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1  Topics / Home Automation and Networked Objects / Re: Best cheap and simple 433MHz modules with good range on: August 17, 2014, 12:45:36 pm
It is homemade.

I use the following sensors:
Wind direction & Speed:   Sparkfuns Weather Meters
Rain:   Sparkfuns Weather Meters
Pressure sensor:   BMP085
Humidity & Temperature:   DHT22

Arduino MCU:Atmega1284 with RTC & LCD.
The RF-modules are the cheap ones from ebay.

Database/Web server run on a Cubieboard.


2  Topics / Home Automation and Networked Objects / Re: Best cheap and simple 433MHz modules with good range on: August 17, 2014, 09:05:09 am
I use virtual wire.

My weather station (50m away from my house) sends real time and historical data to my indoor modules.
First I tried to power my indoor Arduino (8Mhz) with 3.3V and lost a lot of transmissions. Then I tried to power it from a 5V USB/Serial adapter and it worked a lot better.
I also added the capacitors to get a more stable voltage (big cap) and to filter out interferences (small cap).

One Arduino recives weater data and stores it in a database (serial -> python -> database).
I have also a second Arduino which display the real time data on a LCD.  First I powered it with 3.3V because the LCD was a 3.3V model, missed a lot of transmissions. Changed to 5V and it worked much better.

I also have more transmitters, two (weather station, homemade energy meter) use 12V and three use 5V (sensors). 12V is better but 5V works good to.
Try 5V first, if you miss a lot of transmissions try a higher voltage on the transmitter.

3  Topics / Home Automation and Networked Objects / Re: Best cheap and simple 433MHz modules with good range on: August 17, 2014, 05:58:15 am
Hi!

I use a lot of cheap 433Mhz modules with 17cm wire antenna.
No problem to send 50m and through a wall.

I have noticed that they do not work well when powered from low voltage (3,3V). The high voltage (up to 12V) the better on the transmitter.
Also the reciver works best with 5V.

I have tested a lot to increase the range and noticed that if I put capacitors on VCC and GND I get a bit better stability.
One big bulk capacitor and a small 0.1uF.
The capacitors are optional and you will get a good result without them.
4  Using Arduino / General Electronics / Re: Ampere meter with internal shunt resistor safe for 30A? on: August 14, 2014, 03:24:15 am
I am quite sure that the extra text came after I contacted the seller smiley
Yesterday I copied and pasted the "Package Content" text and send to the seller, no "(internally installed) " anywhere.

But it is good that the seller corrected the description.

5  Using Arduino / General Electronics / Re: Ampere meter with internal shunt resistor safe for 30A? on: August 14, 2014, 12:14:41 am
Thanks, for your input.

I was just abit unsure to put 30A through the meter, the terminals are not that big.
Also sent a message to the seller of the meter and he replied that there should be no problem to use it with 30A.
6  Using Arduino / General Electronics / Ampere meter with internal shunt resistor safe for 30A? on: August 13, 2014, 11:46:09 am
Hi!

I bought the following ampere meter http://www.ebay.com/itm/151314913968?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649.

I thought I would get a meter and a external shunt resistor but I only got the meter.
So I think it has a  internal shunt resistor (I have seen that meters with external shunt often have a "resistor symbol" and a mV rating).

Is it common to have a internal shunt resistor for a 30A meter? I don't want it to burn up or something smiley

 
7  Using Arduino / General Electronics / Re: Huge voltage drop from H-bridge (4*N-channel Mosfets) on: July 06, 2014, 02:17:14 pm
Guess I should have done my homework before I started to solder my own H-bridge.

I have ordered some P-channel mosfets now. The FET driver ICs seems really good but they are quite expensive.
While I am waiting for delivery I will use relays.

The bridge is for a solar tracker I have made. A Attiny85 wake up from sleep every 5 minute and read two LDRs, adjust (if needed) a linear actuator for 1 second before it goes to sleep again.
The Attiny85 & LDR part work very well but I need a motor driver.

Relays work but for how long? 12 times every hour * 8760 hours (one year) equals 105120 switches!

 

8  Using Arduino / General Electronics / Re: Huge voltage drop from H-bridge (4*N-channel Mosfets) on: July 06, 2014, 12:54:44 pm
Thanks all!

Now I have some options to think about.

1. Buy P-channel mosfets and rebuild the H-bridge.

2. Use a higher voltage power-supply and step down the voltage to the motors (motor only used 0,4A when I measured).

3. Use 12V and step up the voltage to the gates.

4. Buy a driver IC
9  Using Arduino / General Electronics / Re: Huge voltage drop from H-bridge (4*N-channel Mosfets) on: July 06, 2014, 10:22:28 am
Thanks, for the reply.
I do not have any P-channel mosfets. I will order some from ebay.
Any recommendations? FQP27P06 and irf9530 are cheap.

Is it possible to get my current N-channel H-bridge to work without a driver chip? (Just wondering)
10  Using Arduino / General Electronics / Re: Huge voltage drop from H-bridge (4*N-channel Mosfets) on: July 06, 2014, 10:11:16 am
Hi!

I attach a new schematic. Realy need a better program than mspaint for drawing schematics smiley

I get 7,6V when measuring over the motor.
Q1, Q2, Q3 and Q4 are irf520.

No MCU is connected when testing. I just manually apply a voltage at R1 or R2.
11  Using Arduino / General Electronics / Huge voltage drop from H-bridge (4*N-channel Mosfets) on: July 06, 2014, 08:33:57 am
Hi!

I have made a simple H-bridge with four IRF540. (see attached picture, the symbols are NPN-transistors instead of N-channel mosfets but else everything is the same)

I drive the gates with 12V. Everything works, I can change direction but the voltage to the motor is only ~7V instead of 12V when I measure.

I don't use PWM, only need to swith the motor on/off one second every 5 minute.

Is something wrong with the use of four IRF540 instead of two p-channel mosfets and two n-channel mosfets?
I would like to know if it should work before I continuing to look for bad wiring.
12  Community / Exhibition / Gallery / Re: Water level alarm that uses a pressure sensor, sends SMS on: June 17, 2014, 02:08:43 pm
Hi Bengpaul!

I'm sorry but I have given away the "alarm", it is installed 300km from my home so I can't give you any more details except the code.

/Olof
13  Using Arduino / General Electronics / Re: Measuring AC frequency (48-58V), will this work? on: June 11, 2014, 12:28:22 pm
I already have good code to count frequency. I made the code for my function generator.
Basically I use interrupts and timer1 to count the time between pulses.

If the frequency exceeds 800Hz I change method to "pulses over time" because it works better for higher frequencies.

Back to the topic. Diode + 4N35  or H11AA1. It doesn't  matter both work but the diode + 4N35 generate fewer interrupts.
14  Using Arduino / General Electronics / Re: Measuring AC frequency (48-58V), will this work? on: June 11, 2014, 10:56:22 am
As soon as I get some time off I will test the circuit.
I think I will add a Atmega8, MAX7219 and a 7-seg display to build a very cheap frequency  counter.

I think the frequency should be the same as the wind turbine rpm.  Guess I should not assume things like that when I have no training in electronics smiley

15  Using Arduino / General Electronics / Re: Measuring AC frequency (48-58V), will this work? on: June 11, 2014, 01:21:45 am
So if I wan't to measure the frequency of a variable voltage between 10-58V then I need a 4K resistor.

58V  / 4 = 14,5mA (0.841W) * 0,2 = 2,9mA
10V / 4 = 2,5mA * 0,2 = 0,5mA

Or use less current when measuring. Maybe a 20K resistor will work fine without getting interferences.

I really appreciate the help, thanks.
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