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1  Using Arduino / General Electronics / Re: Jumper Wires M/M - maximum length on: Today at 06:27:44 am
2  Using Arduino / General Electronics / Re: Can't get ILI9325 panel to work, backlight only on: Today at 06:27:11 am
To answer my own question, for future reference and for anyone else dealing with this problem, i solved my problem. Apparently RX1 and TX0 on the Pro Mini boards are not D0 and D1 but D1 and D0 respectively. As soon as i switched those two cables my display started working.

Maybe the person who made your Pro Mini labelled them wrong. Those pins are a hard-wired function of the Mega328 chip.
3  Using Arduino / General Electronics / Re: cost effective capacitor for 3.3V regulator - what's used on the Pololu? on: Today at 06:24:13 am
Ceramics are usually the best type for this. If in doubt, use ceramic.

Second choice would be polyester.

Do NOT use electrolytic or tantalum.

Atmel wrote a paper on it, let's it is:

4  Using Arduino / General Electronics / Re: How can I add a wire grabber to my multimeter ? on: Today at 06:16:21 am
I use ordinary crocodile clips like these:

You can squish the metal tube (under the colored plastic) with pliers until they fit your probes snugly.

There's also special multimeter clips like these:  but they cost more.

5  Using Arduino / General Electronics / Re: Help selecting battery please? on: Today at 06:09:56 am
So what am I to do? Must I just make sure I never use the battery until it gets that flat?


At the very least you need to measure the battery voltage on the Arduino and go into a low-power mode when it reaches danger level (ie. shut down the laser, etc).

Even better is to power the entire system via a MOSFET and drive the MOSFET gate from a comparator so that the MOSFET shuts down when the comparator input reaches a certain voltage level.
6  Using Arduino / General Electronics / Re: Powering a 5v Arduino with 3.3v and using a resistor network for voltage droping on: Today at 04:41:29 am
Hello, I am powering an Arduino Pro Mini 5v with a Lipo battery which has a  maximum voltage of 4.2v and a minimum of 3.3v. I also need to power an NRF2401n+ with .9v - 3.6v but the voltage from a fully charged lipo is too high. I know I could lower the voltage with a diode, led or a resistor network but I was wondering which of these is most efficient?

Neither. Diodes and resistors don't work as power supplies when current draw is variable (eg. NRF2401n+).

Voltage drop across diodes is highly dependent on current. Resistors are just rubbish for power supplies.

A LM317 voltage regulator costs about 30 cents.

7  Using Arduino / General Electronics / Re: Two Arduinos with one USB 2 lead. on: Today at 03:59:46 am
No. You can't have two devices trying to drive a piece of wire simultaneously.
That's not quite what I meant. If I tell the IDE to upload to the Mega (in Boards), will it ignore the Uno and just upload to the Mega and vice versa? As I said, it seems unlikely. But I've put in a DPDT switch now and I'll test it tomorrow, after I've reassembled the box.

It might pop up some annoying dialogs about serial ports or something, I haven't tried it.

OTOH you could open two separate IDEs and switch between them when you throw your switch. That will probably work better.

This raises a question: Why do you need to use a single USB cable? Why not two?
8  Using Arduino / General Electronics / Re: Powering 45M of LED light strips safely on: Today at 03:51:17 am
so far no wires feel hot, the power supplies are running cool.

You need to grab a multimeter and measure the voltages at various points on the strips (start/end/etc).

Find out where the losses are, and how much.

9  Using Arduino / General Electronics / Re: Help selecting battery please? on: Today at 03:45:29 am
do you mean that if I use the battery till the voltage drops so low I am damaging the battery?

10  Using Arduino / General Electronics / Re: choosing a battery for Micro + accelerometer on: Today at 03:44:14 am
I have no idea. any suggestions on how to find out?

11  Using Arduino / Microcontrollers / Re: Bootloader question: Does it skip the first X bytes of the .HEX file? on: Today at 02:38:40 am
It all makes sense until I realized that the first 512 bytes of UNO or first 4KB of MEGA 2560 are for bootloaders.

No, the bootloader goes at the end of memory.

See Figure 26-2 in the datasheet
12  Using Arduino / Microcontrollers / Re: Alternative to 16U2 on: April 22, 2014, 01:22:07 pm
Well there are two different questions going on here. The OP stated he wanted to build his own arduino board and a second topic of quality/usefulness of inexpensive Asian nano/micro/uno boards.

If anybody wants to put an AVR chip in a breadboard and program it just to see how it's done then they probably should do it.

For building gadgets? The Pro Mini is unbeatable IMHO.

Unless you need USB connectivity, obviously ... or you can use a Tiny85 if it needs to be really tiny. Apart from that, they're unbeatable.

However that doesn't change my recommendation that a beginner should start off buying one 'real' arduino Uno board, just call it the 'entry cost' to our great community.  smiley-wink

13  Using Arduino / Microcontrollers / Re: Alternative to 16U2 on: April 22, 2014, 09:38:47 am
It's a good point but the sub-$3 range is for the China variety of the clone.  These clones often have varying pinouts, especially around the Vcc/Gnd area of the board.  So caution needs to be utilized and the realization that one board ordered today may differ from one board ordered two months ago.

Plus the FTDI connector is completely randomly oriented on them. You have to look where Vcc is every single time you connect one.

The other issue, which should be considered, is the need to have a soldering iron and decent skills in using said iron.  Even if you just need to solder the headers for breadboard use.  Soldering and unsoldering wires to the little boards will eventually cause copper foil lift at which time the board.

Yep. The first thing you need to do when you open one is get out the soldering iron. Not exactly beginner-friendly.

It is a cheap and viable solution, but not one that I would recommend for the "My First Arduino" award. 

Agree. Develop with the Uno, save the Pro Minis for building into the final gadgets.

My last shipment of 5 Pro Micros and 2 dead units... one was revived with reflashing the bootloader for the 32U4 but one is eternally dead.  The previous 10 Pro Micros were 100%.  2 duds out of 15 may be an unacceptable rate of failure and most newbies will be unable to flash the 32U4: something to think about.

I've gone through 30-40 of them and haven't had a problem yet (touch wood). Even so, I don't see that as a big deal. What's a few dead ones when they're $3 each with free shipping? Just make sure you always order plenty of spares so you're never in a hole waiting for slow shipments to arrive.

I usually buy the ones with ISP connector and flash them with optiboot as soon as I get them so the bootloader gets overwritten anyway.
14  Using Arduino / Microcontrollers / Re: Third PWM channel on ATTINY85 on: April 22, 2014, 03:28:38 am
Sounds like a problem with your Tiny85 core files or something like that.

Write a minimal program to just fade the blue pin, see if that works. If it doesn't, reinstall your Tiny85 files.

15  Using Arduino / General Electronics / Re: Where to find good single sided PCB on: April 22, 2014, 03:21:47 am
I've been using some Chinese copper clad circuit boards for a long while now, but now I need a board bigger then the 4"x6" boards I've used so far. 

I'm sure the Chinese can do big boards, too.
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