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1621  Using Arduino / Motors, Mechanics, and Power / Re: How to control arduino from the RC car battery on: February 09, 2012, 06:41:41 am

   Its very easy if you have more then 7.5 volts available, you just have to connect the battery to the vin and gnd pins. I don't have an Arduino in front of me at the moment, so I may have the name of the vin pin wrong. But I can tell you that I run my Arduino from the LIPO battery in my RC Cars this way. If your car runs from 4 AA Batteries = 6 volts, you will not be able to take this approach, in this case my first suggestion would be to power the Arduino from a 9v PP3 battery.

Duane B
1622  Using Arduino / Installation & Troubleshooting / OptiLoader Help ! on: February 08, 2012, 12:26:02 pm

    I am having no success using optiLoader to program an ATMega8, the process is failing here

result = spi_transaction(0xAC, 0x53, 0x00, 0x00);

based on the following output -

OptiLoader Bootstrap programmer.
2011 by Bill Westfield (WestfW)

Target power on! ...
Starting Program Mode...spi_init done...spi_transactionspi_waitspi_waitspi_waitspi_wait...Done - Failed, result = 0x0

Target power OFF!

Type 'G' or hit RESET for next chip

anyone got any ideas ?


Duane B

1623  Using Arduino / Installation & Troubleshooting / Re: ATMega8 No Crystal on: February 08, 2012, 11:06:02 am
Well, if no one is going to stop me, there is only one thing to do.

Fingers crossed !

1624  Using Arduino / Installation & Troubleshooting / ATMega8 No Crystal on: February 08, 2012, 07:45:35 am
   I would like to progam an ATMega8 to run without a crystal. I am reasonably confident that I can set up my current UNO to act as an ISP with optiLoader, which conveniently has an image for an ATMega8 boot loader built in.

   Looking at the ATMega8 datasheet I see that I would need to change some of the fuse settings to get it to run from an internal 8Mhz oscillator.

   Looking at the optiLoader source code, I see that the current fuses are set as follows -

during programming - 0x3F, 0xBF, 0xCC, 0, 0

after programming - 0x2F, 0xBF, 0xCC, 0, 0

However I have not been able to work out why there are apparently 5 bytes here.

I am making the dangerous assumption that the first two bytes are the low and high fuse bytes ?

From there I am going further out on a limb -

By using the fuse tool at this link I have attempted a configuration for the 8Mhz Internal Oscillator which gives me 24,BF for the low high fuses.

Can anyone confirm that my approach is correct and review my fuse settings ?

Your help is very much appreciated,

  Duane B

1625  Using Arduino / Microcontrollers / Re: Rapid switching capabilities of Arduino? on: February 08, 2012, 01:34:11 am
   I built a 555 based transmitter yesterday, its very easy and potentially allows you to put more power through the IR Emitter LED for more range, it also frees you from having to wire the emitter to the Arduino making most applications a lot more practical. Its also a bit of a novelty getting some hardware to do some of the work for you.

   I am powering the IR Emitter directly from a 9V battery or a 2 cell lipo. As 555s are so cheap, pick up a handful or two and have a go, I used an online calculator to get the C,R1 and R2 values I needed for a 40Khz carrier signal that could trigger an IR Receiver.

   Here is a link to the calculator

   Here is a nice link to some 555 timer applications, the circuit you want is the AStable

Duane B

1626  Using Arduino / Project Guidance / Re: feasability for arduino project on: February 07, 2012, 11:10:40 pm
    Sounds like a nice project, I used to build slot cars from resin kits, never raced them though.

    One thing I used to have was a scalextric pace car system, It basically recorded your best lap then replayed it constantly so you could race another car against your own best lap.

    I still enjoy building the slot car kits but spend most of my time on RC Cars now.

    Duane B

1627  Using Arduino / Installation & Troubleshooting / Re: Can I Use UNO To Program ATMega8 bootloader ? on: February 07, 2012, 10:11:53 am
   I think I have it now, based on your response and some subsequent searching -

When you upload a sketch, you're using the Arduino bootloader, a small program that has been loaded on to the microcontroller on your board. It allows you to upload code without using any additional hardware.

I will have a go at using optiLoader to put a boot loader on the ATMega8, I assume I can then put it into the UNO in place of the ATMega328 and upload test sketches.

