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1066  Using Arduino / General Electronics / Re: Transistor H Bridge Help Please on: January 20, 2014, 10:49:56 pm
Right, 74HC14, I forgot about that.

Don't forget, that is two Vce drops, so still under 4V to the motor.

And actually, at 4mA source, worst-case says 0.5V drop, and at 4mA sink, about 0.25V drop. So, still not 0 to 5V. So the Vbe adds to that to create a worst-case Vce of >1V on the high side, and around 0.8V low side. Which is .... about 3V across the motor.

Remember, HFE is not exact.
1067  Using Arduino / General Electronics / Re: Transistor H Bridge Help Please on: January 20, 2014, 09:54:05 pm
MarkT, I love that design.

pegwatcher, the problem with setting them up as emitter followers is that rather than having a saturated Vce of on the order of 100mV or less, you have about 700 to 800mV of Vce. But there's more... the output of a digital pin is not 0 to 5V. It depends on how much current it must source and sink. So it might be 0.5V low, 4.5V high. Or worse. Add that to the Vce drop. So in the end, you might be driving the motor with only 3V instead of 5V, and heating up the transistors.
1068  Using Arduino / General Electronics / Re: Button to start/stop program on: January 20, 2014, 09:46:08 pm
That code will only execute inside the if statement when the button is pressed down, so of course it stops as soon as you let go.

Here is what you need, it even includes software debounce WITHOUT using delay():

http://arduino.cc/en/Tutorial/Switch

I'm not fond of the stepper library, but use what you need to. I actively hate the delay() command.
1069  Using Arduino / General Electronics / Re: Ac vs DC on: January 20, 2014, 09:37:25 pm
Quote
Does putting a bridge into this change the equation?

Without a capacitor, and with a high enough voltage that the diode forward drop is negligible, no.

With a bridge rectifier, there are two diode drops so about 1.4V is dropped out of the "bottom" of the sine wave. So the power would be less. You could get reasonably close if you take into account the power lost in the diodes.

If you add a smoothing capacitor of sufficient size so that the ripple voltage is tiny compared to the peak voltage, then you are looking at a DC voltage just under Vpk - 1.4V.
1070  Using Arduino / General Electronics / Re: What are breadboard/Arduino wire call exactly? on: January 20, 2014, 09:06:56 pm
That is stranded wire. To use it for solderless breadboards (aka protoboard), you'll need to solder on bits of solid wire as you cannot insert stranded wire into the spring contacts. Do NOT be tempted to merely tin (in other words, put some solder on) the ends of the wires. Solder gets a layer of soft corrosion that will come off onto the spring contacts in a solderless breadboard or the sockets on an Arduino and cause poor connections.

If you are soldering this in, that is the right wire to use for all but high current, high voltage, and/or high frequency signals.

It is called 22 gauge stranded hookup wire, or just 22 gauge stranded wire. Exactly what you've found here.

If you are using this for a solderless breadboard, get 22 gauge solid wire.
1071  Using Arduino / General Electronics / Re: Ac vs DC on: January 20, 2014, 09:01:48 pm
Actually, RMS is accurate to an integer number of 1/4 cycles, as long as you begin at the zero crossing or peak and end at a zero crossing or peak.

If you measure over an integer number of whole cycles, then any timing will do. As long as it is an integer number of whole cycles.

But maybe I'm being too specific...
1072  Using Arduino / General Electronics / Re: Reducing the time period a motion sensor is on from 5 secs to 0.5 secs on: January 20, 2014, 06:49:32 pm
I think the OP was hoping for a schematic, not a block diagram.

I'll try to find some time to draw something up later today.
1073  Using Arduino / Motors, Mechanics, and Power / Re: Rotating electrical contact 12 V DC 32 A on: January 20, 2014, 06:48:15 pm
Dry bearings with a large amount of current are not going to last long. Go with carbon brushes and copper pipe segments.

The original poster has never said how much of that 32A he's actually using.
1074  Using Arduino / General Electronics / Re: Reducing the time period a motion sensor is on from 5 secs to 0.5 secs on: January 20, 2014, 06:43:17 pm
Crop and resample, please. 3264x2448 pixels is -way- to big.

1075  Using Arduino / Project Guidance / Re: i want to connect six stepper motor at one arduino uno on: January 19, 2014, 11:34:07 pm
Three pins, for Step, Direction, and Enable.

Or if you only ever move one stepper at a time, never, ever needing to move more than one at a time, then you wire all the Step and Direction to the same two pins on the Arduino, and use Enable to activate the stepper you wish to move.

So 6 steppers would be 14 ports total.
1076  Using Arduino / General Electronics / Re: Reducing the time period a motion sensor is on from 5 secs to 0.5 secs on: January 19, 2014, 11:27:10 pm
What voltage is coming from the sensor to power the relay?

If 220V, then perhaps that could power a power supply that would power up a 555 timer wired as a one-shot that only triggers when the power turns on and won't retrigger until power is cycled off and back on again. A 5V relay could replace the 220V relay.
1077  Using Arduino / Installation & Troubleshooting / Re: OLD STORY: avrdude: stk500_getsync(): not in sync: resp=0x00 on: January 19, 2014, 08:39:46 pm
How will you make sure that programmer does not have a counterfeit FTDI chip?
1078  Using Arduino / General Electronics / Re: how to calculate the exact frequency of this FM transmitter? on: January 17, 2014, 08:47:06 am
I suggest that you start with something simpler.
1079  Using Arduino / Motors, Mechanics, and Power / Re: Stepper Motor Minimum Speed? on: January 17, 2014, 08:42:34 am
As someone else stated, this motor really needs a chopper driver board like the Pololu A4988 based board.
1080  Using Arduino / Motors, Mechanics, and Power / Re: Stepper Motor Minimum Speed? on: January 17, 2014, 12:40:09 am
Ugh, I hate delay().
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