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991  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).

992  Using Arduino / General Electronics / Re: hacking into a spy camera on: February 15, 2013, 03:18:28 pm
Indeed, Dr Watson.
993  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.

994  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.

995  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.

996  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.

997  Using Arduino / Programming Questions / Re: Issue with GPS Ublox GY-GPS6MU1 on: February 14, 2013, 05:12:25 am
[EDIT]... Why are you using SoftwareSerial at all, There are 3 HW serial ports Serial1, Serial2 and Serial3 remove the software serial stuff and where the software serial object is replace it with  Serial1,2 or 3.
The Ublox 6 is the one I'm familiar with and that green light is the "Fix" indicator, If it isn't blinking the device has yet to update it's ephemeris and will produce little useful nav or time data without that fix.
There are commandss that can be sent to the GPS receiver for reducing power and keeping the ephemeris current as well and it comes with some instructions as well.
Perhaps you might try the Adafruit GPS or the Mikal Hart TinyGPS libraries and their examples.
You would also do well to read the various wiki articles about GPS as well as the header files for the suggested libraries for any other useful information.
There is a utility for configuring the U-Blox GPS receivers u-centerSetup- that I found on
Electrodragons wiki page (I bought one form them) that is used for configuring that device, I think as well as determining sats that the receiver can seen and how well, Really interesting BUT:
Apart from the above the software if it works with your U-Blox device  and it DOES need a specific FTDI driver as I remember it was a CP2102 although I had no issues with 4 F/F jumpers and an FTDI converter and I think it was a CP2102 but I don't remember for sure or if a PL29XX.. was used I do remember it being quite interesting.
It was an interesting look into GPS as a whole.

998  Using Arduino / General Electronics / Re: Power Supplies on: February 14, 2013, 02:11:09 am
A Manifesto? or a historical document?, The collected gossip or How to pick a bad power supply...
Either answer fits... Unfortunately... Along with lefty I have never found that to be the case.
Sure old transformer devices have  those issues... but why would anyone with any sense use one when there are Good Switchers.. and even lLinear Regulator modules to provide Accurate power?
The point is that ALL of us at one time or another have committed that error... Once, from your "Manifesto" it sounds like you had a bad run of luck or you didn't learn the first time.

999  Using Arduino / Programming Questions / Re: Using other IDEs to develop on: February 13, 2013, 05:01:53 pm
Notepad++ is a Gnu project and as such essentially free except for the usual and I would love it if it could be integrated too, I have several multi-file sketches and cut and paste gets . Difficult at times. I tried it and I had to give it up. It was more trouble than it was worth.

1000  Using Arduino / Programming Questions / Re: NRF24L01+ Getting Started Sketch Timing Problem on: February 13, 2013, 04:53:57 pm
Several people have reported issues with the nRF24XX and Mega 2560's it seem that there isn't enough bypassing on the 3V3 rail. A 22 uF electrolytic and a .1uF ceramic capacitor should fix the issue or that was what was reported. It seems that the Mega hasn't enough bypassing because in every case the Uno worked with the RF24LXX module. It was substitution of a 3V3 source from an Uno that located the Mega 3V3 source fault.


1001  Using Arduino / General Electronics / Re: Mosfet -pmw to gate resistor on: February 13, 2013, 04:04:54 pm
And that's the truth...

1002  Using Arduino / LEDs and Multiplexing / Re: Need Help 4-bit Binary Counter With Parallel Load on: February 12, 2013, 09:46:22 am
@pwillard.. You got a new crystal ball?
1003  Using Arduino / Networking, Protocols, and Devices / Re: Honeywell barometric pressure sensor (I2C): diagnostic condition??? on: February 12, 2013, 09:25:39 am
The first link doesn't return me a valid data sheet... So any real advice is there... The device is a 3V3 bus Do you have a level shifter installed between the Arduino and the sensor. It won't work without the translation from 3V3 to 5V. There are many solutions for this issue. NXP (Phillips) has an app note that deals with this subject. I've attached it for your reading. Adafruit has a solution as well as Sparkfun.. But they are about $3.00 - 6.00 Ea this one cost me $.50 to implement (2 2N7000 Mosfets).

1004  Using Arduino / Sensors / Re: Mini Aref on: February 12, 2013, 09:09:04 am
One of the best descriptions I've heard yet and I think better because English isn't your first language.

1005  Using Arduino / Sensors / Re: Density sensor of solids on: February 12, 2013, 09:05:40 am
Destructive testing of a sample might return the information you want...

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