Show Posts
Pages: 1 ... 891 892 [893] 894 895 ... 1169
13381  Forum 2005-2010 (read only) / Troubleshooting / Re: digitalWrite() HELP!!!! Wrong Voltage! on: May 26, 2010, 09:58:10 pm
Well the code should work fine. You problem is either with your external wiring or how you are measuring the outputs. Can you sketch out how your wiring is and how and where you are measuring your outputs?

As far as your PWM output, we would have to know how much current the motor requires and how you are wiring the output to the motor. General you can't drive motors directly from an output pin as the current limit has to be less then 40ma max.

Lefty
13382  Forum 2005-2010 (read only) / Troubleshooting / Re: Arduino Duemilanova heating up? on: May 28, 2010, 05:17:04 pm
You are driving too much current load. The servos are probably the biggest loads. Search around this forum for powering servos and you will find that most recommend using an external +5vdc power module rated at one amp per servo for best results. Also check what that laser draws for current, as there is a small limit (50ma or less) of current avalible from the 3.3vdc voltage pin.

Lefty
13383  Forum 2005-2010 (read only) / Troubleshooting / Re: Arduino triggers all pins at powerup on: May 24, 2010, 05:10:52 pm
We would probably have to see the wiring schematic you are using showing how you are driving the valves, it's possible you require pull-down resistors on your digital outputs.

Lefty
13384  Forum 2005-2010 (read only) / Troubleshooting / Re: Mega: using pins 0 and 1 with USB serial? on: May 28, 2010, 12:27:11 pm
Quote
Is there a way I can use Serial -  and pins 0&1 for digital out?
basically no. Pin 1 is used as a output pin when sending serial data to the USB port and Pin 0 is used as a input pin. Wiring anything else to pins 1 & 0 and using them both as output pins is fine except if you also use serial functions, then they will 'take over' the pin function.

So what is it that you are trying to do? The mega has tons of I/O pins avalible so it's unlikely that you want to use pins 0 &1 because your short of pins?

Lefty
13385  Forum 2005-2010 (read only) / Troubleshooting / Re: Supply power from two sources on: May 27, 2010, 01:52:40 pm
Quote
Is that right?

Quote
If this is correct, as the panel can provide more and more power (voltage is higher and more current can be provided) the battery side should draw less and less until it's not doing anything?

That's how it works. Getting multi paralleled supplies set-up initially takes a little time to adjust each power supplies output voltage so that it about equal to all the other supplies output voltage. How we did it to balance the load was to keep a volt meter on the common positive buss output (after all the diodes) and carefully adjust each supply so it it just started to raise the common voltage output and then back off a little. The idea is to start off with each trying to output some of the current. This all changes with temperature and the length of each supply to the common buss, but keeps the whole system in close enough balance so that the common buss sees little change in output voltage over time. Every couple of years during scheduled downtime we would recheck the balance and readjust as needed. Worked well for several decades before the system was replaced with a Honeywell system.

 The advantge of this type of set-up in the process control system was that there was more power supply capacity in total then the load ever required, and the failure of any one supply would not effect the commom load voltage. There would then be voltage alarm detectors on each supply to show if any one supply was off so that it would be repaired on the run.

Lefty
13386  Forum 2005-2010 (read only) / Troubleshooting / Re: Supply power from two sources on: May 27, 2010, 01:10:24 pm
Quote
Something tells me that it could be. Is there any way of using two power supplies at once on a single project to increase current, or is the only option to use them for separate voltage sources (if needed) in the same project?

Generally if you use wired diode isolation, multiple supplies will work together to be able to supply more current then any one supply can supply.

What happens is that as the PS supplying the bulk of the current sees an increased load it's output voltage will begin to sag due to it's internal impedance limit, and as it's voltage droops another supply will then have a higher output voltage then the first and it's diode will start to conduct and supply current to the load. Eventually the multiple supplies will come to a balance where the load gets it's total current demand but each supply is handling only up to it's own current limit.

We had such a design used in a large process control rack that used dozens of +5vdc, +/- 15vdc supplies and diode isolated from each other and then wired to a common DC power buss that all the loads wired to. There was probably 200amps of +5vdc flowing but each individual +5vdc supply was only rated for 20amps or so. It was a Foxboro Spec-200 control system.

