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511  Using Arduino / Programming Questions / Re: arm control on: August 05, 2014, 05:41:59 am
I haven't had a proper look yet, but all of the "if" lines like this one with the =:

if (rightButPress = HIGH)

.... need to use the == and look like this:

if (rightButPress == HIGH)

Edit: see the warning on this page
512  Using Arduino / Motors, Mechanics, and Power / Re: Solenoids on: August 05, 2014, 05:38:26 am
You def need external power and transistors (or solid state relays: something which can switch the high current) and also the so-called flyback diode, backwards across the solenoid.

This tutorial should get you started.
513  Using Arduino / General Electronics / Re: Multiple I2C devices on: August 05, 2014, 04:34:30 am
My take, and the way I have a DS1307, 2x EEPROMs and an adafruit OLED screen connected even as we speak, is that the SDA and SCL are buses so you connect everything in parallel.

edit... in fact, thinking about it, I might re-wire my breadboard and use on set of +- power rails as SDA / SCL buses which will make it easier to add and remove devices in future.
514  Using Arduino / Programming Questions / Re: Permanent Saving to EEPROM on: August 05, 2014, 03:39:34 am
Good and acceptable solution option.
(How do I reward good answer in this form?)

Glad to help.

There's a + Karma button....
515  Using Arduino / Programming Questions / Re: Permanent Saving to EEPROM on: August 05, 2014, 03:27:58 am
Read it back.... if it's now different, write new values, otherwise don't.
516  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.
517  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.....
518  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.
519  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.
520  Using Arduino / Project Guidance / Re: read pot help wanted on: August 04, 2014, 09:50:26 am
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.
521  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.....
522  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.
523  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
524  Using Arduino / Motors, Mechanics, and Power / Re: Help with relay on: August 04, 2014, 03:51:22 am
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....
525  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?
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