Show Posts
Pages: [1] 2 3 ... 34
1  Using Arduino / General Electronics / Re: 315Mhz transmitter, push button version on: Today at 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.
2  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.

3  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.
4  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.


5  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.
6  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.

7  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
8  Using Arduino / General Electronics / Re: MC34063 Boost w/ external NPN not starting up on: August 24, 2014, 06:26:06 pm
Boost converters draw more current when they start, than when they are running, as when the converter starts
its looking into charging the output capacitor which looks like a short circuit initially.
If you dont get anywhere, I suggest you download LTspice4 , http://www.linear.com/designtools/software/?gclid=CJOJ2aaFrcACFcQHvAodG1oA_Q#LTspice

and simulate your circuit.
You can them measure the peak inductor current at start time and run time .
9  Using Arduino / General Electronics / Re: MC34063 Boost w/ external NPN not starting up on: August 24, 2014, 03:53:46 am
I use this design tool to calculate the optimum values for MC34063 switcher circuits.
http://www.nomad.ee/micros/mc34063a/

It gives you the optimum values, for any config , Buck,boost or inverting.
The important value is the Inductor peak current , as it determines what the inductor size
needs to be to avoid saturating.

10  Using Arduino / General Electronics / Re: MC34063 Boost w/ external NPN not starting up on: August 23, 2014, 08:17:36 pm
Ok, all I can suggest is you try another switcher chip.
Normally if the triangle wave generator is running, but no switching is happening
then either Q1 or Q2 in the switcher chip is fried.
Its usually Q1 that goes.
Id try just using another MC34063 just by itself without an external pass transistor
and Id also suggest you increase the Inductor value to at least 150 uH with the same saturation
current as the existing inductor.
33 uH is very marginal at startup.
11  Using Arduino / General Electronics / Re: MC34063 Boost w/ external NPN not starting up on: August 23, 2014, 06:09:17 pm
See if you can measure the resistance between pin 1 and pin 2 of the MC34063.
You will have to disconnect one of the pins from the rest of the circuit to do this.
This is to determine whether the switcher transistor , Q1 in the chip is fried.
You should get very high resistance.
12  Using Arduino / General Electronics / Re: MC34063 Boost w/ external NPN not starting up on: August 23, 2014, 05:09:03 am
Whats the maximum and minimum  load current?
13  Using Arduino / General Electronics / Re: MC34063 Boost w/ external NPN not starting up on: August 22, 2014, 11:58:54 pm
Sounds like a stuffed transistor, but the issue will be what broke it.
No switching sounds like the main switching transistor Q1 in the MC34063 is also stuffed.
Whats the saturation current of the series inductor?

14  Using Arduino / Project Guidance / Re: RF Link Kit problem / Virtual Wire on: August 22, 2014, 01:22:26 am
You have bought the wrong RF link kit.
That kit has a encoder and a decoder on the board with the transmitter and receiver.
Its most likley based on the SC 2262 / SC 2272 4 bit data encoders, which can send a 4 bit value from one to the other.
You dont need Virtual Wire.
To send an 8 bit value , you will have to break it into 2 , 4 bit values , and then send the 4 bit values one after the other.
15  Using Arduino / Motors, Mechanics, and Power / Re: Arduino Mega hanging on Solar Power on: August 21, 2014, 05:57:49 pm
What do you mean by this
"switch over from solar PV module to Battery"
With any Solar Powered system, the battery should provide the power all the time.
All the Solar Panel should do is charge the battery.
There should never be any switchover from the battery to the Solar panel.
A circuit diagram would help.
Pages: [1] 2 3 ... 34