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by mikronauts
Wed Jun 07, 2017 4:58 pm
Forum: Automation, sensing and robotics
Topic: Relays and failsafe
Replies: 27
Views: 3994

Re: Relays and failsafe

I was thinking about using a shift register or counter as follows: - 555 timer generates pulses for counter,Pi keeps clearing the counter, otherwise final count "disconnects" relay control from the Pi via logic. (active low logic from Pi, NOT overflow OR'd with Pi's output fed to relay, overflow als...
by mikronauts
Wed Jun 07, 2017 4:50 pm
Forum: Automation, sensing and robotics
Topic: analog input interfacing
Replies: 15
Views: 4142

Re: analog input interfacing

That is a nice looking hat. Their use of 150R resistors suggests they are running the ADC at 3v3, and common mode voltage differences are likely an issue. I agree, using three Pi's and three hats (if common mode issues are not an issue) would be a good solution. to the OP: Unless you can avoid diffe...
by mikronauts
Tue Jun 06, 2017 11:35 pm
Forum: Automation, sensing and robotics
Topic: analog input interfacing
Replies: 15
Views: 4142

Re: analog input interfacing

Depends of how the 4-20mA sensors are powered. Theoretically, you can just use a 250 ohm resistor, and measure the voltage drop across it, assuming no common mode voltage issues. The problem is that most power supplies these days do not use a transformer, and unless the power supplies to the sensors...
by mikronauts
Mon Jun 05, 2017 2:42 pm
Forum: Automation, sensing and robotics
Topic: analog input interfacing
Replies: 15
Views: 4142

Re: analog input interfacing

You may find my article helpful:

http://www.mikronauts.com/raspberry-pi/ ... and-howto/
binyameen panali wrote:i am new to raspberry pi. i have a requirement that need to connect 20 analog input to raspberry pi3. how can approach to it. sir please give me a solution
by mikronauts
Mon Jun 05, 2017 2:41 pm
Forum: Automation, sensing and robotics
Topic: CamJam Edukit #3 - What is best to power the Pi?
Replies: 10
Views: 1846

Re: CamJam Edukit #3 - What is best to power the Pi?

I recommend using USB power banks with a 2A+ output, and 5000mAh+ capacity, and a 4xAA (or larger) battery pack for the motors. Here are a couple of my bots using such power: http://www.mikronauts.com/robot-zoo/elf-2wd-pi-robot/ http://www.mikronauts.com/robot-zoo/hobbit/ Ok, this isn't really a nas...
by mikronauts
Thu Jun 01, 2017 3:24 pm
Forum: Automation, sensing and robotics
Topic: Datalogging Energy Meter via MODBUS
Replies: 3
Views: 2936

Re: Datalogging Energy Meter via MODBUS

I've done a lot of work interfacing Modbus (and other) devices to PC's running HMI & SCADA packages. For pure monitoring/logging it is fairly safe to write your own logging software, as long as you don't saturate your comm bus, especially for a non-critical home application. This assumes that your P...
by mikronauts
Thu Jun 01, 2017 3:17 pm
Forum: Automation, sensing and robotics
Topic: Relays and failsafe
Replies: 27
Views: 3994

Re: Relays and failsafe

What you are looking for is a watchdog dimer + safety circuit. One way of implementing such a circuit (as you are driving the relays high) would be to use a dual input AND gate to drive each relay. For each relay, one input to its AND gate would be the current Pi GPIO, the other the output from a wa...
by mikronauts
Wed May 31, 2017 5:34 pm
Forum: General programming discussion
Topic: SPI sends zero response. working with ADS868
Replies: 7
Views: 2268

Re: SPI sends zero response. working with ADS868

Each sample requires 32 SCLK based on the timing diagram you posted. I think there is a minimum of 8 SCLK periods between valid /CS, so minimum 40 SCLK periods per sample. To get 500ksps, you would need 20Mhz SPI clock, and be able to keep up with that data rate. Good luck. Hello, I am trying to com...
by mikronauts
Thu May 25, 2017 7:08 pm
Forum: General discussion
Topic: Servo Motor Jitter (?) when used with ultrasonic sensors
Replies: 4
Views: 1070

