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by techpaul
Thu Jun 12, 2014 11:39 am
Forum: Automation, sensing and robotics
Topic: Solar panel power output measurement with rpi
Replies: 19
Views: 4904

Re: Solar panel power output measurement with rpi

Update When putting external resistors on these inputs, you really need to follow creepage and clearance distances for 230VDC so you would need something like 10mm between each wire and each resistor.

To aoid any effects of higher voltages near each other and not near lower voltage areas
by techpaul
Thu Jun 12, 2014 11:35 am
Forum: Automation, sensing and robotics
Topic: Solar panel power output measurement with rpi
Replies: 19
Views: 4904

Re: Solar panel power output measurement with rpi

Thanks for the informative post. I'm thinking of getting a hall sensor for the current, that would be the safest. May well need an op-amp scaling stage, as a resitor divider or other resistive means will have problems with the existing onboard resistor dividers. For the voltage, wouldn't it suffice...
by techpaul
Wed Jun 11, 2014 9:49 pm
Forum: Automation, sensing and robotics
Topic: Solar panel power output measurement with rpi
Replies: 19
Views: 4904

Re: Solar panel power output measurement with rpi

Update rechecked the circuit of the ADC board you are thinking of using and it is a DIFFERENTIAL ADC wired up so the inputs are SINGLE ENDED. You WILL either need a hall effect sensor to measure current and porobably an op-amp stage to scale its output, or an external resistor and op-amp circuit to ...
by techpaul
Wed Jun 11, 2014 9:38 pm
Forum: Automation, sensing and robotics
Topic: hall effect sensor
Replies: 24
Views: 9958

Re: hall effect sensor

Do a search

Draw out what I have described

Look up switches as GPIO and explanations of resistors, what you are asking for is basically tell me all your electronics knowledge in a short reply, I have large books on the subject
by techpaul
Wed Jun 11, 2014 9:32 pm
Forum: Automation, sensing and robotics
Topic: hall effect sensor
Replies: 24
Views: 9958

Re: hall effect sensor

Pin 1 to 5V (as device needs min of 4V max of 30V for power)
Pin 2 to GND
Pin 3 to GPIO input of your choice

Either enable software pullup on GPIO input or put a pullup resistor about 1k will be fine between Pin 3 and 3V3

NOTE PULLUP RESISTOR TO 3V3

NOT 5V you will blow the pi
by techpaul
Wed Jun 11, 2014 9:24 pm
Forum: Automation, sensing and robotics
Topic: Solar panel power output measurement with rpi
Replies: 19
Views: 4904

Re: Solar panel power output measurement with rpi

DC voltage is 75 to 230V, DC current is max 5A. With two measurements taken (one voltage, before current, one current) you can work out power and many things. Easiest Voltage measurement is use 1% or better tolerance voltage divider so that at 250V it is still when divided down within ADC input ran...
by techpaul
Wed Jun 11, 2014 6:14 pm
Forum: Automation, sensing and robotics
Topic: Solar panel power output measurement with rpi
Replies: 19
Views: 4904

Re: Solar panel power output measurement with rpi

Really would help folks if you put up specs or links to the specs for parts of the system and how yours is configured. I have previously done a solar panel monitor addon for 20V DC max and 10A DC max Measuring the AC side is fraught with problems and it won't necessarily be 230V AC (RMS) it could we...
by techpaul
Fri Apr 18, 2014 1:44 pm
Forum: Python
Topic: I²C High Speed Datalogger for Acc- Sensor
Replies: 11
Views: 3664

Re: I²C High Speed Datalogger for Acc- Sensor

That's probably the best solution. It should be possible to send the data to the RaspPi over serial fast enough to keep up with the acquisition, although the protocol would need a bit of care in its design. So you could do continuous acquisition if you needed to. The Pi is fast enough to process th...
by techpaul
Wed Apr 16, 2014 11:32 pm
Forum: Automation, sensing and robotics
Topic: PCF8591 ADC too low sample rate
Replies: 3
Views: 1656

Re: PCF8591 ADC too low sample rate

Further note if you were to try the scheme of reading multiple bytes you can acheive more results by configuring as TWO differential analog inputs ensuring the inputs CH1 and CH3 are taken to same GND as your analog sensor/other circuit. Set for CH3 and auto increment will always get first reading t...
by techpaul
Wed Apr 16, 2014 11:21 pm
Forum: Automation, sensing and robotics
Topic: PCF8591 ADC too low sample rate
Replies: 3
Views: 1656

Re: PCF8591 ADC too low sample rate

Likewise not familiar with the quickwire and what your code is supposed to be doing For example why put in count += 1 which is not used elsewhere? However you would be better of sending command to start at CH 3 (when using 4 single ended inputs) of PCF8591 with auto-increment, then read THREE bytes ...
by techpaul
Wed Apr 09, 2014 11:13 am
Forum: Staffroom, classroom and projects
Topic: Redesigning the soldering iron!
Replies: 49
Views: 12686

Re: Redesigning the soldering iron!

I.... what would be more useful is for someone to come up with a device that can hold a pcb / strip board still to allow soldering but at the same time allow for the fact that components once soldered make the board less flat. maybe a anti static sponge, but as part of a unit, that can also hold so...
by techpaul
Mon Apr 07, 2014 2:41 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: wiringPiI2CReadReg16 - bug??
Replies: 10
Views: 1840

Re: wiringPiI2CReadReg16 - bug??

http://www.electrodragon.com/w/images/5/5f/RDA5807M_datasheet_v1.pdf - 2.5 Control interface Which says that the device is high byte then low byte in section 2.5 "For read transfer, after command byte from MCU, RDA5807M sends out register 0x0Ah high byte, then register 0x0Ah low byte,...." Similar ...
by techpaul
Mon Apr 07, 2014 2:14 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: wiringPiI2CReadReg16 - bug??
Replies: 10
Views: 1840

Re: wiringPiI2CReadReg16 - bug??

