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1  Using Arduino / Project Guidance / Re: Referencing grounds and a RC power supply on: July 28, 2014, 05:09:56 pm
Your post seems to be missing the images, or I'm having and issue and can't see them...

I've attached the images to the post.  Hopefully that will help to illustrate my questions

If the "ground" is not really grounded, you can connect power supplies in series.   You need to check the specs or test it with an Ohmmeter (multimeter).   There should be no connection (infinite resistance) between the power supply's common/black/negative connector and the chassis, or between it and the common/black/common on the other power supply.

That's the idea here.  The tutorials that I've read will completely isolate the ground on the output (DC) side from the AC side.
2  Using Arduino / Project Guidance / Referencing grounds and a RC power supply on: July 28, 2014, 12:26:33 pm
I have recently converted a Server power supply to use as a "bench" supply to charge my RC Multicopter batteries.  Here is the tutorial that I've followed to make the my current 12v version I've been working on a circuit board (labeled "supply interface" below) to replace the one that is removed in the tutorial.  I'm hoping that the supply interface would enable me to use a Arduino Mega with a TFT shield to operate a few of the controls and monitor temperature.  The mega would communicate with a arduino mini located on the supply interface.  

My goal is to control two supplies running in series as outlined in the tutorial for a 24v supply.  Once I started to think about how the two supplies and all of the control stuff would be connected I really started to wonder about grounds.  Here is a block diagram that got me thinking:


On the left is the mega, in the middle is the supply interface, and on the right is the power supply.  Starting simple, if I maintain two grounds on the interface for the second power supply like this:

Would that keep the two grounds isolated without causing any problems while maintaining the ability to run the supplies in series?

Then as a follow on question is it possible to add a digital pot (controlled by the mini) between +5 from the power supply and the VOLT_ADJ pin, as well as read the speed of the power supply's fan without complicating things too much?

Thanks a ton,

3  Using Arduino / Project Guidance / GPS Follow me module... Is it possible on: April 01, 2014, 01:52:09 pm
I've got a hexicopter that I am beginning to shoot video with.  I'd like to build a small module that I could attach to a RC plane to have my hexicopter follow.

The system would most likely be comprised of two components:
  • A transmitter module to attach to whatever moving object I'd like to film consisting of the following:
    • GPS Module
    • Arduino Fio
    • Xbee to send the info to the receiver
  • A receiver of some sort to send the GPS information to my laptop (via usb????)

On my laptop I use a program called mission planner that has a "follow me" mode.  This mode uses the onboard GPS (on a tablet or phone) or incoming GPS data to tell the drone (Via wireless telemetry link) where to go to follow the location of mission planner. 

I think that I've got a basic understanding about how to transmit the GPS info from one xBee to another.  Does this seem feasible?  If so where could I find information of how to format and parse the location data to something that Mission Planner could use?


4  Using Arduino / Networking, Protocols, and Devices / Re: Trying to get RSSI Value... How do I troubleshoot this on: March 20, 2014, 10:27:09 am
Would there be a way to include an if statement to check for High if there isn't an RSSI signal?


What about this:

int rssi1= pulseIn(rssiPin, HIGH, 300)/2;  //Read a HIGH pulse on a pin
      if (rssi1 == 0){
        if (digitalRead(rssiPin) == HIGH) rssi1 = 100;
if (rssi1 != 0){
        //use rssi value

5  Using Arduino / Networking, Protocols, and Devices / Re: Trying to get RSSI Value... How do I troubleshoot this on: March 20, 2014, 09:55:09 am
Sorry to dig up an old thread, I am having a similar problem and thought this would be a good place to start.
 Is there a work around available for this problem?

Many thanks all

No worries about digging this up.  One thought that I had was to check for RSSI and if there wasn't a duty cycle to check to see if the RSSI pin is high.  If it is high then could you assume that your rssi is 100%  I'm not an expert, but it is an idea I had.  Anyone have any comments as to why this might or might not work?

6  Using Arduino / Project Guidance / Re: help with a 232 circuit. on: February 21, 2014, 07:00:51 am
I think I used the sparkfun site as a guide.  This is what I based my circuit off of:

Are you saying that I need to add another cap between pin 6 (+) and gnd (-)?


7  Using Arduino / Project Guidance / help with a 232 circuit. on: February 20, 2014, 09:04:29 pm
I've got a Radio for a RC multicopter that can output rs232 information from the muticopter.  I connected it to my arduino through a TTL converter and this: library, low and behold I was getting information from my copter.   I'm also using a Xbee to get some info too.  So I decided to create a shield. 

Attached are pictures of the schematic, layout, and the actual shield.  Currently the shield isn't getting the information to the arduino correctly.  I've missed important details in some previous projects.  The first question that I have is did I orient the caps the right way on the actual shield?  If that isn't the issue then the next question is when I run this code inside my sketch:

  if (Serial2.available()) {
    char c =;
    //Serial.println("Stuff from TX");
    //if (frsky.update(c)) { // frsky_update() returns 1 if a complete packet was successfully decoded, otherwise 0
    Serial.print("TX RSSI: ");
    Serial.print("Telemetry RSSI: ");
    Serial.print("RX Voltage: ");
    Serial.println(frsky.getRX_a1()*0.0517647058824); // The internal sensor has a 4:1 divider, so the value is 0-13,2V in 255 steps or 0,052V per step
    Serial.print("A2 Voltage: ");
    Serial.println(frsky.getRX_a2()*0.0129411764706); // A2 without divider is 0-3,3V in 255 steps or 0,013V per step

As soon as I fire up the Rx this is what repeats with the above code. 