Re: Servo Motor Jitter (?) when used with ultrasonic sensors

1) Each distance reading can take up to (as I recall) 56ms

2) the detection beam width is ~20' so stepping by 1 degree is fairly useless
by mikronauts
Fri May 19, 2017 8:02 pm
Forum: Advanced users
Topic: Fast data writing to external SSD
Replies: 2
Views: 837

Re: Fast data writing to external SSD

Not possible on a Pi 3. You need an SBC with a separate gigabit NIC and at a minimum a working USB3 interface (some SBC's USB3 ports don't work well with drives), or better yet, a SATA interface. Sorry, you should have researched your I/O bandwidth needs for all your devices (camera, hd, nic) before...
by mikronauts
Fri May 19, 2017 4:06 pm
Forum: Beginners
Topic: 20+ 3.3V sources
Replies: 6
Views: 787

Re: 20+ 3.3V sources

There are up to 26 GPIO's available on the 40 pin header (not including the HAT i2c) - if you use the regular I2C, subtract two pins (you should do this) leaving 24 pins Notes: - SPI, if used, would subtract 4-5 pins - the serial port would subtract 2 pins Best option (unless you need to switch the ...
by mikronauts
Wed May 17, 2017 5:27 pm
Forum: Networking and servers
Topic: Project: Pi as audio jack NIC interface
Replies: 12
Views: 1671

Re: Project: Pi as audio jack NIC interface

You will also need a pink unicorn. Despite the funny above, I do not wish to be mean. Go read about how networks work. Pi's do not have mic inputs Even if they did, this would be ridiculously slow, after a horrendous amount of work. Here are some MUCH easier & faster methods: 1) A small Ethernet hub...
by mikronauts
Wed May 17, 2017 5:25 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: RS-232 RTS voltage levels?
Replies: 11
Views: 2542

Re: RS-232 RTS voltage levels?

Do yourself a favour, use a MAX3232 to translate the Pi's 3v3 signal levels to RS232 levels.
by mikronauts
Wed May 10, 2017 6:16 pm
Forum: Beginners
Topic: High Speed Function Polling for DAQ
Replies: 1
Views: 417

Re: High Speed Function Polling for DAQ

You are going about it backwards. First, you did not do your basic homework before choosing parts: 1) The LTC1864 has a maximum sampling rate of 250ksps, so 500ksps is simply impossible. 2) The Raspberry Pi SPI sport may have trouble doing 500ksps due to bit rate limitations, inter-transfer minimum ...
by mikronauts
Tue May 09, 2017 4:58 pm
Forum: Automation, sensing and robotics
Topic: PiZero to control 24VDC bi-directional motor
Replies: 20
Views: 2481

Re: PiZero to control 24VDC bi-directional motor

Sounds like you got two more bad ones. Try ordering the next one from someplace like adafruit, sparkfun, robotshop, pimoroni etc as they likely have good suppliers. FYI, I've used a lot L298N modules without issues, mind you I only order from 99%+ rated sellers. The one that lights the LED likely ha...
by mikronauts
Tue May 09, 2017 3:13 am
Forum: Beginners
Topic: Can I2C and GPIO Be Used On The Same Board?
Replies: 5
Views: 968

Re: Can I2C and GPIO Be Used On The Same Board?

Thank you - now I know I can count on more current!
mahjongg wrote:actually its more like 15mA per pin 50mA total for all GPIO's, but yes that won't drive relays directly, you need to use it to turn on a transistor, and don't forget the diode over the coil of the relay.
by mikronauts
Mon May 08, 2017 8:55 pm
Forum: Beginners
Topic: Can I2C and GPIO Be Used On The Same Board?
Replies: 5
Views: 968

Re: Can I2C and GPIO Be Used On The Same Board?