Assumming this goes to plan I want to have a go at configuring the fuses to use the internal oscillator for some low cost projects.

Thanks for the pointers,

Duane B
1628  Using Arduino / Installation & Troubleshooting / Can I Use UNO To Program ATMega8 bootloader ? on: February 07, 2012, 08:35:04 am
    I have read through several methods of getting the bootloader onto an ATMega8 using the UNO as and ISP, but why can't I just put the ATMega8 directly into the UNO and select 'Arduino NG or Older with ATMega 8' as the board in the tools/board menu of the Arduino IDE ?

Thanks for any help

Duane B

1629  Using Arduino / Project Guidance / Re: IR Endurance on: February 06, 2012, 01:55:29 pm
Thanks for the responses. There is very little chance of finding a data sheet in the shops I have access to. Dubai may have the worlds tallest tower, but component shopping in 'Old Dubai' is quite literally an adventure.

I have just moved the circuit from bread board to strip board and dropped the current limiter to 330 in the process, on your advice I could still go lower, but will see how this works out for now.


Duane B

1630  Using Arduino / Project Guidance / IR Endurance on: February 06, 2012, 11:53:58 am
   I am using an IR Led pulsed at <>70hz with a carrier of <> 40Khz. Its driven with 9v and a current limiting resistor of 470 Omhs, the carrier and pulse are generated through chained 555 Timers.

   Assuming the circuit is active for hours at a time will the IR LED survive in the longer term ?

   If not, can anyone suggest an alternative approach to providing a persistent IR Signal ?

   Thanks for any help
1631  Topics / Robotics / Re: maximum number of servos? on: February 05, 2012, 03:25:57 am

Read this,

Then this

The Uno can drive 12 servos, thats twice the six you have asked for and in doing so it uses only 1% of its processing power, I was both surprised and impressed when I measured this.

Duane B

1632  Using Arduino / Project Guidance / Re: Acceleration from wheel speed - code examples? on: February 05, 2012, 12:32:15 am
    I received and replied to the PM, I know that PM's were not working recently, so if you don't get it, let me know here.

Duane B
1633  Using Arduino / Project Guidance / Re: Acceleration from wheel speed - code examples? on: February 04, 2012, 04:50:19 am
   As you know from my blog, I have used the Arduino to measure the wheel speed on my RC Cars, the wheels generate a single pulse once per revolution giving me a maximum rate of 68 pulses per seconds. I expect the same code would also work for you and your much higher frequency pulses however it may require some tuning.

Now, I think it might be interesting to collaborate with you to get something suitable running for your application, my only reservation is that I am not that excited by the end goal of the project as you have currently described it - 'I'd like to illuminate a series of LED's depending on the change in wheel speed' is there more to it or is there some higher purpose that is being served by these LEDs ?

Also how about a picture of the car and a little bit about what you use it for just because I (and others might ) am interested regardless of whether I can help out or not.

Duane B.

1634  Using Arduino / Motors, Mechanics, and Power / Performance of One Arduino with 12 Servos + Code on: February 03, 2012, 03:39:53 pm
    I recently published a blog post showing how to control upto 12 Servos with a single Arduino and the Servo Library.

    I felt the post was incomplete as it provided no indication of the performance impact of controlling 12 Servos with one Arduino.

    I have now addressed this and the results are pretty surprising -

    Its late again here, so if anyone spots any howlers, please let me know

    Duane B

1635  Using Arduino / Project Guidance / Re: Acceleration from wheel speed - code examples? on: February 03, 2012, 12:29:04 pm
   What type of sensor is it that you are using to get 40 pulses per revolution ? Its not counting spokes is it ?

   I have no idea how complex the rest of your application is but I have an idea that using a simple counter IC to reduce the number of pulses per revolution might be helpful.

   Using a counter together with an AND gate you could generate a single pulse to the Arduino for every 40 sensor pulses. There are several advantages to this -

1) The Arduino is free to do a lot more work, we have reduced the interrupt load to be 40 times more efficient
2) The code will not need to be optimised to the nth degree
3) The maths can be much less sophisticated to calculate frequency (revs) and the rate of change from a single pulse per revolution

Duane B
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