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166  Forum 2005-2010 (read only) / Exhibition / Re: Running high power objects on: January 20, 2011, 12:46:39 pm
Ahh, I've been doing the same kinds of experiments myself lately. To go backwards as well as forwards, you need to build an "H-Bridge". I've built 3 or 4 different designs of H-bridges in the past week. I recommend this one:
http://www.bobblick.com/techref/projects/hbridge/hbridge.html
I've got a couple of those built now. I'd recommend building it on a breadboard first, because I know I sure had a lot of trouble keeping my Bases, Collectors, and Emitters straight on perfboard until I had the circuit built on a breadboard and could just clone it onto perfboard. That H-Bridge uses maybe $5 worth of parts, and is good to something like 8amps. Point the backs of the darlington's outward, so you can put heatsinks on them if they start to produce heat, that will allow you to get a couple more amps out of them. smiley
Good luck.
167  Forum 2005-2010 (read only) / Exhibition / Re: The Arduino-Shieldbreaker on: January 20, 2011, 01:28:40 pm
Great idea. Good use for my wife's old cutting boards. smiley-wink
168  Forum 2005-2010 (read only) / Exhibition / Re: House Lights 2010 (400 RGBs) - Just in time on: December 25, 2010, 10:37:33 pm
Very impressive for sure. Did you have to use the Mega to do it, or could it have been done with a standard Arduino? 120watts.. at 5v.. Man that's some serious current draw. smiley I'd love to see more details on how the "WS2801" chip you're using works, and how you built the circuits and such.
169  Forum 2005-2010 (read only) / Exhibition / Re: Arduino Tetris on: January 01, 2011, 10:46:21 pm
I notice the Hackvision supports a Wii Nunchuck.. Does this game?
170  Forum 2005-2010 (read only) / Exhibition / Re: My digital speedometer project on: January 02, 2011, 04:35:24 am
I like it. smiley Any chance you'll share your sketch?
171  Forum 2005-2010 (read only) / Exhibition / Re: Arduino timing control for V8 engine on: January 04, 2011, 12:52:11 am
Normal dwell is anywhere from 2.5milliseconds to 4.5milliseconds. Incase you needed to know, and weren't sure. smiley If you plan to fire the coil with one of the Arduino outputs, you want to use an IGBT, put a 7.5amp fuse inline in case the code crashes, to prevent damaging your coil. 5amp might even work, but if the 5amp blows, don't panic. If the 7.5 blows, you have too much dwell. You don't need a ballast resistor with that type of setup, the ballast resistor is there to make mechanical points last longer, and is a lot of why an electronic ignition makes more power, the coil gets full voltage, so you get a hotter spark.
172  Forum 2005-2010 (read only) / Exhibition / Re: I wired up an SD Slot on: January 01, 2011, 03:24:38 pm
I doubt even a Class 1 is THAT slow.. But this was a Class 4.. I use a Class 4 as a hard drive on my SheevaPlug server. And I can VNC into that thing and nearly use it as a normal computer.
Maybe it's my resistor network that's slowing me down? I'll be ordering a WaveShield soon for another project, so I'll get a chance to see if that properly designed SD interface is any faster.
173  Forum 2005-2010 (read only) / Exhibition / Re: I wired up an SD Slot on: December 31, 2010, 02:48:56 pm
Well, I answered my question about how fast it writes to the SDCard.. This might be usable for something like a weather station, that makes one write every hour, or everytime the conditions change, but definitely not for the speed I need. Here's two log files:

The file on the right was captured from the serial port, at 38,400bps. The looptime is in Micros, each loop was 10,000 or so from the previous. Pretty much the only thing I changed in my code was to change the Serial.println's to logFile.println's, it's now about 400,000 each time around, so 40x slower, roughly.. So that's 10ms for the serial output, and 400ms to write to the SDCard.. Ouch..
either way is too slow for my needs anyways, I need 1ms resolution for the project I had in mind.
174  Forum 2005-2010 (read only) / Exhibition / Re: I wired up an SD Slot on: December 30, 2010, 10:04:54 pm
Eh.. I really didn't want to buy any parts for this. It works the way it's wired, for now. Eventually I'll be picking up a Wave shield, and a CAN-BUS shield, both of which have a properly wired SD Slot. I figure if I'm going to spend some money to do this, I'll just buy a predesigned shield.
Also, I was daydreaming about this earlier, I think it dawned on me why one of the two IO pins didn't go through the resistor network, it'd be the output from the card, there's no need to drop the voltage on that pin, since the SD card is creating the voltage, not the Arduino.. I'll change my wiring around before I finalize my circuit. smiley I still haven't heard back about the speed of this SD interface.. I looked at the cpp files in the library, I see it calibrates per card, so I imagine there is some flux in the speed.. I just hope it writes faster than 9600 bps.. smiley
175  Forum 2005-2010 (read only) / Exhibition / Re: I wired up an SD Slot on: December 30, 2010, 11:13:16 am
I've only tried the one card so far. I assume the resistors are better for the card than sending 5v to it? Is there a better way to do this? smiley
176  Forum 2005-2010 (read only) / Exhibition / I wired up an SD Slot on: December 30, 2010, 01:06:53 am
I had an old digital camera laying around with and SD Slot in it.. smiley I managed to desolder it successfully, and then wired it up to work with the new Arduino SD Library. I used these instructions:
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1206874649/8
Which I think are completely wrong, he's got the CS pin going through the resistors, but not one of the data pins.. His library also used slightly different pins than the new built in library does. I took my pictures before I got it wired up right, so don't try to follow my jumpers..





I loaded up the example Datalog sketch, and after fixing the wiring, it works like a champ.
Since I just posted pictures of it wired wrong, here's the correct way to wire and SD slot:
SDCard pin 1 to Arduino pin 4
SDCard pin 2 to Arduino pin 11 (with the resistors)
SDCard pin 5 to Arduino pin 13 (resistors)
SDCard pin 7 to Arduino pin 12 (resistors)
If you're not sure what I mean about the resistors, see the link above.. I couldn't find any example schematics for the new SD Library, but I assume it should be wired with the resistors still? Unless that guy was wrong about that too. smiley
SDCard pins 3 & 6 go to Ground
SDCard pin 4 goes to 3.3v

Worked great for me, I've got some great plans for future projects datalogging to an SD Card. Just wanted to show off my repurposing part of an old worthless digital camera (was one of those that took absolutely rancid looking VGA resolution pictures).
And if anyone knows off the top of their head, or can point me to the answer.. What speed is this thing writing to the SD Card at? SPI is Serial, right? So is it 9600, faster, slower?
177  Forum 2005-2010 (read only) / Exhibition / Re: CAN Shield on: December 28, 2010, 12:27:48 pm
Yeah, that's pretty much what I was checkin on, was to see if you were doing this for a better price than the current market options. smiley
178  Forum 2005-2010 (read only) / Exhibition / Re: CAN Shield on: December 26, 2010, 09:34:43 pm
That looks very nice. Are you going to be selling them?
179  Forum 2005-2010 (read only) / Exhibition / Re: My first project - Christmas Light Controller on: December 25, 2010, 11:35:24 am
Hmm.. Well that's cool, I'm glad it worked out for you. smiley
180  Forum 2005-2010 (read only) / Exhibition / Re: My first project - Christmas Light Controller on: December 25, 2010, 01:44:28 am
Looks like I'm done with this project for the year. I can only imagine what I'll do with the lights next year. I posted an updated video showing off the 7 segment LED, and a couple new modes I added. As well as the final revision of the sketch with all the modes working.
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