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by rgrbic
Mon Jul 28, 2014 9:47 am
Forum: Automation, sensing and robotics
Topic: Stepper motors with external Power Supply?
Replies: 14
Views: 5321

Re: Stepper motors with external Power Supply?

keep in mind that one motor will draw about 100 - 150 mA. So if you are attaching other stuff to your RPi (like usb devices) the whole setup maybe will not work. The better approach is to use separate power supply. To lower the current you can put resistors. See here for the example how to connect u...
by rgrbic
Fri Jul 25, 2014 6:45 pm
Forum: Automation, sensing and robotics
Topic: L293 dc motor - quick switch from forward to reverse problem
Replies: 6
Views: 2164

Re: L293 dc motor - quick switch from forward to reverse pro

Trying to reverse it by reversing power supply connection will require additional energy which will be drawn from power supply. Did you consider motor braking by putting the resistor across it which will dissipate the mechanical energy?
by rgrbic
Tue Jul 22, 2014 9:16 pm
Forum: Advanced users
Topic: High Power Stepper Motor
Replies: 15
Views: 5224

Re: High Power Stepper Motor

+1 The stepper motor performance can be improved by adding serial resistor to each coil. Basically, the motor coil can be modelled as serial RL circuit where R is resistance and L is coil inductance (lets forget the emf). When the DC voltage is applied to such circuit, the current gradually increase...
by rgrbic
Tue Jul 22, 2014 8:57 am
Forum: Networking and servers
Topic: Raspberry Pi system monitor
Replies: 2
Views: 1446

Re: Raspberry Pi system monitor

It is still in development phase, I will provide it when it will be finished. But you can see the web page here.
by rgrbic
Tue Jul 22, 2014 8:42 am
Forum: Networking and servers
Topic: Raspberry Pi system monitor
Replies: 2
Views: 1446

Raspberry Pi system monitor

We made a Web page for our Raspberry Pi system monitoring. The page refreshes every second. The screenshot is below, any comments/suggestions are welcome.
by rgrbic
Mon Jul 21, 2014 11:26 am
Forum: General discussion
Topic: 5V relay connection problem
Replies: 16
Views: 2493

Re: 5V relay connection problem

Maybe simple RC network between gpio and transistor base can filter this toggling.
by rgrbic
Sat Jul 19, 2014 1:47 pm
Forum: General discussion
Topic: 5V relay connection problem
Replies: 16
Views: 2493

Re: 5V relay connection problem

At what rate are relays clicking?
by rgrbic
Fri Jul 18, 2014 10:21 am
Forum: Advanced users
Topic: High Power Stepper Motor
Replies: 15
Views: 5224

Re: High Power Stepper Motor

The cheapest solution is to use L297 + L298N. With such configuration you can control the current through windings to match the required torque (to pull the window and hold it in desired position). And in the same time to prevent heating of the motor. You can buy such drivers or you can do it yourse...
by rgrbic
Thu Jul 17, 2014 9:25 am
Forum: Advanced users
Topic: High Power Stepper Motor
Replies: 15
Views: 5224

Re: High Power Stepper Motor

The serial resistor can be added to motor winding (choose appropriate wattage!). Better solution is to control current.
by rgrbic
Thu Jul 17, 2014 12:32 am
Forum: Advanced users
Topic: High Power Stepper Motor
Replies: 15
Views: 5224

Re: High Power Stepper Motor

These drivers cant handle such current. L298N can be used in parallel mode - google it
by rgrbic
Wed Jul 16, 2014 12:25 pm
Forum: General discussion
Topic: 5V relay connection problem
Replies: 16
Views: 2493

Re: 5V relay connection problem

Use pull down resistor.
by rgrbic
Wed Jul 16, 2014 12:15 pm
Forum: Beginners
Topic: How to creat Database?
Replies: 5
Views: 1170

Re: How to creat Database?

here you can find information how to read temperature sensors and store readings to mysql
by rgrbic
Sun Jul 13, 2014 5:31 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Turning 12v IR light on and off
Replies: 4
Views: 1162

Re: Turning 12v IR light on and off

Check this site, part "Using an NPN transistor".
by rgrbic
Sun Jul 13, 2014 4:20 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Turning 12v IR light on and off
Replies: 4
Views: 1162

