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61  Using Arduino / General Electronics / Re: How can I find out why a small DC motor won't work? on: April 06, 2014, 06:04:26 pm
Could be worn out brushes in the motor, especially if its fairly old.
Usually you can pull small DC brush type motors apart and that will allow access to the brush assembly.
If the commutator is open circuit then its unreparable.
62  Using Arduino / Motors, Mechanics, and Power / Re: Motors used in car thermatic fans. on: April 01, 2014, 08:23:26 pm
Thanks, most of the current fans for cars so far that Ive seen in car shops  are the 2 wire models, so brush type motors still.
Seems that they arnt designed to be repairable if the brushes wear out,as they sure dont come apart easily.
63  Using Arduino / Motors, Mechanics, and Power / Re: Motors used in car thermatic fans. on: April 01, 2014, 04:09:45 pm
Thanks for the pictures.
I guessed brush type motors also, but fan motors because they have to run for long periods of time usually dont have brushes
as the brush life would be pretty bad.
Maybe brush life has been improved .
64  Using Arduino / Motors, Mechanics, and Power / Motors used in car thermatic fans. on: March 31, 2014, 05:43:01 pm
Anyone know what type of technology these motors use, ie are they conventional brush motors or some kind of brushless motor.
They are usually rated at 12V DC and draw anywhere upwards of 6A .
Most fan motors are usually induction types, but obviously thats not possible in  a car.
What Im trying to figure out is what the life of such a motor is , if it has to run continuouslly.
Very little info on the Net about these technology wise.
65  Using Arduino / General Electronics / Re: Measuring crystal frequency - HELP! on: March 31, 2014, 06:50:49 am
The parallel resistor is in the AVR, you cant switch it out.
You dont need an external parallel resistor.
66  Using Arduino / General Electronics / Re: Help with building simple RF module. Please help on: March 30, 2014, 05:08:52 pm
The reason you wont find any tutorials on how to build simple data transmitters and receivers is simply because you cant.
Data receivers that will do what you want are not simple.
You need a full super heterodyne receiver which requires RF stage , Mixer , IF amplifier , Detector ,Data slicer , AGC control, Crystal  Synthesised local oscillator and antenna .
You also need specialised test gear including a signal generator and a frequency counter or spectrum analyser.
Unless you have a very strong background in Radio Comm design then forget building the radio part of your project and buy
readily available radios.

67  Using Arduino / General Electronics / Re: Measuring crystal frequency - HELP! on: March 30, 2014, 04:56:07 pm
The parallel resistor is normally in the PIC or AVR.
Without it , the oscillator wont run at all.
68  Using Arduino / General Electronics / Re: Help with building simple RF module. Please help on: March 30, 2014, 12:41:18 am
The difficulty is building a simple receiver that will work for receiving data.
Low power FM transmitters generally assume you already have some kind of FM receiver, as building an FM receiver is anything but trivial.
As you can buy already built 433 Mhz Transmitters and receivers for less than $4 each , its silly to even consider building your own.
69  Using Arduino / General Electronics / Re: Measuring crystal frequency - HELP! on: March 29, 2014, 04:47:14 am
Crystal oscillators in PICs and AVRs are supply voltage dependant for a given crystal frequency , and also very dependant of the value of the capacitors from either side of the crystal to ground.
The crystal itself is also important, as it needs to be a parallel mode crystal.
Usually, the datasheet for the Pic or AVr will tell you what the optimum capacitor values should be .
You can measure the frequency with a X10 Cro  probe connected to the output pin of the oscillator, but the best most reliable way
is to use the CLKOUT option which most PICs and AVRs have and simply measure the freqency on the CLKOUT pin.
70  Using Arduino / General Electronics / Re: Measuring el. consumption non-contact? on: March 28, 2014, 01:23:04 am
Whats the nature of the load that is being supplied and how accurate do you want the result to be.
Current clamp type measurements generally arnt all that accurate , and they assume constant voltage and unity power factor.
71  Using Arduino / Project Guidance / Re: Lowest power method for 2 digit LCD on: March 27, 2014, 06:03:00 pm
Have a look at one of these.
http://ww1.microchip.com/downloads/en/DeviceDoc/41250F.pdf
Inbuilt LCD driver which runs even when the Micro is in sleep mode..
72  Using Arduino / General Electronics / Re: Serial communication question on: March 25, 2014, 07:56:00 pm
Try sending the data slower, lower baud rate , or leave a pause between the characters being sent.
Software Serial doesnt have a receive buffer, so data can get corrupted if data is coming in , but the CPU is doing something else
like writing to a display.
73  Using Arduino / General Electronics / Re: Wireless sound from one arduino to another on: March 24, 2014, 01:41:58 am
This is by no means a trivial project.
You will need some kind of audio amplifer which also provides a Dc offset so that the microphone output
falls within the range of the Arduinos A/D converter.
You will also need some kind of simple audio codec to convert the sampled audio into a digital bit stream to feed to the radio.
At the receiving end you will have to do the reverse, and then somehow recover the audio and feed it to an audio amplifier and then a speaker.
Hope you are an experianced Arduino programmer.

74  Topics / Device Hacking / Re: car fm radio antenna hack on: March 21, 2014, 12:36:03 am
AM means Amplitude Modulation.
FM means Frequency Modulation.
In either case, you need some hardware that can function as a modulator.
The Arduino cant, as theres nothing in it that can perform this function.

75  Using Arduino / General Electronics / Re: AC Freq Measurement on: March 18, 2014, 07:00:08 pm
How accurately do you want to measure the frequency?
Thats what determines the complexity needed.
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