and physically shorting it to the ground rail. When I do this, the chip continues to operate. I am clicking my button and it is reading out on Serial right where it left off.

The cap is just for decoupling because that rail is so far away from the arduino. Removing it doesn't change anything.

edit:
I switched to a new atmega328 and it works fine now. I must've messed up the boot-loader somehow.
52  Using Arduino / Project Guidance / Re: Can I secure my code from being copied on arduino boards? on: January 27, 2013, 07:47:18 pm
The arduino board is open source. Your project is not unless you make it so. As long as you don't share your files with anyone no one can see your code. And if someone really really wanted to go to some trouble they could maybe duplicate your chip. If that is a concern then CrossRoads' suggestion of Lock Bits would be of use to you.
53  Using Arduino / Installation & Troubleshooting / Re: Troubleshooting sketchy uploads to breadboard on: January 27, 2013, 06:45:29 am
Like I said, the reset pin is wired to the reset pin on the arduino so it should act just like it does on the arduino.

But that's irrelevant because I cannot even pull it down manually. There's no problem with it being pulled up, it's running the last uploaded sketch just fine. I just can't get it to reset so it won't upload a new one.
54  Using Arduino / Installation & Troubleshooting / Re: Troubleshooting sketchy uploads to breadboard on: January 27, 2013, 04:45:58 am
I'm using an external oscillator. The problem seems to be that the reset wont pull down, not that it wont stay up. During upload I have the reset pin connected to the reset pin on the arduino so it should act exactly as it does on the board as far as I'm aware. Does anyone know why the arduino would refuse to reset when pulled directly to ground? I mean I have it completely disconnect from anything else, then I put a jumper straight to ground and it still operates normally, it wont reset.
55  Using Arduino / Installation & Troubleshooting / Re: Troubleshooting sketchy uploads to breadboard on: January 26, 2013, 10:04:11 pm
One thing I'm noticing is that while it doesn't work, I am completely unable to use the reset pin. The reset button doesn't working and it doesn't even reset when I short it to ground without any other connections. What would cause this? I think it is the problem.

Thanks.
56  Using Arduino / General Electronics / Re: Reliable digital Pot for audio on: January 26, 2013, 09:03:24 pm
Pretty expensive for just one channel. It's got the higher voltage but totally overkill on the resolution. Plus is doesn't seem to be suited for audio circuits which was one of my first issues above.

I'm afraid I might just have to figure out how to get the optoisolators working the way I need.
57  Using Arduino / General Electronics / Re: Reliable digital Pot for audio on: January 26, 2013, 08:45:07 pm
MAX5394 is 6v max, MAX5395 5.5v max.
58  Using Arduino / Installation & Troubleshooting / Troubleshooting sketchy uploads to breadboard on: January 26, 2013, 08:42:11 pm
I have my atmega328p on a breadboard with an 8Mhz chip and the arduino IDE set to Pro Mini 3.3v 8Mhz although I am powering it with 5v for uploading. Then I have the serial lines and the reset line connecting to the arduino board that has no chip seated. I also have D13 connected from the breadboard to the arduino because I found that helps. However it will work sometimes and sometimes it won't. Right now it wont. And it continues to not work even after restarting everything. I have the correct com port selected. I always get :
Quote
avrdude: stk500_getsync(): not in sync: resp=0x00

Whenever I do get it to work it's always randomly, I can't pinpoint what fixes it. Am I missing anything here? I've done this quite a few times and it's always so finicky.
59  Using Arduino / General Electronics / Re: Reliable digital Pot for audio on: January 26, 2013, 08:30:24 pm
The PGA23xx say they are for volume control but I actually need a pot, they don't mention resistance or anything. I need to control an effect pedal.
60  Using Arduino / General Electronics / Re: Reliable digital Pot for audio on: January 26, 2013, 06:09:10 pm
http://arduino.cc/forum/index.php/topic,74465.msg
This one is about the optoisolator. I never managed to find one with two outputs.

As for that chip, I know it says "audio" but I think that refers to the log taper. I actually want a linear taper. Does the word "audio" refer to the taper, or to it's ability to be used in audio applications? I mean I know it's a log taper but does that necessarily mean it is suited for audio applications?

Oh sorry, also the first issue I ran into was that my circuit uses 9v. So the digipot would need to be suited for that.
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