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541  Using Arduino / Programming Questions / Re: Possible use of function. on: August 05, 2014, 03:03:06 am
in many of my test projects the switches are very poor - often no more than touching two pieces of wire.

It wouldn't surprise me if touching two wires together is actually less bouncy than a crap switch. If one pushed them together firmly enough there will likely be only one contact counted. Otoh when I tested one of these, I was consistently getting  2 for 1 and decided to use the bounce2 library.
542  Using Arduino / Motors, Mechanics, and Power / Re: Arduino + servos multiples on: August 05, 2014, 02:33:51 am
And here's a pic of what Robin's saying.

Conventional forum wisdom is to allow 1A per servo.....
543  Community / Website and Forum / Re: SPAM alert. on: August 05, 2014, 12:30:28 am
She's not only a member here, but brand new: registered 2 hours ago and no posts.
544  Using Arduino / Motors, Mechanics, and Power / Re: Help with relay on: August 04, 2014, 10:17:15 pm
But with the opto isolator, the coil current isn't through the i/o pin, it's across the isolator's transistor c-e, and presumably they sized the isolator to cater for that.

The current on the i/o pin is that through the isolator's led. With a current limiting resistor, that can be as low as you want it, provided the the led still fires the base of the transistor.

EDIT: Attached pic is my take on how this thing works.... R1 limits the Arduino i/o current to the isolator led.

My test would be to lose the Arduino for a minute or two, put 5V on the board input and ground to power the coil, and put 5V through a resistor and an ammeter to the isolator LED and listen for the relay to operate.
545  Using Arduino / Project Guidance / Re: read pot help wanted on: August 04, 2014, 09:50:26 am
Quote
Log or linear, if correctly matched and wired, it is going to read zero or close to it at one end of the travel, and 1023 or close to it at the other end of the travel.
True, but not half '512' in the center of a audio-taper potentiometer.

What it reads halfway along is totally irrelevant to this discussion. The OP says it's reading 1023 1/10th of the way in: that shouldn't happen with a linear or an audio pot, so it seems something is amiss here.

Once it's reading 0-ish at one end, and 1023-ish at the other, then we can worry about the (non-) linearity of the case.
546  Using Arduino / Project Guidance / Re: Trigger laser (or break a beam) without anything on the other side on: August 04, 2014, 05:11:37 am
And of course there's also Passive Infra Red which doesn't need a receiver on the far side or a reflector over there and a receiver over here. Might be worth a look, at least.....
547  Using Arduino / Programming Questions / Re: Store multiple data to EEPROM on: August 04, 2014, 04:45:06 am
And by the way use lowByte and highByte to do the splitting up before saving, and then word later on after you read them back and stick them back together again.
548  Using Arduino / Project Guidance / Re: SwitchCase (Question) on: August 04, 2014, 03:55:15 am
When I say triplicate, don't take me too literally: remember to adjust the pin numbers and variable names  smiley-grin
549  Using Arduino / Motors, Mechanics, and Power / Re: Help with relay on: August 04, 2014, 03:51:22 am
Quote
But it says it's opto-isolated, and the LEDs in the isolators won't want that much current:
I would tend to agree but that is not whet the specification says.

There was a poster the other day asking why his USB cable was getting hot and he claimed that the optos on his device needed 60mA.

Yep in the absence of a datasheet, it's pure (possibly expensive) speculation....
550  Using Arduino / Motors, Mechanics, and Power / Re: Help with relay on: August 04, 2014, 03:49:55 am
Yeah use an external supply for Vcc.

Can you see the traces on the PCB?- maybe you can try figure it out by some detective work.

Does it have a maker's model number to Google a datasheet?
551  Using Arduino / Project Guidance / Re: SwitchCase (Question) on: August 04, 2014, 03:47:22 am
Right then you should look at this example and just triplicate the part where it's looking at the buttons and when any button is LOW (LOW means pushed, that's the logic with pullups) do the stuff you need for that button.
552  Using Arduino / Motors, Mechanics, and Power / Re: Help with relay on: August 04, 2014, 03:34:31 am
But it says it's opto-isolated, and the LEDs in the isolators won't want that much current: they would surely be driveable by an i/o pin with a series resistor?

Could it be that the low side of  the relay, the 5V which is switched by the isolator, needs to provide that much current? I see there's a Vcc pin: maybe that's the one....

Do you have a link to a datasheet or schematic?
553  Using Arduino / Project Guidance / Re: SwitchCase (Question) on: August 04, 2014, 03:13:05 am
You'll need to give details of your hardware: a schematic will be good.... we don't know what you mean by "button", in the sense of not knowing how they're wired.

Do you have many buttons on one analog pin with a resistor ladder perhaps?- or is it a button on each of many digital pins.

Might actually be a case for "if".... "else if".... "else" rather.

Show us what you have...
554  Using Arduino / Project Guidance / Re: Clarification on power source(s)? on: August 04, 2014, 12:30:11 am
If you plug a 9V Wall-wart into the UNO external power barrel jack you can supply close to 1 A (800mA).
You can bus everything else to the UNO +5 V.

But, you should allow and Amp for a servo, so it really does need to be powered externally from the Arduino. Just make sure you hook all the grounds together.

Edit.... pic attached
555  Using Arduino / Programming Questions / Re: Limiting Decimal Places For LCD Print? on: August 03, 2014, 09:58:44 pm
Code:
Serial.println(myFloat,4)

That would give 4 decimals, but yep it should be 2 by default.

http://arduino.cc/en/Serial/Print
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