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1306  Using Arduino / Programming Questions / Re: How to create a 38 Khz pulse with arduino using timer or PWM? on: April 24, 2012, 10:42:10 pm
Hi,
   If all you are trying to do is generate a 38khz carrier, switched at 1khz, why not do it in hardware with a single 556 Timer, that what this does -

http://rcarduino.blogspot.com/2012/03/punk-consoles-and-ir-transmitters-555.html

It costs about 2 dollars to build.

Duane B

rcarduino.blogspot.com
1307  Using Arduino / Project Guidance / Re: Tach and speed attachinterrupt on: April 24, 2012, 10:35:04 pm
Hi,
   I can't comment on your choice of sensors, but what your are trying to do in principle is well within the capabilities of an UNO. If you wanted more interrupts to monitor all four wheels, you could use the pcintchange library -

http://rcarduino.blogspot.com/2012/03/need-more-interrupts-to-read-more.html

Duane B

rcarduino.blogspot.com
1308  Using Arduino / Programming Questions / Re: Book on: April 24, 2012, 10:08:33 am
Hi,
   Thats true, but its still interesting to look at the assembler, I assumed that some functions would be inlined but they are not, its also interesting to see how many cycles anything involving a volatile long takes - read four bytes from memory to register, do something to four bytes, write four bytes back to memory.

  I am interested because the RC Channel signals I am dealing with are 500us from neutral to full throttle, I will often have a situation with several pending interrupts, the lowest priority interrupt can be forced to wait 8us or more which shows up as a 2% error in the desired output signal.

I have half a dozen strategies to reduce this and will be working on them over the coming few days.

Duane B

rcarduino.blogspot.com

1309  Using Arduino / Programming Questions / Re: WinAVR, AVRStudio or AVR-GCC on: April 24, 2012, 08:57:05 am
Hi,
   Thanks, I have just been looking at AVR Studio 5.1 and notice that it says 'no longer need to download a separate tool chain'. I am downloading it now to have a look.

Duane B

rcarduino.blogspot.com
1310  Using Arduino / General Electronics / Re: op amp audio amplifier circuit help/suggestion on: April 24, 2012, 07:34:12 am
Hi,

I want to extend my vu meter to be frequency based, I was thinking of having three or four bands with each band having it's own vu meter based on the resistor ladder/comparator circuit.

I am not sure whether I should take the signal through three opams with unity gain which will feed three copies of the input signal to three separate filters or whether I can skip this buffer stage and go straight into a branch to three filters without the opamps splitting out/bufferong three copies of the signal first to three separate filters.

I have added an additional line out from my Audino synth so either way I can figure out what works using the Audino as a frequency generator.

If anyone has some previous experience, please share otherwise I will get back withnhow I get on in a few days time.

Duane

1311  Using Arduino / Motors, Mechanics, and Power / Re: servo Clock on: April 24, 2012, 07:23:24 am
Hi,
If you are referring to my post I am concerned that you read some part of it as recommending 18volts into a servo. Please don't do this, it's three times more voltage than you should be applying, can you also point me to the part of my post that lead you to this thought, I will change it so that others do not read it the same way in future.

Thanks

Duane B

rcarduino.blogspot.com
1312  Using Arduino / Programming Questions / WinAVR, AVRStudio or AVR-GCC on: April 24, 2012, 06:32:46 am
Hi,
   From this thread it looks as if AVRStudio is the current environment for ATMega development, is this correct or is there an alternative I should look at ?

Thanks

Duane B

rcarduino.blogspot.com
1313  General Category / General Discussion / Re: Breadboard Schematics on: April 24, 2012, 04:56:36 am
Hi,
   You could just use different coloured single strand wire and a craft knife to build your bread board circuits neatly in the first place. It also makes it much easier if you want to transfer a design to permanently soldered strip board.

Take a picture of a neatly laid out bread board and everyone can see what you actually have wired rather than what you think you have wired.

Not the best example -
http://4.bp.blogspot.com/-KxIrcYmBxvE/T3iaO5elDeI/AAAAAAAAAS4/YzUyhlgzsPA/s1600/ConnectServo.PNG

Its a lot neater than multi coloured flexible jumpers all over the place and if you stick with a convention like green for ground, red (yellow in my case) for power and white for signals its pretty readable. It takes seconds to measure off a piece of wire, cut it then roll it with the craft knife blade to strip it, it can be transferred straight to strip board for a permanent project or put back in your box for your next bit of bread boarding.

It is of course no substitute for schematics, but if you want help with something you have built, its the best/only way of communicating what you have built rather than what you think you have built.

