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Matt Brailsford

Member Since 21 Feb 2011
Offline Last Active Dec 06 2011 09:01 PM
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Topics I've Started

Am I reading my multimeter right?

26 November 2011 - 11:50 AM

Hi Guys, I know this probably sounds like a dumb question, but I just wanted to get clarification on whether I'm readin my multimeter right? I'm using one of these multimeters (http://www.quasarele...r-3.5-digit.htm) to try and figure out the amperage requirements of an FS-GR3C RC receiver. To do that, I have the positive lead of a 5v power supply (it's actually running off the netduino 5v supply, which in turn is running off a 9v square battery) connected to the positive lead of my multimeter, and the negative lead of the multimeter connected to the positive input of the receiver. The negative input on the receiver is then connected to the negative lead of the battery. I turn on the multimeter, and set it to the 200m A setting which gives me a reading of 0.2, which I believe is 0.2mA. (by the way, I have the positive lead on the multimeter connected to the 10A input, as for some reason I get no amperage reading on the other input of the multimeter. Blown fuse?) The reason why I am questioning this, is that I thought I'd run a test to make sure I was doing it right by checking the amperage requirements of the netduino board in the same way. Now from what I have read, the requirements of the netduino should be around 40mA, however when I measured it, it was only drawing 0.8mA according to the multimeter. So my question is, am I measuring the current correctly? if not, what am I doing wrong? and if so, how come the netduino was reportedly only pulling 0.8mA? Many thanks for your help. Matt

Help figuring out power requirements?

26 November 2011 - 11:38 AM

Hi Guys, I'm trying to figure out the power requirements for a project I'm working on, and could really do with some guidance. So right now I have the following that I need to power (along with what I could find to be each components power requirements): 1 x Netduino (5v - 40mA) 1 x Adafruits Motor Shield (5v - ?mA) 1 x Futaba S3003 servo (5v - 7.2mA) 2 x Tamiya FA-130 DC motors (1.3/3v - 660mA (1.2mA stall)) 1 x FS-GR3C RC Receiver (5v - 0.2mA?) I currently have the adafruits shield stacked on the netduino, with the servo connected to the servo 1 pins, the 2 motors connected to M3 and M4 and the RC Receiver connected to the +5v/Gnd pins on the adafruits shield. So the problem I have is that I need everything to run off a battery supply running for at least 2 hours (more would be better), and ALL to fit within an 8cm x 8cm x 8cm box. There is also the question of how I split the power supply up, as I have also read it's a bad idea to run the servo straight from the netduino power supply (which I believe the motor shield does). So could anybody offer some advice on how best what batteries to use? how many I'd need? and how to split this between the boards? Many thanks Matt

What did I do wrong?

19 November 2011 - 07:00 PM

Hi Guys, I was wondering if you could help explain what I did wrong in the following scenario? I'm a bit of a noob, so apologies if it sounds like a dumb question. So basically, I had my netduino connected to an Adafruits motor shield, which in turn was connected to 2 DC motors (2 x Tamiya FA-130 Motors). I then created a simple program to alternate the direction of the two motors continuously using this Mshield driver http://forums.netdui...-shield-driver. To make sure I had enough power, I connected a 10v - 1.2A external power supply to the netduino jack, and attached the power jumper on the motor shield. When I ran the program, the motors turned (though not as I expected) and gradually slowed down, and finally resulted in the L293D chip overheating and getting fried. I swapped the chip for the other chip on the board, and used a lower voltage, battery power supply which then worked (to some degree, it kept cutting out, which I'm pretty sure was due to not having enough power as I was only connected to 3 AA batteries). Anyways, I'm pretty sure the chip fried because I was applying either too much voltage or too many amps, but I'm not which and for what reason. Could someone explain what it is I did wrong, and what calculates I should be making to choose a suitable power supply? Many thanks Matt

Shield Recommendations

11 November 2011 - 08:17 AM

Hey Guys, I'm just about to start my first project with my newly purchased netduino and I was wondering if I could get some recommendations for appropriate shields? Ultimately I want to control 2 motors (just the cheap brushed kind) and 1 servo over wifi. After a search on the forums, their seems to be a few motor shields around, though most seem to only handle up to 2 motors, apart from the Adafruit shield. That said, I haven't seen any threads reporting to have controlled both motors and servos at the same time with the Adafruit shield. Should this be possible with a netduino? (I ask because I notice not all inputs / outputs seem to be available when used with a netduino) Wifi shield wise, there also seems to a few options, though I'm not sure which is best. I guess my question here is one of compatibility when used in conjunction with the motor shield above (ie making sure I have enough pins free etc). Any help would be appreciated. Many thanks Matt

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