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1  Using Arduino / Networking, Protocols, and Devices / Re: Sparkfun OBD-UART -Arduino MEGA power problem on: January 26, 2014, 07:16:38 pm
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I am using a SparkfunOBD-UART board to connect to a Mega.
A link would be good.

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My software sketch
Sharing it would be good.

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but only if I power the Sparkfun board by a toggle, off then on
I haven't a clue how a "toggle, off then on" can provide power. An explanation would be good.



The CAN UART board made by Sparkfun when using it with a CAN hi/Lo input via the DB-9 connector needs 12 volts to run. ( This is often from the car's 12 volt battery ) This 12 volts is what I toggle . If it is ON I switch off the 12 volts and then back on again. If OFF alrerady and i switch it on the sketch ruins fine and gets the CAN data. I have checked other sketches and it is not a function of the sketch just something to do with using the ARduino and the Sparkfun board. Unlike most hardware that runs with an Arduino the Sparkfun board does not get any power from the Arduino just needs the 12 volts. Possible it could have just been connected to the +5 on the Arduino but Sparkfun did not plan it that way.
The fact that the same problem occurs with different sketches eliminates the Arduino but the post was put here as some of the Arduino uses might have also used a Sparkfun UART-OBD11 board.
I hope this explains the situation better.
2  Using Arduino / Networking, Protocols, and Devices / Sparkfun OBD-UART -Arduino MEGA power problem on: January 25, 2014, 05:02:58 pm
I am using a SparkfunOBD-UART board to connect to a Mega. My software sketch runs fine getting data via CAN-BUS but only if I power the Sparkfun board by a toggle, off then on  If I don't do this the Sparkfun cannot seem to connect to the CAN and no data is RXd.
This is repeatable and seems independent of the ARduino so it is probably something in the protocol of the Sparkfun .. Any ideas as although I could make the power up sequence be such that it all work this happens.s it seems a poor engineering solution as I don't know why this happens.
3  Community / Gigs and Collaborations / code help on: February 06, 2013, 12:09:40 am
I am looking for someone to provide the code to read using an I2C serial from a MAX11068 chip to an Arduino Mega. The 11068 data is available by googling Max11068.pdf. I will pay for this .
4  Using Arduino / LEDs and Multiplexing / Re: 112 switches need reading on: November 19, 2012, 03:21:29 pm
Yes,  I am stupid today!! Adding the diodes is easy .
In case you wondered what this is all about.. here's the quick view.. I have 112 cells in a nom. 400 volt battery pack for my electric car that I am building. Need to know as a minimum if the pack is discharging  as when being driven if any cells are lower than the low limit . Also when charging except that I just have shunting across any cell that has reached full charge allowing the rest to get fully charged too. This is called a BMS, battery management system, and is the biggest PITN . There are chips that are meant to do this but the ones from MAXIM have shown a failure mode that makes their use questionable, ( EMAIL ME DIRECTLY IF INTERESTED IN THIS )  so I am designing a simple system with relays for isolation. Each cell will have it's own relay and the contacts are what is forming the 7 x 16 array. I can have number of these open or closed depending on the individual cell condition. so diodes it is.
5  Using Arduino / LEDs and Multiplexing / Re: 112 switches need reading on: November 19, 2012, 01:37:21 pm
Thanks for the demultiplexer idea, Not sure that you need the diodes , my thoughts run like this:  assume it is a 7 x 16 crosspoint array and they are A thru G for the the 7 lines and 1 thru 16 for the 16 lines. If A is connected to 1 and A is also connected to 2. Then if you put a hi on the pinin that is A and read out the 1 thru 16 lines then you would get a Hi on pinin 1 and also pinin 2 , this then says that both A1 and A2 are closed. What am I missing when you say I need diodes?
6  Using Arduino / Motors, Mechanics, and Power / Re: my first big project - BMS - is it possible? on: November 18, 2012, 01:23:37 pm
I have set up 112 cewlls using the Max11068 eval boards. Not cheap since each board for 24 cells costs $100, but it can do everything you want including having an I2C out that can connect and be read in an Arduino. I did start this in testing and found that one of the boards ( I have 5 total ) failed and Maxim are working on the problem, it might be a real problem with the chip isolation design... don't know yet but will post when I do. In the meantime I am going with a simple system using a shunt IC for balancing during charging and a low voltage monitor chip when discharging and a relay for isolation. Only problem is relay power comes from the batteries so not good if the batteries are left off charge for any length of time. To get over this requires a latching system and with 112 cells it adds up quickly to more $$$.
7  Using Arduino / LEDs and Multiplexing / Re: 112 switches need reading on: November 18, 2012, 11:41:05 am
THanks , the switches are just SPDT, not connected to anything yet,  so I can do whatever I like. Looks like the array is simpler than using shift registers with PISO system. I have to do a PCB to mount all the switches which are the other half of the switches on 112 relays.
Even using another Mega is less than doing a board with the CMOS logic as it already has the serial built in.