You will need to use a transistor or other driver as relays typically will not activate from the Pi's GPIO, which is typically only capable of 5mA per pin, 16mA total @ 3v3. Can GPIO And I2C be used on my PI3 I have the I2C in use right now and need to run a relay Thanks For Any Help :) Also if you ...
by mikronauts
Mon May 08, 2017 8:54 pm
Forum: Automation, sensing and robotics
Topic: Using 2 9V batteris as power supply
Replies: 3
Views: 730

Re: Using 2 9V batteris as power supply

9V batteries won't last very long, they usually only have about 200-250mAh capacity. Hi, I have a project where I have 2 9V batteries connected in serial as power source for 2 12V solenoids. I previously purchased the Battborg https://www.piborg.org/battborg but the battery pack with 8 AA batteries ...
by mikronauts
Mon May 08, 2017 8:48 pm
Forum: Automation, sensing and robotics
Topic: Interfacing ATmega 32 with RaspberryPi 3
Replies: 4
Views: 2585

Re: Interfacing ATmega 32 with RaspberryPi 3

I2C is the wrong choice for wiring between rooms. Google "RS485" for a good choice, and there are plenty of RS485 interface chips. Hello, I want to interface 4 ATmega 32 microcontrollers with RaspberryPi 3. These controllers will be placed in various rooms and monitoring various sensors. So I was pl...
by mikronauts
Wed May 03, 2017 7:10 pm
Forum: Automation, sensing and robotics
Topic: Tying HC-SR04 Sonar Sensors echo pin
Replies: 5
Views: 1144

Re: Tying HC-SR04 Sonar Sensors echo pin

http://abyz.co.uk/rpi/pigpio/python.html#set_mode after sending the trigger pulse, delay for a while, set to input, wait for signal A common trigger is a problem as the HC-SR04 modules will pick up each others signal. Better solution: use a combined trigger/echo pair for each sensor, and use a separ...
by mikronauts
Tue May 02, 2017 10:52 pm
Forum: Automation, sensing and robotics
Topic: Tying HC-SR04 Sonar Sensors echo pin
Replies: 5
Views: 1144

Re: Tying HC-SR04 Sonar Sensors echo pin

A common trigger is a problem as the HC-SR04 modules will pick up each others signal. Better solution: use a combined trigger/echo pair for each sensor, and use a separate GPIO per sensor. Then, trigger&read each sensor one after the other, you WILL have issues if you try to trigger them at once. Se...
by mikronauts
Sat Apr 29, 2017 6:25 pm
Forum: Automation, sensing and robotics
Topic: New to GPIO
Replies: 8
Views: 1532

Re: New to GPIO

You are welcome. If you have an oscilloscope, you can use that to measure the voltage from the pulses, however based on the description below (and assuming that the flow meter is powered from the 5V) you should be able to use a simple resistor based voltage divider. See http://www.mikronauts.com/ras...
by mikronauts
Tue Apr 25, 2017 4:46 pm
Forum: Off topic discussion
Topic: Congrats to Liz and Eben
Replies: 12
Views: 2097

Re: Congrats to Liz and Eben

Congratulations on a job well done! :)
by mikronauts
Fri Apr 21, 2017 4:31 pm
Forum: General discussion
Topic: Is it possible to upgrade RAM for the raspi?
Replies: 52
Views: 45464

Re: Is it possible to upgrade RAM for the raspi?

Does not everyone order huge Tesla coils, Van de Graaff generators, flux capacitors and naquedah??? It's just for upgrading my surface mount oven... (HEY! watch where you put that 15' ring!!!) Problem is, as far as I can tell, everytime somebody manages to build an inter-dimensional alternate time l...
by mikronauts
Thu Apr 20, 2017 5:10 pm
Forum: Beginners
Topic: Connecting multiple sensors to a PI3
Replies: 4
Views: 2065

Re: Connecting multiple sensors to a PI3

You may find my article helpful: http://www.mikronauts.com/raspberry-pi/gpio-experiments/raspberry-pi-and-hc-sr04-distance-sensor-interfacing-with-c-and-python/ Hello, i'm new to Raspberry PI and i just bought all my sensors that i want. HC-SR04: http://www.ebay.com/itm/262356608628?_trksid=p2057872...

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