Lefty
13387  Forum 2005-2010 (read only) / Troubleshooting / Re: Supply power from two sources on: May 25, 2010, 12:59:28 pm
Quote
If I have two power supplies and one can deliver 100mA and the other can provide 1000mA and I hook those both to a circuit that needs 500mA, what will each supply provide?  There's gotta be math for that  

Can't think of a simple way to do that without a lot of external feedback electronics to control the regulators.

Lefty
13388  Forum 2005-2010 (read only) / Troubleshooting / Re: Supply power from two sources on: May 25, 2010, 11:58:02 am
Well the regulators will provide their rated regulated voltage as long as the input voltage is above the drop-out voltage rating of the regulator.

 Another method might be to measure the raw voltage of the solar panel's output (via voltage divider to keep it below the 5vdc measurement limit of an Arduino) and let some program logic you write determine when you should switch voltage sources using relay or semiconductor power switching.

Lefty
13389  Forum 2005-2010 (read only) / Troubleshooting / Re: Supply power from two sources on: May 25, 2010, 10:42:10 am
Quote
That's really my question, if I hook it up to two regulators from different sources how does that react?  Thanks everyone.

The simplist method to do this is to use two diodes to form a 'or gate' for current steering. The output of each regulator would wire to the anode lead of a diode. The two cathod leads of the diodes would wire together and then wire to the Arduino external power connection. Whichever voltage source is higher would supply 100% of the current being drawn by the Arduino.

Lefty
13390  Forum 2005-2010 (read only) / Troubleshooting / Re: Stopping the power to a servo on: May 26, 2010, 10:23:47 pm
Quote
This is the servo I got...anyway to tell the max amps I need?
No, they don't spec the current draw nor is there a link to a datasheet. However it looks like a 'standard' size servo and one amp should work OK unless you heavily load the servo mechanically.

Lefty
13391  Forum 2005-2010 (read only) / Troubleshooting / Re: Stopping the power to a servo on: May 26, 2010, 12:40:49 pm
Quote
That should solve my problems right?


That really depends of the specific servo you use and how much mechanical load you have on it's output arm. Many servos draw more then an amp at peak loads.

Lefty
13392  Forum 2005-2010 (read only) / Troubleshooting / Re: Reading Hall-sensor on: May 23, 2010, 10:24:51 am
It could also be that the sensor is designed to not respond to fast changes, do you have a data sheet for the sensor?

Lefty
13393  Forum 2005-2010 (read only) / Troubleshooting / Re: voltage drop? on: May 22, 2010, 02:52:56 pm
Standard 9 volt batteries are a poor choice for powering an Arduino board. They have low current capacity and are probably the highest cost battery per MAH ratings. A DC 'wall wart' power supply (9vdc @ 1amp) would be a real cost saver over time, but don't get it at radio shack as they are vastly priced there, on line is your friend.

 If you must go with non-rechargable batteries you would be much better off using AA size batteries, using  6-8 of them in a series cell arrangment with a suitable batter holder.

Lefty
13394  Forum 2005-2010 (read only) / Troubleshooting / Re: Fried Duemilanove... on: May 14, 2010, 09:46:18 pm
Quote
Should I be worried?

No, not necessarily. It all depends on how much current you want to draw from external components wired to the Arduino. The basic Arduino board probably draws less then 75ma, so the regulator only has to dissipate around 1/2 watt for the basic board. If you try and draw 700ma of current for external loads, then it would be much better if you could find a 8 volt source. Most all linear regulators have automatic over current and over temperature protection, they just shutdown until the overload condition is removed.

Lefty
13395  Forum 2005-2010 (read only) / Troubleshooting / Re: Fried Duemilanove... on: May 09, 2010, 07:11:46 pm
Am I correct in plugging the positive into the arduino's VIN pin and the ground into the Arduino's Gnd Pin?

Yes, that will work, but it's better to utilize the external power jack as you then get the added protection of an on-baord series diode to protect from reverse polarity.
Also what is the GND pin on the other side (next to pin 13)? Just another place to ground?  Yes, it's just another ground pin
Thanks again.

Lefty
Pages: 1 ... 891 892 [893] 894 895 ... 1169