Yes, the regulator returns to 6V when disconnected. At least this isolates the issue to something in the H-bridge. The 5V rail is currently only wired up to the driver enabling pins (as a 5V digital HIGH) and the power source for the internal circuitry in the bridge (Vcc1).

I can't get you a clear photo as my wiring is an eyesore - ribbon wires are great on one end, but on the other they're horrific... (It's a PCB prototyping board, so no neat traces here).

There is one thing, which I think isn't the issue, but I'll put it forwards regardless - the H-bridge has 2 ground/heat sink pins on each side, and the regulator ground is connected to one of these pins. This pin does not go directly to ground, but the one on the other side does. This shouldn't be an issue, correct? A continuity test on a multimeter shows they're connected.

Does the 3.3V when connected indicate a ground continuity issue? It's almost as though the other regulators are affecting it in some way...

Thanks for the heads up, I'll incorporate one. But it still doesn't explain the voltage drop

If I assume everything is wired perfectly, is this normal? Because all I can think of right now is that something, somewhere, is connected to the wrong thing, but if this is a normal (albeit bizarre) thing to be happening I can just go with it.

Fritzing does not do schematics, it does physical layouts which are useless for fault finding.

From you description I see there is no mention of input or output capacitors for the regulator. These are needed.

Fritzing has a circuit schematic viewmode that, although basic, does the job. Want me to create one?

As for input/output capacitors, here's a quote from the datasheet: "No External Components Required" which I assume to mean that no filter capacitors are needed.

If you install the latest version of Optiboot provided by @westfw you should not need to do anything special (like cutting the RESET trace) for the Arduino ISP Sketch to work.

However you would have to re=enable the trace path for when you want to do future uploads of other sketches onto the board, or learn how to time manual resets at the proper time to allow uploads to work.

@Coding Badly, I have no way to update my Uno as of yet, so I plan to purchase an additional 328 for the purpose (also for a standalone project I have), which is why I need to run ArduinoISP on my current Optiboot.

@retrolefty, as the trace is designed to be cut (it's one of those bare pads) I can easily re-solder the joint to enable the functionality again.

As the Uno (with default Optiboot) seems to have trouble flashing through ArduinoISP because of autoreset problems, could I slice the PCB trace that enables autoreset and then flash using it?

You have an h-bridge chip for each motor?
The 7806 is getting hot to the touch? Your 10V source can put out enough current for all the regulators?
If not, how are things wired?
Are the motors enabled when this happens? Does it happen when they are disconnected?
Post a schematic please.

I'm off to bed ...

I have 2 bridges for each motor, for bidirectional control.
My 10V source can output 1A, so is enough. Remember, it was working fine before the 6V regulator was attached, the 3.3 and 5 provided power wonderfully.
All of the regulators are getting warm, but I think it's due to stepping down the voltage as opposed to current draw (as measured current draw for entire circuit was 150mA)

As for wiring/circuit diagram, I'll do my best to explain, but can whip up one it Fritzing if you wish.

10V source (Vin) connects to Vin on Arduino, 5V regulator, 6V regulator, 3V regulator. Grounds are all linked.
According to datasheet for H bridge, 1,2EN 3,4EN Vcc connected to 5V regulator output.
Ground/heatsink connected to shared ground.
1-4Y currently disconnected as no motors present.
1-4A connected to 8 Arduino pins, half PWM, half digital. Default LOW.
Vcc2 connected to 6V regulator output.

3V regulator connected to 4x 300ohm resistors in parallel, then to ground.

I hope that's enough information, again, I can get something up in Fritzing if you wish.

Hi all,

I'm currently creating a Arduino controlled laser spirograph, that has 4 motors attached which I'm controlling through an H-bridge. My problem is that upon attaching my 6V regulator (instead of my Vin which is 10V) to the Vcc of the H-bridge, the voltage output of the regulator drops to about 3V. I didn't have this issue when it was wired directly to Vin, and when the regulator is attached to nothing ouputs 6V.