Re: Turning 12v IR light on and off

Use transistor as a switch. I believe you have standard IR light for cameras which is usually powered with dc 12V, 500 mA. So choose appropriate transistor which can handle that current.
by rgrbic
Sat Jul 12, 2014 6:39 am
Forum: Automation, sensing and robotics
Topic: Plant watering installation
Replies: 5
Views: 3561

Re: Plant watering installation

Everything you said is ok and it would be interesting to expand the project. But if the whole setup have to be powered from the battery pack then microcontroller should be used.
by rgrbic
Fri Jul 11, 2014 4:32 pm
Forum: Automation, sensing and robotics
Topic: DHT22 remote sensor with batteries
Replies: 28
Views: 9165

Re: DHT22 remote sensor with batteries

I suggest you to make your own board with microcontroller that has SPI interface (it is needed for communication with nrf module). The communication with sensor and nrf module can work on MCU internal oscillator. All can be powered from 3.3V.
by rgrbic
Fri Jul 11, 2014 9:07 am
Forum: Automation, sensing and robotics
Topic: DHT22 remote sensor with batteries
Replies: 28
Views: 9165

Re: DHT22 remote sensor with batteries

You can achieve very low power consumption with atmega. Google it, something like "atmega power save". Nrf24l01 can be turned off or disabled when not transmitting the data so it will draw very little current.
by rgrbic
Fri Jul 11, 2014 8:54 am
Forum: Automation, sensing and robotics
Topic: DHT22 remote sensor with batteries
Replies: 28
Views: 9165

Re: DHT22 remote sensor with batteries

Gigabyte2 wrote:Ok, can I make a standalone transmitter with DHT and NRF24 (without using Arduino)?
No. You need microcontroller.
by rgrbic
Fri Jul 11, 2014 8:45 am
Forum: Automation, sensing and robotics
Topic: DHT22 remote sensor with batteries
Replies: 28
Views: 9165

Re: DHT22 remote sensor with batteries

I have seen that it works @ 2.4Ghz like the WiFi adapters..there are some problems for that? Can I power Arduino with NRF24L01 and DHT22 with 6 AA batteries for a long time? There is a tutorial for communication between Raspberry and Arduino with NRF24L01? There a couple of nrf24 libraries for ardu...
by rgrbic
Fri Jul 11, 2014 7:45 am
Forum: Automation, sensing and robotics
Topic: DHT22 remote sensor with batteries
Replies: 28
Views: 9165

Re: DHT22 remote sensor with batteries

Gigabyte2 wrote:How nrf24l01 works? It's stable?
Yes, I didn't have problems with these modules. However, there are two types. In my experience, cheaper ones (with pcb antenna) are working on 10-20 meters distance. The ones with amplifier and sma antenna are working up to 100 - 150 meters.
by rgrbic
Thu Jul 10, 2014 3:42 pm
Forum: Automation, sensing and robotics
Topic: Plant watering installation
Replies: 5
Views: 3561

Re: Plant watering installation

RPi is quite overpowered for such task. If I understood correctly, you want to periodically read some sensor (let say twice a day) and if necessary activate pump for a few seconds. I suggest some microcontroller which has much smaller energy consumption.
by rgrbic
Thu Jul 10, 2014 2:56 pm
Forum: Automation, sensing and robotics
Topic: DHT22 remote sensor with batteries
Replies: 28
Views: 9165

Re: DHT22 remote sensor with batteries

Gigabyte2 wrote:Can I make it easely with Xbee?
Yes. I used nrf24l01 transceivers because they are cheap.
by rgrbic
Thu Jul 10, 2014 2:23 pm
Forum: Automation, sensing and robotics
Topic: DHT22 remote sensor with batteries
Replies: 28
Views: 9165

Re: DHT22 remote sensor with batteries

I have done similar project. Check this page. There is one central node which collects measurement from wireless sensor nodes and send readings to RPi.
by rgrbic
Wed Jul 09, 2014 6:28 pm
Forum: Beginners
Topic: Raspberry PI connected with Attiny
Replies: 6
Views: 1911

Re: Raspberry PI connected with Attiny

puchacz wrote:So when I power up Attiny by 3.3v from RPI, my logic 1 will be phisically 3.3V and I will be possible to connect it directly?
Yes. But be careful what you are hooking up to the 3.3V, I am not sure how much current it can provide.

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