Post a link to the datasheet as it is rare byte order is not in there for 16 bit values.

You would have to take the function description and choice of extra function up with the author or make your own version.
by techpaul
Mon Apr 07, 2014 1:09 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: wiringPiI2CReadReg16 - bug??
Replies: 10
Views: 1840

Re: wiringPiI2CReadReg16 - bug??

redhawk wrote:If there's no standard for returning 16bit numbers wouldn't that make the wiringPiI2CReadReg16 function unreliable??
At most it should have a note about assumed byte order and consult datasheet on byte order of your device.
by techpaul
Mon Apr 07, 2014 12:44 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: wiringPiI2CReadReg16 - bug??
Replies: 10
Views: 1840

Re: wiringPiI2CReadReg16 - bug??

There is NO standard for byte order on I2C, SMBUS specifies low byte first but if your device does high byte first you will have to swap bytes.
by techpaul
Mon Apr 07, 2014 12:42 pm
Forum: Raspbian
Topic: How to check battery status?
Replies: 7
Views: 2401

Re: How to check battery status?

I have made addons for people in the past to do this on higher powered solar panel chargers you need external ADC and suitable circuit for the battery size (volts and max amps) of ALL the parts it will supply.
by techpaul
Mon Apr 07, 2014 12:35 pm
Forum: Troubleshooting
Topic: RPi does not boot, when GPIO is connected
Replies: 7
Views: 1957

Re: RPi does not boot, when GPIO is connected

Hello mahjongg, thanks for the response. I did not apply 5V to the PI gpio I rather used the 5V output of the GPIO. There is your problem, if you have connected ANYTHING like that linked diagram and applied 5V to the TSOP1738 then the output is being pulled up to 5V and 5V is being passed to the GP...
by techpaul
Sat Apr 05, 2014 9:11 pm
Forum: Python
Topic: I²C High Speed Datalogger for Acc- Sensor
Replies: 11
Views: 3664

Re: I²C High Speed Datalogger for Acc- Sensor

Hallo to all, thanks for the fast answers especially for the first post, now I know how to write more beautiful posts! I tried to find out what the maximum samplerate would be... Funktion ist easy: Init sensor --> wait for start --> read senor 5000 times an safe the data in a list get systime befor...
by techpaul
Sat Apr 05, 2014 9:10 pm
Forum: Python
Topic: I²C High Speed Datalogger for Acc- Sensor
Replies: 11
Views: 3664

Re: I²C High Speed Datalogger for Acc- Sensor

Hallo to all, thanks for the fast answers especially for the first post, now I know how to write more beautiful posts! I tried to find out what the maximum samplerate would be... Funktion ist easy: Init sensor --> wait for start --> read senor 5000 times an safe the data in a list get systime befor...
by techpaul
Sat Apr 05, 2014 8:27 am
Forum: Python
Topic: I²C High Speed Datalogger for Acc- Sensor
Replies: 11
Views: 3664

Re: I²C High Speed Datalogger for Acc- Sensor

sleep functions only give a minimum time from start of call, they do not guarantee timing for tjhings like sampling.

I would avoid print and file save while acquiring data samples to memory (an array/list)
by techpaul
Sat Apr 05, 2014 8:21 am
Forum: C/C++
Topic: SPI wiringPi issue
Replies: 5
Views: 3663

Re: SPI wiringPi issue

Hello (Im guessing Gordon will be straight on this but any one with info is welcome to comment) So I had a Pi connected via UART to a PIC the PIC was then connected via SPI to an ADC (MCP3301) and the ADC was connected to a variable resistance. And everything worked fine. Measure resistance and fee...
by techpaul
Sat Apr 05, 2014 8:03 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: 10 or 12 bit ADC chip I2C dip ?
Replies: 12
Views: 12139

Re: 10 or 12 bit ADC chip I2C dip ?

Just putting "i2c adc" into google came up with loads of selections with selling adverts for people like adafruit with 12bit and 16 bit I2C ADCs, even the datasheet link to a microchip 18bit I2C ADC. Sort out what resolution you actually need,, work out your max sampling rate you need and then find ...
by techpaul
Sat Apr 05, 2014 7:47 am
Forum: Python
Topic: Bit banging to read/write RDS info
Replies: 141
Views: 17263

Re: Bit banging to read/write RDS info

Because after the first read you have ENDED the I2C transaction with a stop condition. Also Joans comment on ACK/NACK are relevant. All I2C devices are then waiting for the next START condition followed by I2C address to know which device has to respond next. If you want three bytes from sequential ...
by techpaul
Thu Apr 03, 2014 8:05 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Reading analog and/or PWM signals
Replies: 10
Views: 2968

Re: Reading analog and/or PWM signals

The value read from the device (in this case, the measured current) is expressed by the ratio of "on" to "off" in a rectangular wave. Assume v is the value being measured, normalized to lie between 0.0 and 1.0. And a PWM frequency of 125Hz means it has an 8 millisecond period (1/125 Hz). At time t0...
by techpaul
Thu Apr 03, 2014 7:59 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Reading analog and/or PWM signals
Replies: 10
Views: 2968

Re: Reading analog and/or PWM signals

What sort of signal are you trying to read that you need 12 bits of resolution? The PCF8591 clock is tied to the I2C clock frequency. Run the I2c bus at 1 Mhz, and that is the sampling rate. You can but none of its analog path is guaranteed especially if you are auto muxing channels. You MAY get it...

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