8  Using Arduino / LEDs and Multiplexing / Re: 112 switches need reading on: November 18, 2012, 01:57:12 am
thanks for the advice. I suddenly realized that I can arrange the 112 as a 7 x16 array , read it with an Arduino and send the data to the main Mega... I am sure that the code to read an array is in a library... anyone know where I could look for this? The switches are all fully floating so making them as an array is simple.
thanks
9  Using Arduino / LEDs and Multiplexing / Re: 112 switches need reading on: November 17, 2012, 09:27:11 pm
THey are as you described external and I don't have any way to connect to the Arduino except as a serial line. I am hoping someone will have some idea of what CMOS logic chips might do the job. I realize that this is not a simple problem but I am willing to build the PCB to put the chips on it. Just haven't worked with CMOS for some time and need some help with the CMOS family, decoders, etc... also need to take the logic output and have a way to read the data. I did think that a way would be to use 2 MEGAs, since that would give me enough inpins and then send the data from these to the remote ARduino via the serial line. Although not cheap it it seems that it might be the simplest... Opins?
10  Using Arduino / LEDs and Multiplexing / Re: Single transistor constant current power led driver. on: November 17, 2012, 08:56:54 pm
There are chips that are constant current drive for LEDS, usually for long strings of LEDS or those running on a 12 volt supply, usually they are switching types and so more efficient. Look up LED drivers.
Using a transistor as a constant current device works well if the voltage is high enough compared to the load. Also the higher gain device the better. BTW You could use the Arduino to provide a constant current by including it in the control loop. This would allow you to try different currents without rewiring. It will be a PWM output with a analog input from a resistor in series with the LED (S). You will need to put a filter ( resistor /cap ) at the analog input.
11  Using Arduino / LEDs and Multiplexing / 112 switches need reading on: November 17, 2012, 08:48:04 pm
I have 112 switches that output a 0 or 5 volts. I need a way to send this to an Arduino, MEGA2560  , by the serial port, using some CMOS logic or? so that I can tell which switches have changed state. Normal condition is that all 112 are HI=5 volts. Ideas please. The Arduino and the switches are about 5 feet apart but in a noisy environment.
thanks
12  Using Arduino / Motors, Mechanics, and Power / Re: Using a transistor to control a motor? on: July 06, 2012, 03:47:18 pm
You can use a transistor to control a motor but I suggest that you check out the chips that are designed to handle the PWM aspects. Do a search for motor control chips. It is very, very important that you use a chip that has pulse by pulse current control. This is because without it the current, when the motor is not yet turning, will be very high and then when the pulses turn it off the voltage produced will blow your transistor. If you just want to turn it on or off without any speed control then a MOSFET will do the job but it needs protection from the high voltage on turn off and the inrush current when turned on.
Easier and best to use a dedicated chip and use the Arduino to send a control signal to the chip.
13  Using Arduino / Motors, Mechanics, and Power / Re: my first big project - BMS - is it possible? on: July 06, 2012, 03:41:29 pm
Yes!! it is possible to use the Max11068 connected to an Arduino to read any number of cells ( upto 120 ).
There is no problem except that the most negative part of the battery pack is connected to the maxim gnd. All the rest are floating and the 11068 mux handles this perfectly. I have a system for an ecar that uses this chip and uses 112 cells. Nearly 400 volts!!
No need for relays. The documentation for the 11068 and the eval board 11068eval kit explain most of what you need to do. How you connect to the Arduino via the SDA and SCL outputs on the lowest max11068 using Ic2 or SMB depends on how you want to handle the data stream and where you are displaying the data. . I will publish code when I have it thoroughly tested. If anyone in this forum has done this please let me know and we can compare notes.
14  Using Arduino / Programming Questions / Re: how to handle multiple switches on: March 06, 2012, 11:42:08 pm
THanks for heads up on debouncing. I think I understand that part. The part I am missing is how to have complete prgm that goes through all the states and then keeps looping. I think that I need the prgming format info but not sure as I don't know what to ask for? If a pushbutton is pressed momentarilly and there is a long prgm how can I be sure that the status of the button was noticed since the port is not constantly monitored, and Arduino might be looking elsewhere at that critical time.
I could do the debouncing and latching externally, with discrete logic chips, to the Arduino but I am trying to avoid all that complications. More ideas and help please
15  Using Arduino / Programming Questions / how to handle multiple switches on: March 06, 2012, 08:51:45 pm
I have 4 pushbutton momentary switches that put out either a 5 volt or a 0 depending if I want any of the four lamps to flash or not. This is to be controlled by a MEGA. The flashing rate is to determined in the prgm. If a button is pressed then the corresponding lamp should flash. It should stay flashing until the button is pressed again. I am new to prgming C++ but have some experience in Basic. Can any one give me some idea of the code, or tell me where to look, for this. Thank you.
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