Telemetry RSSI: 0
RX Voltage: 0.00
A2 Voltage: 0.00

When I include the if statement I dont get anything to the serial monitor.

Any input as to why the information being sent to my transmitter isn't being communicated correctly would be greatly appreciated!


8  Using Arduino / Installation & Troubleshooting / Re: communication problems with my pro mini on: February 17, 2014, 04:34:50 pm
Today I thought I would work on this a little more to see if I could find anything more.  I have the pro Mini connected like this tutorial suggests:

I've tried a bunch of things.

  • hold the reset until uploading sketch appears
  • select uno as the board
  • Burning bootloader
  • reversing Tx and Rx Pins (along with all of the above attempts)
  • Also tried burning the boot loader in windows7

The green LED still continues to blink quickly.  

Any thoughts?


9  Using Arduino / Installation & Troubleshooting / communication problems with my pro mini on: February 10, 2014, 05:56:13 pm

I've been working on a involving a processing sketch to communicate with a pro mini.  Last night while I had the pro mini connected to my computer and the processing sketch was running I tried to upload a revised sketch to my pro mini and there was some sort of conflict.  Now the pro mini isn't working properly.  When I try and use it the green light just blinks.  I know that I should have quit the processing sketch before trying to upload but I had forgotten the processing sketch was running.

Here is the error that the Arduino IDE gives me when I try and upload to the mini.

avrdude: stk500_recv(): programmer is not responding

Any help that could be provided to get me up and running again would be greatly appreciated.


10  Using Arduino / LEDs and Multiplexing / Re: So many possibilities to troubleshoot... Where do I begin? on: February 09, 2014, 04:57:30 pm
You guys are brilliant!

If you have an free pin on the controller, route it to the outside of a three pin male header.
The other outside pin could be connected to +5V.
The middle pin of the header connects to pins #7.
Place a header jumper on the +5V or controller side as needed.
In the controller position, you can send a clear.

I'll bet you are getting comfortable with your schematic drawing program, that's the way you learn.

I'll incorporate that.
11  Using Arduino / LEDs and Multiplexing / Re: So many possibilities to troubleshoot... Where do I begin? on: February 09, 2014, 04:22:38 pm
Ok, so for the next version.

Pin 7s are  floating, tie to +5 if not used.
Are you sure you don't want to use Q7 of I.C. 2?  Edit maybe you want "see image"
Thanks for the tips. 

Should I connect the pin 7s to digital pins for versatility or is it worth it to use the pins.  Right now I just have pulled them high with the VCC out of the pro mini.

Thanks again!

12  Using Arduino / LEDs and Multiplexing / Re: So many possibilities to troubleshoot... Where do I begin? on: February 08, 2014, 10:52:34 pm
I think that I have found a surface mount version that would work.  Check out the attached schematic for more details and let me know what you think.

As far as the pwm I was going to try something like this:

Let me know what you guys think.

13  Using Arduino / LEDs and Multiplexing / Re: So many possibilities to troubleshoot... Where do I begin? on: February 07, 2014, 07:53:22 am
Thanks to both of you for all of your input!

Shift registers:
Shift registers can be used in many ways, but is it useful ?
Pushing 24 bits into the shift registers is very fast. I think there is no need to change it.

I'll leave it as is then.  I think that I have a board with 4 shift registers that I can play with until I actually get this one made.

Led strip resistors:
The led strip is for 12V. Often 3 leds in series are used, with a resistor, to make it work for 12V. With a led strip, you don't need extra resistors.
This is also good news.
To get all the RGB colors, a PWM signal is used for every 'R', 'G' and 'B'.
Since you use the shift registers, using PWM is a lot harder and not so smooth anymore. Did you know that ?
I had seen it eluded to but not specificly talked about.  I think for my application I might not need the fade part, but I'll do some testing and find out.
maximum current
I see you have the 12V at the led connector, and the ULN as driver.
The ULN chips have a maximum current per output and a total maximum current.
Can you check that ? The current depends on the length of the led strip.
The datasheet for the texas instruments chip located here:
 mentions 500mA peak collector current.  Does that mean for the entire chip or per IO?

Maybe late to the game, but I would just use qty 3 TPIC6B595, in place of the HC595 and ULN2803. 150mA current sink per output, rated to 50V. 3 LEDs/strip are generally 20mA, so 21 LED strips would be supported.
There are other versions of TPIC6x595 that can sink more.
I have boards on hand already that have arduino functionality and 3 TPIC6B595s already made if you want to buy a bare board, or an assembled one.  Will post a pic  when I get home.  All thru hole, easy to assemble.

Nope not too late.  I'll do some looking and try a layout to see what I can come up with.
14  Using Arduino / LEDs and Multiplexing / Re: So many possibilities to troubleshoot... Where do I begin? on: February 06, 2014, 08:35:23 am
So I've made several more adjustments to this project.  Attached is the latest schematic.  

Check the wiring of the shift registers. Either the schematic is wrong, or you have connected them wrong.
This is explanation and shows cascading for 2 shift registers:
You have enough pins, so you don't need cascading.

Could I address each shift register individually?  If I can address each register individually are there any downsides to doing so other than using extra pins?

I'm going to be using LED strips.  I thought I saw current limiting resistors on the strip.  If they have them on the strip would it be necessary to include them on this board?

I did see that there are resisters on the LED strips.  Does anyone have a recomendation as to whether or not I should include current limiting resistors as part of this schematic?

Again many thanks everyone!

15  Using Arduino / LEDs and Multiplexing / Re: So many possibilities to troubleshoot... Where do I begin? on: February 04, 2014, 11:27:32 pm
Would placing them like this be good?

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