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1021  Using Arduino / General Electronics / Re: How do I control/replace this rotary switch with an Uno? on: January 15, 2013, 10:41:00 pm
Might need 2 relays... If that switch has an off position too.. One for On1 and one for On2... it does appear to be a 2 circuit or SPDT with an off position and possibly a both position.

Bob
1022  Using Arduino / General Electronics / Re: Sensing without a microcontroller on: January 15, 2013, 10:37:54 pm
I wasn't talking about the Led sensing anything, I was talking about sensing the Led.. Your original question I believe..

Bob
1023  Using Arduino / Displays / Re: Arduino Mega LCD Shield - How to use free pins? on: January 15, 2013, 10:33:55 pm
I use an 20 cm 40 pin cable I bought on the internet... Not Ebay. It's female to female and on one end I use a male to male gender bender. I took the Elecfreaks shield and removed the pins that I could and replaced them with the stackable headers... It works well But better I think when my shield from Crossroads arrives.

Bob
1024  Using Arduino / Displays / Re: SOLVED - unable to make it work 1.8 SPI TFT 128x160 on: January 15, 2013, 10:24:23 pm
Isn't the SD card 3V3? that will require an interface to work properly. There are great tutorials and sample sketches from Adafruit, I bought mine there but I can't remember about the SD card.

Bob
1025  Using Arduino / Networking, Protocols, and Devices / Re: Testing UP501 GPS on: January 15, 2013, 10:16:03 pm
There are 2 baud rates one for the serial monitor and one for the GPS device, when you see the Adafrui...  message the serial monitor baud rate is correct... what of the other.?

Bob
1026  Using Arduino / Networking, Protocols, and Devices / Re: UART to RS485 half duplex on: January 15, 2013, 10:09:34 pm
My understanding is that the RS-485 bus is to be centered about 2.5 V because the signalling is differential and it was for longer wires that the terminator is required to damp the ringing so the data transitions don't over run each other and they are really a necessity at higher baud rates.

Bob
1027  Using Arduino / General Electronics / Re: A few simple questions about inductors.. on: January 15, 2013, 09:46:17 pm
Two Quick things:
1. The R in the circuit represents the circuit resistance or the curve would look as you describe.
and
2. Use a large capacitor... > 5000 uF  and if the wire run was long I'd use a great deal more... 10X more.
Or more. The point is that the capacitor is invisible until the load hits and then it's invaluable.

Bob
1028  Using Arduino / General Electronics / Re: My hacked ATX PSU on: January 15, 2013, 07:15:34 pm
Well Yeah the power supply IS very Nice... If I had the money for both the supply and the shipping..
But a re purposed Motherboard for the connector and the power supply from the case that the Mo-board came out of can usually be had for free.. So about $10.00 and a few hours time would get a good fixed but multiple output voltage supply  which was the thread's original subject..For that matter a 0 to 2 A,  .9 to 20 V Switcher type circuit assy can be had for about $12.00 from China... with built in CC/CV controls (10T pots PCB Mtg) and either switch selectable current  or voltage monitoring. Not 5A... Well Not $105.00 either, even with the modifications required to make it look professional in appearance and plug into the mains wiring Too (It takes a discarded Laptop PSU  and about $25.00 in parts, 2 pots and the switches, etc)... Also to be found @ any Radio Shack.
Seriously that looks perfect for a 3V3, 5 and 12 V PSU with great current capacity and a better price AND using ALL NEW Parts can done very nicely for about $60 - $70.00... On the cheap... FREE. there are also many variant's on the idea of free.

Bob
{Edit Added link to part source}
You can get the part here among several..
http://www.ebay.com/itm/170929163665?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649
And free shipping Too, mine took 9 day's to arrive
1029  Using Arduino / LEDs and Multiplexing / Re: RGB SMT LED Cube, resistors, drivers, and shift registers. on: January 15, 2013, 02:02:38 pm
If you want really straight wires try heating the wire to a low red heat while applying tension to the wire. Allow the wire to cool naturally and you will have annealed the wire.. No more bends or gentle curves in the wire. This also is useful to relieve work hardening of copper and alumininum as well.

Bob
1030  Using Arduino / Microcontrollers / Re: analogReference Attiny85 on batteries on: January 15, 2013, 01:44:45 pm
Since the 'normal' ADC measurements are ratio-metric with the Vcc as the Analog Vref it would make more sense to use Vcc and not the internal 1.1 V vref because then Vref will be changing as the batteries do and this will preserve the ratio and not the absolute difference which is what you need.

Bob
1031  Using Arduino / Microcontrollers / Re: amazon nano clone (china) fails on: January 14, 2013, 10:41:45 pm
Return it to Amazon.. If you have powered it properly and used it properly then it is defective, Have you had it for more than 30 days?.
If not Amazon is Always good about returns... I have purchased local stock from SainSmart, sold by Amazon that failed. 3.2" 320 X 240 displays.
I bought one that was bad out of the box, I emailed them and got a RMA that day and shipped back the part.. Free too.

Bob
1032  Using Arduino / General Electronics / Re: Sensing without a microcontroller on: January 14, 2013, 10:30:11 pm
No, the LED's aren't really conducting much and there is always the issue of different types of LED's used in different cubes... And the typically low current used for testing.. Not too promising..   IMO

Bob
1033  Using Arduino / General Electronics / Re: Frequency Counter Kit from sparkfun on: January 14, 2013, 10:23:56 pm
If it doesn't light up.. you made a mistake in assembly. I've taken the liberty of attaching the schematic and aside from the connectors and socket there are only 12 parts besides the controller.. As Always re-check your soldering, inspecting for bad solder (Bridges) or no solder.. skipping a pin is a common error.. After 50 years I still do that occasionally.
There is no power switch so I dearly hope you didn't connect it to Anything But 5 V DC as it would damage both the display and the processor.
There isn't a lot more that bypassing and the crystal and load cap's.. A TTL 74S90 would extend the frequency range by a factor of 10 as 'selected' 74S90's can go to 100 MHz, divide by 2 and then 5 for a total of a factor of 10 division of the input signal. But that's for later... need to get it working first.

Bob
1034  Using Arduino / General Electronics / Re: MOSFET as switch and power monitor on: January 14, 2013, 01:05:41 pm
My previous post was somewhat confusing.. So
OTOH there are 2 common kinds of drivers both open collector. An NPN transistor is used to bias a P ch Mosfet on and a PNP transistor is used to bias an N ch Mosfet. Or both or either as required.
There are also hybrid IC's that are used to drive mosfets where there are no sources of voltages greater than 5 to 10 volts as some high power Mosfets require.
The 'common drivers' are trivial to implement and the 'Driver' IC's do require some special handling and this was the reason for my comment on redundancy.

Bob
1035  Using Arduino / General Electronics / Re: MOSFET as switch and power monitor on: January 14, 2013, 12:51:08 pm
2 quick things. 1 copper wire has a positive temperature co-efficient that is when it gets hot it's resistance increases which means that while it "Looks" like the current is going up it is actually going down because of the increase in resistance of the copper. It's all right to use copper for connecting things as the rules that that into consideration but not to measure current with because of it's 3300 PPM positive temp co..
And 2. There are many "Logic Level" mosfets available, using a driver and a higher voltage Vgs mosfet is kind of redundant.

Bob
{Edit RKJ}
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