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by rgrbic
Wed Jun 25, 2014 7:59 am
Forum: Other projects
Topic: Fuel flow sensor and open collector signals
Replies: 70
Views: 9454

Re: Fuel flow sensor and open collector signals

At least he can try with different Vcc and pull-up resistor just to be sure. I suggest to record output to see what kind of signal we are dealing with.
You are right regarding Schmitt trigger, it is not crucial in testing phase.
by rgrbic
Tue Jun 24, 2014 2:38 pm
Forum: Python
Topic: linking python with mysql
Replies: 5
Views: 1824

Re: linking python with mysql

Don't forget to install python interface to mysql:

Code: Select all

sudo apt-get install python-mysqldb
by rgrbic
Tue Jun 24, 2014 10:47 am
Forum: Other projects
Topic: Fuel flow sensor and open collector signals
Replies: 70
Views: 9454

Re: Fuel flow sensor and open collector signals

The output stage of the sensor is probably not in saturation so you don't get the right voltage levels on gpio pin to recognize the pulses.
And when counting pulses I suggest to use Schmitt trigger to improve immunity to noise.
by rgrbic
Sun Jun 22, 2014 9:02 pm
Forum: Networking and servers
Topic: webserver DNS help
Replies: 7
Views: 2648

Re: webserver DNS help

And, in your router settings, forward port 80 to Pi local IP address.
by rgrbic
Sun Jun 22, 2014 8:01 pm
Forum: Networking and servers
Topic: webserver DNS help
Replies: 7
Views: 2648

Re: webserver DNS help

It is wrong IP address (it is local IP of your Pi). You have to point to your public IP which your ISP assigns to your router.
by rgrbic
Sun Jun 22, 2014 6:33 pm
Forum: Networking and servers
Topic: webserver DNS help
Replies: 7
Views: 2648

Re: webserver DNS help

Do you have static IP address?
by rgrbic
Sun Jun 22, 2014 5:55 pm
Forum: Beginners
Topic: Cool PV Inverter with Raspberry Pi + fan
Replies: 13
Views: 3153

Re: Cool PV Inverter with Raspberry Pi + fan

Very true, the fan is running at reduced speed so less airflow and you can't turn it off, but I could sleep with it 1m from my ear and as it's spinning well below it's rated speed it's life will be much longer than it's rated for - unless you're worried about saving every mAH of power you'd may as ...
by rgrbic
Sun Jun 22, 2014 4:07 pm
Forum: Beginners
Topic: Cool PV Inverter with Raspberry Pi + fan
Replies: 13
Views: 3153

Re: Cool PV Inverter with Raspberry Pi + fan

I'll try to explain several reasons why I suggested the scheme in my first post. You connected the fan between 5V and GND. Let's say that voltage regulator on RPi can provide 1A. RPi will draw something like 700 mA when working so around 300 mA is remaining to draw from 5V pin. I am not sure how muc...
by rgrbic
Sun Jun 22, 2014 12:17 pm
Forum: Beginners
Topic: Cool PV Inverter with Raspberry Pi + fan
Replies: 13
Views: 3153

Re: Cool PV Inverter with Raspberry Pi + fan

From your post I can't see how you connected the fan to RPi.
by rgrbic
Sun Jun 22, 2014 10:05 am
Forum: Beginners
Topic: Cool PV Inverter with Raspberry Pi + fan
Replies: 13
Views: 3153

Re: Cool PV Inverter with Raspberry Pi + fan

Do not drive fans directly from gpio pins. For example, use transistor and put some diode across fan for protection. Use optocoupler to isolate Pi from power part. Something like this (I sketch this in a few seconds maybe I missed something, resistor values depends on type of optocoupler and transis...
by rgrbic
Sun Jun 22, 2014 8:27 am
Forum: General discussion
Topic: Can't seem to assign IP address manually
Replies: 4
Views: 848

Re: Can't seem to assign IP address manually

The easiest way is to configure router to assign desired IP address to your specific MAC address. In my case works great, I just had to enter MAC address of Pi ethernet module in router static ip address configuration. In your case you have to enter MAC address of wlan adapter in router configuration.
by rgrbic
Sun Jun 22, 2014 8:13 am
Forum: Automation, sensing and robotics
Topic: Yet more DHT22 sensor code
Replies: 101
Views: 80950

Re: Yet more DHT22 sensor code

You should put pullup resistor in the case of 3.3V supply too.
by rgrbic
Sat Jun 21, 2014 11:57 am
Forum: Automation, sensing and robotics
Topic: bathroom ventilation with webinterface
Replies: 1
Views: 1898