I know that something is wrong here and that it's my fault, I just can't find it. I've tested almost every contact in the entire circuit looking for shorts and can find none. I've triple checked the data sheet to make sure it's wired correctly, and I still can't find where I've gone wrong. The circuit also contains a 3.3V and 5V regulator, both of which are functioning correctly, however when the 6V is connected to the bridge, they drop about 0.2V each. Measuring the total current draw with the 6V attached, it came out to only 150mA, which is in line with 40mA of pots (they're low resistance) and a 7 segment display.

Basically, I'm completely flummoxed as to the problem. Does anyone have some additional troubleshooting tips that could help?

Regards,
Will

P.S. Here are the datasheets for the 6V regulator and the H-bridge.

That fixed it... Seeing as the other function worked fine, I assumed it was something like that, just never thought to put it before loop(). Thanks!

Strangely, a helper function actually calls writeString("TEST") at one point and it compiles fine! More to the puzzle...

Hi all,

I'm trying to write myself a function with optional arguments, and DO NOT want to use function overloading as it seems nonsensical in this case. I've tried to do it the normal way:

Code:

void loop() {
  writeString(String(selectedPattern));
}

// Given a string, this will write it to the display.
void writeString(String str,int delayTime = 0) {
  int StringLength = str.length();
  if(StringLength > 4 || StringLength == 0) return;
  for(int i=0;i<4-StringLength;i++) {
    Serial.write(0x78);
  }
  for(int i=0;i<StringLength;i++) {
    Serial.write(str.charAt(i));
    delay(delayTime);
  }
}

Compiling this, however, gives this error:

'writeString' was not declared in this scope

What am I doing wrong here? This is driving me nuts! I don't want to do function overloading as it's messy and takes up more space (for a single line of code too!) Removing the delay() and the default value in the call fixes it (but breaks it in another section where I define a delay).

Excellent, thanks for the clarification. I think I should be right using the 360 ohm resistors then - I probably have some laying around somewhere...

Thanks again!

Will

How about putting a high-side resistor on the pots such that they form a voltage divider with approx 1v at the junction. Then use the internal 1v1 reference.

______
Rob

I'm not 100% sure I understand - so put an appropriate resistor so that the highest voltage is 1.1v between 5v and the left pot pin?

Aka

5v----resA-----1.1V here----100ohmPot-----0v (middle pin goes to A0)

Calculate resA=354.545 ~ 360ohms

That's still 10mA per pot - is it small enough?

Also because my brain is refusing to cooperate, is that one 360 ohm resistor per pot or one for all four? Is a resistor fine to cope with 40mA? Pretty sure, but want to check...

There is no easy way to do this.
Probably the best way is to wire the + end of the pot to a PNP transistor then to +ve and only switch on the current to that pot while you make the measurement. In that way there is only one pot connected at any one time and only breafely at that.

Sadly I don't have enough ports for that - 4 switches, 4 pots, 8 motor control (motors go both ways). I'm just glad that someone's confirmed it for me so quickly - it's too difficult. Thanks!

Hey all. 

I'm slowly getting through a laser spirograph project that's controlled by an Arduino (save/load patterns etc  ) and I have 4 100ohm pots that I'd like to use for controlling the speeds of the motors. Now, I bought these because originally I planned for this circuit to be completely analogue - they're wire wound and can take up to 2W, which is perfect for driving motors, but now I'm using the Arduino I'd love to adapt them for it.

A single one works fine with the standard setup for a pot, but of course because this is only a 100ohm pot it constantly draws 50mA from the Arduino (on the 5V output). This isn't desirable at all, especially since I need 4. I've tried several combinations of resistors with the analogue reference pin and the pot itself, but so far haven't got anywhere useful.

Is there an easy way to make these draw less current? I'd love to not have to buy 4 more, however cheap they are. I'm quite poor at the moment  I've tried making the overall voltage drop less and changing the analogue reference, but I've been having issues with it.

Thanks in advance!