Duane B.

rcarduino.blogspot.com
1314  General Category / General Discussion / Re: Sinclair Spectrum 30 years old on: April 24, 2012, 04:41:51 am
Hi,
   Games were a problem, but some of them were very good, especially the Konami catridges - Yei Ar Kung Fu, Road Fighter, Kings Valley etc. Getting all nostalgic now and going to have a reminisce on youtube.

Duane B

rcarduino.blogspot.com
1315  General Category / General Discussion / Re: Sinclair Spectrum 30 years old on: April 24, 2012, 04:07:26 am
Hi,
   I was one of about 6 people who bought an MSX. Mine was a Sanyo, but you could also get Sony, Mitsubishi, Yamaha, Toshiba etc if you preferred. From memory the Toshiba was the most popular and also had the worst looking keyboard of any computer ever - apart from the Spectrum :-)

Duane B

rcarduino.blogspot.com
1316  Using Arduino / Project Guidance / Re: Making Small Lathe on: April 24, 2012, 04:03:00 am
Hi,
   A lot of 'rock crawling' radio controlled models use what are called 'lathe motors' I assume these are motors that would have traditionally been used in hobby lathes. If you look around any RC Store focused on rock crawling, you will find lots of DC motors with detailed torque and rpm specs. They can also be powered through electronic speed controllers, you could get a motor and speed control for around 30 Usd. There are also 2 and three speed gear boxes designed to work with these, put that together with electronic speed control and you have a lot of flexibility to handle different materials.

Some well priced motors and specs here -
http://store.rc4wd.com/Engine-Motor_c_26.html

Just and idea,

Duane B

rcarduino.blogspot.com
1317  Using Arduino / General Electronics / Re: op amp audio amplifier circuit help/suggestion on: April 24, 2012, 03:48:12 am
Hi,
   For the VU Meter as above but in different words, you use a resistor ladder to set the trigger voltage for each LED, the LEDs are each connected to the output of one the op-amps, the signal is connected to the + input of all of the op-amps. Each op-amp then has a individual reference voltage above which it will turn on and light the connected LED, the reference voltage is determined by the resistor ladder which is simply a chain of resistors connected in series between the supply voltage and ground.

As your supply is probably much higher than you signal voltage, you use a single high value potentiometer as the first resistor in the chain, this is used to adjust the sensitivity of the rest of the resistor ladder by dropping more of less of the input voltage across the pot or the resistor ladder. After this first variable resistor, add fixed value resistors to set your trigger ratios (I had mine all equal using a 10K pot for sensitivity, then 680 Ohms for each of the reference voltage resistors, logarithmic might be better). The resistor ladder is giving us our reference voltages so we connect the -  input of each op-amp to a step in the ladder. As the input signal rises and falls so each opamp will continually be comparing it to its reference input, if it goes above the reference, the op-amp goes high and lights your LED.

Duane B

rcarduino.blogspot.com
1318  Using Arduino / General Electronics / Re: 9v Battery - Arduino Uno R3 - PWR_SEL pins? Vin input - 5v output on: April 23, 2012, 10:55:08 pm
Hi,
   The board is very flexible in how you power it. If you have a supply greater than 7.5 volts, you can feed it in via the power jack or the vin/gnd pins, the on board regulator will drop this down to the 5 volts needed by the chip. This regulated five volts is also available through the 5v pin. You do not need to add any jumpers, the five volts line is simply the output of the regulator attached to vin.

Its also very useful that you can still use a USB connection for programming and serial communication when the UNO is powered through the regulator.

Lastly, 9v batteries are not a very good power source if you plan on running any other devices connected to the Arduino - check the two links in my signature for details.

Duane B

rcarduino.blogspot.com
1319  Using Arduino / Motors, Mechanics, and Power / Re: Using Servo library in a struct on: April 23, 2012, 08:57:40 am
No, but there is with the way you allocated them. When you call malloc you are simply asking for a memory space big enough to hold a servo object, this is not what is required, what you actually want to ask for is a 'new' servo object, this will create the space and call any constructor code required to initialise the space. Funnily enough, the command to do this is called 'new'.

If you know how many servos you need, just declare them the array way. You probably dont need the speed in your struct as you can use servo.readMicroseconds to get the current speed. Finally you can use C++ so you could use a class inplace of the struct, you could possibly just create a derived servo class which includes whatever it was that you wanted to store in your struct.

Duane B

rcarduino.blogspot.com
1320  Using Arduino / General Electronics / Re: What chips to use????? on: April 23, 2012, 08:51:21 am
Its a fair comment from the OP though, until you know there are 'decade counters', 'quad op amps', 'darlington drivers', 'dual timers' etc etc etc it really is very hard to know whats out there or where to start.

I guess the best option is to start from the project you want to build and work back from there learning what you need on the way.

Duane B

rcarduino.blogspot.com
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