Re: bathroom ventilation with webinterface

Look at websocket. It is bi-directional communication protocol. See this example . Hereby, I was reading ds18b20 temp sensor and the readings were sent to the web page every 2 seconds. Similarly, you can read your dht sensors and display information on your site. Easily you can add some buttons for ...
by rgrbic
Sat Jun 21, 2014 11:40 am
Forum: Troubleshooting
Topic: Start a Python Script from boot
Replies: 36
Views: 18561

Re: Start a Python Script from boot

You have to put path to your python script in rc.local file. Open the file with the following command:

Code: Select all

sudo nano /etc/rc.local
and before exit 0 write:

Code: Select all

python /home/pi/Desktop/program.py &
Make sure that your python script starts with the following line:

Code: Select all

#!/usr/bin/env python
by rgrbic
Fri Jun 20, 2014 10:16 am
Forum: Beginners
Topic: Temperature and CPU usage during the day
Replies: 7
Views: 3567

Re: Temperature and CPU usage during the day

Interesting numbers. But how did you get CPU usage over 100% ?
by rgrbic
Tue Jun 17, 2014 4:38 pm
Forum: Advanced users
Topic: Raspberry Pi webserver
Replies: 20
Views: 5820

Re: Raspberry Pi webserver

Try to reach your web page from machine on local network by typing Pi local IP address to browser address bar. If this works, try from outside by typing global IP adress. If you cant get the webpage then router settings are not correct.
by rgrbic
Tue Jun 17, 2014 11:18 am
Forum: Advanced users
Topic: Multiple Inputs (buttons)
Replies: 14
Views: 15090

Re: Multiple Inputs (buttons)

for sure i am missing something, but why not managing this with interrupts? they also have debouncing function embedded.. different callback function for different interrupt and you avoid even a "forever while".. I agree, but imho for beginner the best way is to start with loops and then move to in...
by rgrbic
Tue Jun 17, 2014 9:36 am
Forum: Automation, sensing and robotics
Topic: Wireless monitoring system using raspberry pi
Replies: 4
Views: 3582

Re: Wireless monitoring system using raspberry pi

My monitoring system consist of arduino nodes with sensors and NRF24L01 chips for wireless comunication with a main node. The main node collects the measurements from all wireless sensor nodes and send them over serial connection to the Raspberry Pi where measurements are stored into MySQL database...
by rgrbic
Tue Jun 17, 2014 9:27 am
Forum: Advanced users
Topic: Multiple Inputs (buttons)
Replies: 14
Views: 15090

Re: Multiple Inputs (buttons)

Dougie gave you one possible solution. However, keep in mind that mechanical buttons have a bounce effect. When you press the button, the input will bounce between high and low state for a few ms. Therefore, you will need to implement some kind of debouncing (software or hardware). Here you can find...
by rgrbic
Mon Jun 16, 2014 7:53 am
Forum: Automation, sensing and robotics
Topic: Motors
Replies: 15
Views: 4332

Re: Motors

Here are the images of the motor and magnetic sensor (magnetic contact switch)
by rgrbic
Sun Jun 15, 2014 8:58 am
Forum: Automation, sensing and robotics
Topic: Motors
Replies: 15
Views: 4332

Re: Motors

Few years ago I was partially involved in such project. I will post few images tomorrow.
by rgrbic
Sun Jun 15, 2014 8:53 am
Forum: Automation, sensing and robotics
Topic: controlling 230v from rPI - solution? pick holes at it!
Replies: 21
Views: 7359

Re: controlling 230v from rPI - solution? pick holes at it!

Between RPi and relays. The byvac board essentially has done this. The relays are controlled by its own micro controller. The pi sends the signal to the micro controller, the micro controller then switches the relay. There is no back emf from the relays to the pi. Then you don't need it (sorry, I d...
by rgrbic
Sat Jun 14, 2014 1:06 am
Forum: Automation, sensing and robotics
Topic: Wireless monitoring system using raspberry pi
Replies: 4
Views: 3582

Re: Wireless monitoring system using raspberry pi

My monitoring system consist of arduino nodes with sensors and NRF24L01 chips for wireless comunication with a main node. The main node collects the measurements from all wireless sensor nodes and send them over serial connection to the Raspberry Pi where measurements are stored into MySQL database....
by rgrbic
Fri Jun 13, 2014 11:13 pm
Forum: Automation, sensing and robotics
Topic: Motors
Replies: 15
Views: 4332

Re: Motors

DC motor can be used for this purpose. To drive the motor you need appropriate circuitry. If you want to have variable speed then something like L298N can do the task but you need to generate PWM signal. If you want to drive the motor with only one speed then simple switch like transistor can do the...

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