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1021  Using Arduino / Programming Questions / Re: Arduino Uno stops sending sensor information on: February 16, 2013, 06:40:01 am
Yes it works very well and is really easy to use. I use it on an AMS2302 (DHT22) sensor and compare temp results very favorably with a  Bosch BMP085 Baro/Temp sensor.

1022  Using Arduino / Programming Questions / Re: Adding prints appears to change reads on: February 16, 2013, 05:45:15 am
Or more specifically, What does the sensor do when you return it's output data as input data? confirm it?

1023  Using Arduino / General Electronics / Re: High Voltage Monitoring on: February 16, 2013, 03:22:07 am
22 M ohms x2 isn't hard to do with precision resistors. The last recommended 68K resistor should be a 100k pot for final calibration. Be EXTREMELY CAREFUL, WHAT YOU ARE WORKING WITH CAN KILL YOU QUICKLY
 It shouldn't be difficult to get an accurately calibrated voltage divider.

1024  Using Arduino / Displays / Re: SainSmart tft 3.2 lcd display not working. on: February 15, 2013, 06:42:57 pm
Short of trying to compile your code it looks all right. The lines uncommented are for the mega and the display id "UTFT myGLCD(ITDB32S,38,39,40,41); is the same I use with several of my own  3.2" displays which leaves the contrast pot. If you have a Mega for the Itead display there are 2 versions 1.2 and 2.0... The 1.2 version has a contrast pot that must be adjusted to be able to see the display properly.
It is a 10 turn pot so be careful because the leads to the pot are fragile and be patient... the adjustment is only 2 or 3 turns close to one end of it's rotation (Added).

1025  Using Arduino / Displays / Re: Connect LCD to Arduino UNO on: February 15, 2013, 06:30:28 pm
Either a link to, or an attached data sheet might bring more answers. I for one, am reluctant to go look up the data to answer your question.. It should be a part of the question as that is it's immediate relevancy.

1026  Using Arduino / Microcontrollers / Interesting. on: February 15, 2013, 05:03:54 pm
I found this in the new Elektor magazine advert:
"A 4004 microprocessor from 1971 consists of 2,000 transistors.
Current Itanium series processors contain more than 3,000,000,000.
Around 65 years since the transistor was patented (1947)...
I remember...

1027  Using Arduino / Microcontrollers / Re: More than 256K of memory? on: February 15, 2013, 04:31:36 pm
Unfortunately.. he didn't say much else.

1028  Using Arduino / General Electronics / Re: Current measurement on positive or negative side? on: February 15, 2013, 04:25:53 pm
It is still an inductive pickup, just different physics.

1029  Using Arduino / General Electronics / Re: Home automation on: February 15, 2013, 04:23:23 pm
Cat 5 will work just fine.

1030  Using Arduino / General Electronics / Re: Current measurement on positive or negative side? on: February 15, 2013, 04:06:31 pm
Recently I bought 15 LEM HAL 300 current transformers as surplus from Ebay (the price was Very Right) and one of these devices would be perfect for your application. The device has a 30? mm (approx) hole in it to pass through the main motor current carrying wire. Due to the inherent losses involved in getting the Allegro  device soldered in a suitable PCB (4 Oz Cu?) and connections to the controller and battery, a through hole or pass through device is really called for. The HAL 300's can be found for about $50.00... Mine for considerably less (New on Mfr's shipping material). But I see no easy way to get one to you.
The device can be placed anywhere in the motor power leads, hot or ground as it is totally isolated.The LEM device is spec'd from DC to 50 KHz and has an output similar to the Allegro device however it requires a +/- 12 - 15V split supply to bias the Hall effect circuitry. There are available 12 to 15 V isolated switchers that will supply those voltages. Or in short.. I personally don't think that the Allegro device is ideal for your application. My intent here is NOT to sell current transformers but to point out a more suitable device. I intend to make DC transformers by winding a multi-turn primary so I can use them for more reasonable currents... +/- 30 A = 10T primary. Unfortunately.. I had to buy 15 (at less than the single unit surplus price, much less). It just occurred to me that the motor current is likely going to be considerably less than 130 A since your load will be just the mower and batteries, I should think more like 10 - 20 A which is easier to deal with than the rated full load current and entirely do-able with FR4 PCB material (I would use double sided FR4 laminate and have it plated to 4oz/in with a lot of via's stitching the top and copper together).

1031  Using Arduino / General Electronics / Re: hacking into a spy camera on: February 15, 2013, 03:18:28 pm
Indeed, Dr Watson.
1032  Using Arduino / Programming Questions / Re: Writing Libraries on: February 15, 2013, 07:03:38 am
Thinking in C++ and Programming in C++, Nice, Free books.... Code too.
Not for beginners, though.

1033  Using Arduino / General Electronics / Re: bi-directional level shifter - analysis question on: February 14, 2013, 05:09:09 pm
Nice solutions for more than one or two lines, I wonder though if a quad package is less money than 4 BSS138  mosfets..? both are SMT and the IC is simpler to use... but I wouldn't consider it for breadboard use because it requires a BOB and the 2N7000's have wires, great for breadboarding. In my experience BOB's are nice for some types of development and better for finished projects but poor for breadboarding and unworkable for commercial enterprise for obvious reasons. For those reasons I rarely suggest  anything but breadboadable solutions except where considerations of safety or complexity dictate otherwise.

1034  Using Arduino / General Electronics / Re: Current measurement on positive or negative side? on: February 14, 2013, 03:11:12 pm
I realize it is counter intuitive But I'd place the sensor in the high side of the motor... because of the possibility of a failure in the power connections to the sensor or the sensor proper. If low side sensing fails then you  have full supply voltage on the ground leads.. If high side sensing fails you have no power to the motor, much easier to troubleshoot and much safer to work around. This is one of the reasons why switching grounds is not wise unless it is an absolute last resort -- do-able but inadvisable. Supplies may be switched but it is Always a last resort to switch or sense ground in any high voltage control circuit.
The Allegro ACS series current sensors have a 2KV isolation barrier between sense and sensed conductors so there should be no issues of that nature in using the sensor in the high side of the motor power circuit.

1035  Using Arduino / General Electronics / Re: bi-directional level shifter - analysis question on: February 14, 2013, 02:27:10 pm
Referring to the source of those illustrations, app note NXP AN10441.
My understanding of app note is this:
The gate is connected to the 3V3 source. When the drain  is high and the source connected to the 3V3 side  goes low the mosfet conducts and pulls the 5V side low. When the 5V side goes low it pulls the 3V3 side low through the Fet body diode.
The APP Note has a better explanation that I did here but I am essentially correct, I believe.
I have built several of these level shifters and found them to work perfectly both for single and dual direction bus's. This is applicable to any level translation, single or bi directional IIC, SPI or TTL level RS232. 2N7000 mosfets work well but the VGth is too low to work at any lower bus voltages. If your design requires lower bus voltages use the BSS138 mosfet. 
I attached the app note for reference.

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