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1  Using Arduino / Project Guidance / Re: RC Switch 433MHz not receiving signals from flash trigger on: September 16, 2014, 07:13:30 am
From the description of the flash unit , its using FM, which means the receiver you have simply wont work, as its
an ASK (AM) receiver.
2  Using Arduino / General Electronics / Re: 0 Voltage from power supply when connected to peltier on: September 15, 2014, 06:13:40 pm
What is the specs of the peltier, ie power rating at what supply volts.
Laptop power supplies are protected from overcurrent and will shutdown if overloaded.
Most common peltiers run off 12V , so 19V is far too high.
3  Using Arduino / Project Guidance / Re: RF Receiver Range with Arduino on: September 13, 2014, 07:19:41 pm
Measure the voltage on the receiver board.
Needs to be very close to 5V .
If the voltage is low , (less than 4.9 V) the receiver will appear to be deaf.
4  Using Arduino / Project Guidance / Re: Working with RF Module on: September 13, 2014, 07:06:40 pm
Those modules are based on the SC2262 / SC2272 encoder decoder chips and are used for simply sending a 4 bit nibble
from transmitter to receiver.
They use the same protocol as the RC switch library, as they are often used for remote control power points.
You cant send hi speed data though, as the decoder chip takes about a second to decode a valid frame.
5  Using Arduino / General Electronics / Re: Can I drive an N-MOSFET with an NPN-Transistor? on: September 07, 2014, 06:34:04 pm
Those are inverting drivers.
They will work , but will reverse the PWM output state  of your Arduino so that PWM = 0 will be full on.
Try and find a non inverting driver.
6  Using Arduino / General Electronics / Re: Can I drive an N-MOSFET with an NPN-Transistor? on: September 06, 2014, 06:57:00 pm
Ideally, the best way to drive hi power fets is with a dedicated FET driver, like one of these.
http://www.futureelectronics.com/en/technologies/semiconductors/analog/drivers/mosfet-igbt-drivers/Pages/2809358-MIC4422YN.aspx?IM=0

They are pretty cheap, usually around $1 or less, have sufficient current capacity (9 amps for this one)  to turn a FET hard on and off in under 10 ns and can be driven by either a CMOS or TTL input , so you can drive them straight from an Arduino output pin.
Fet drivers are pretty common ICs , so lots of manufacturers make them.
7  Using Arduino / Project Guidance / Re: Getting data from 10 Arduinos wirelessly on: September 06, 2014, 04:44:11 am
How often will the wireless transmitters be transmitting?
This type of problem depends entirley on how reliable you want the project to be.
Can you afford to lose data?
A Master Slave arrangement is the best option , but does require bi directional transmission.
8  Using Arduino / General Electronics / Re: Can I drive an N-MOSFET with an NPN-Transistor? on: September 02, 2014, 06:29:51 pm
The IRFZ44 has an input capacitance which ranges from 1500 to 2300 pf, which is not unusual for hi power fets.
If you want to PWM the fet, its important that whatever is driving the gate can provide enough current to charge
the gate capacitance in a much shorter time than the pwm rate, otherwise the fet wont ever actually turn on hard
and will get hot.
9  Using Arduino / General Electronics / Re: 315Mhz transmitter, push button version on: September 02, 2014, 04:56:00 am
The cheap 433.92 Mhz ASK radios do not transmit the state of the data pin.
They only transmit changes in state on the data pin , but the data must be continually changing.
You must have either a Micro controller or a data encoder like an SC2262  to make them work.
10  Using Arduino / Sensors / Re: Multiple DHT22 on same pin? on: August 30, 2014, 04:43:15 am
No.
The DHT22 is not addressable, so if you have more than one on the same wire, they will both try and send their data at the same time, which will give garbage.

11  Using Arduino / General Electronics / Re: using a buck converter as constant current source on: August 27, 2014, 08:14:09 pm
Theres very little differance in design between a normal buck converter which provides a constant voltage
and one which provides a constant current.
All you need to do is add 2 extra components to make a constant current source.
One is a low value sense resistor which goes in series with the leds , and the other is an op amp
to amplify the voltage across the current sense resistor, which is then fed back into the switcher chips
voltage ref input.
If you use a chip like a ua78s40 which is very similar to a MC34063, but includes a catch diode and a spare op amp
you dont need any extra components.
12  Using Arduino / Project Guidance / Re: Solar powered Arduino on: August 27, 2014, 07:56:28 pm
Powering devices from Solar is quite an exercise, in so far as determining the power budget and the Solar Panel size and
battery capacity.
There are many factors to consider, but if you need the device to be reliable, ie not stop working then you need to look at the worst case scenerio for the Solar generation, which is usually maximum sun hours in the middle of winter, plus an allowance for
1 to 2 weeks of consistantly cloudy weather.
http://pveducation.org/pvcdrom/properties-of-sunlight/calculation-of-solar-insolation

You then also need to accurately determine the devices power consumption,over at least a day, if its variable.
Its a fun thing to do though, especially when you eventually get it right.


13  Topics / Home Automation and Networked Objects / Re: about RF Switch 433 Mhz on: August 26, 2014, 05:15:35 pm
You can improve the odds of the remote switch being in the correct state by periodically retransmitting
the command code to the switch, eg transmit the on / off code every 5 minutes.
Still not 100% reliable though.
14  Using Arduino / General Electronics / Re: MC34063 Boost w/ external NPN not starting up on: August 25, 2014, 06:00:25 pm
Thanks Crossroads, there had to be a way.
To install the files in Ltspice, copy the mc34063.lib file to the lib directory.
Copy the mc34063.asy file to the sym directory, which is in the lib directory.
The mc34063_buck.asc is a good example which can be played with.
Just mod the circuit to suit your boost circuit.

15  Using Arduino / General Electronics / Re: MC34063 Boost w/ external NPN not starting up on: August 25, 2014, 12:52:30 am
I cant figure out how to upload files on this forum.
If you can send me your email address, Ill send you the LTspice model for the MC34063.
My email address is mauried@tpg.com.au
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