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1  Using Arduino / Networking, Protocols, and Devices / Arduino UNO to DUE Communication via Serial on: July 21, 2014, 04:00:55 pm

I am wondering if it is possible to using a USB-B to Micro USB cable to communicate between the UNO and DUE via the programming ports. I don't see how it is an issue (other than debugging of course). I haven't tried it yet, but I do want the community's opinion.

2  Using Arduino / General Electronics / Re: LED Over Current Indication: Circuit on: December 05, 2013, 10:20:38 am
Hello LarryD,

Thanks for getting back to me, I was looking at comparators and high-side current sensing, but this seems like an easier implementation.

Rather, I would prefer once the fuse is blown there is no more current feeding through the load. 

I cannot think of how to modify your circuit to get what I want.  Are there types of fuses that will act like a switch when triggered?

3  Using Arduino / General Electronics / LED Over Current Indication: Circuit on: December 04, 2013, 11:46:33 pm
Hello Community,

For my project's power supply circuit, I have as 12V  source going through a fuse before going into the regulator.

The fuse is set to trigger at 3A.  When this occurs, I want have an LED to indicate over current draw.

I was wondering what would be the best solution to do this?

4  Using Arduino / General Electronics / Re: Arduino DUE: max current from Vin pin on: December 04, 2013, 12:16:54 am

I have a similar inquiry.

I want to understand the small circuit before the regulator which includes diode D1 and the ferrite bead. 

Comparing the Due to the Uno, D1 is now parallel rather than in series, so current pull should not depend on the diode (correct me if I am wrong).  Rather, between VIN and the Power Jack is the ferrite bead rated at 3A.

Going back to D1, I see that if there is a reverse voltage VIN and GND become shorted which is scary to me, but I guess it saves the electronics - but may destroy your power supply.

Now to summarize, assuming that power is wired correctly. VIN pin should be able to source 3A.

I am developing my on motor driver board so I am trying to understand if developing external power is necessary or I can just use VIN.

If there is anything I said wrong, please correct me.

5  Using Arduino / Motors, Mechanics, and Power / Re: L298P: Thermal Pad Connection on: October 25, 2013, 12:50:25 pm
When DC motors start from a standstill, they draw the stall current for a short period of time. If you suddenly reverse the direction of rotation, the short-term current draw is even higher than the stall current.

Hello jremington,

Yes the inrush current will a concern since the driver will not be able to provide that current, ~3.75A at 9V.  Additionally, my power supply is not rated for the inrush current.  I will need to develop a current limiter or just add a resistor to enable a soft-start.

6  Using Arduino / Motors, Mechanics, and Power / Re: L298P: Thermal Pad Connection on: October 25, 2013, 10:55:48 am
It's unusual to power motors from a regulated power supply.

Yes I agree with you. For my application, I am using a custom battery and it is important that I maintain a constant DC external motor supply.  Regulating the 12V to 9V with a low-dropout high-current voltage regulator should do the job.

However, the stall current is quite high, looks like it will be about 3.75A @ 9V. So I suggest you either use both channels of one chip in parallel per motor, or (if you do not require the full torque), connect a low-value resistor in series with each motor to limit the current. It's probably also a good idea to use soft-start.

I doubt I will ever get close to the stall toque, but just to be same I will nonetheless use one driver for one motor. More current capacity cant hurt anything.

Again dc42, thank you for your suggestions.

7  Using Arduino / Motors, Mechanics, and Power / Re: L298P: Thermal Pad Connection on: October 25, 2013, 09:39:55 am
The L298 has a voltage drop of 2.55V typical, 3.2V max @ 1A. So at 800mA load, each L298P will have to dissipate around 2W, perhaps even 2.5W. You will need a lot of PCB area fanning out from the thermal slug to get rid of that heat. Even if you solve that problem, you will need to provide a higher battery voltage to allow for the voltage drop.

dc42, I appreciate your suggestions and I believe I will be switching my driver based on what you have provided me.  I did not know that there such a significant voltage drop on the L298 that would contribute to heat production.  I am assuming you calculated that 2W from 2.55V (voltage drop) * 800 mA current draw = 2.04W dissipation.

If the VHN5019 has too many legs for you to solder easily, how about using the TB6612FNG dual motor driver, if your supply voltage is 13.5V or less? It can drive 2 motors at up to 1.2A continuous, with a typical voltage drop of 0.4V @ 800mA. So you will only have to get rid of 1/6 of as much heat compared to the L298. You could connect both channels in parallel for even better performance.

I am powering my system through a 9V regulated from 12V battery supply, so the TB66 seems efficient enough to drive the motors.  The motors in particular is linked below:

As you see the current draw is low and with the torque provided, my application will not load much further than 2-3 times the free-running current.

btw if you have been hand-soldering the VHN5019, then I strongly recommend that you look into other SMD soldering techniques. The hotplate method is a good place to start.

The pin count isnt the biggest trouble for me.  My first revision of the board, I really didn't think about how I will solder the thermal slugs located on the bottom of the chip.  I did not know about using vias to feed in solder from the bottom. I had to use a hot air gun with solder paste to attempt to get this to work.  It was a large mess and it kind of forced me away from the chip.  Our lab has no other tools, like a reflow oven to appropriately do this. I like this TB66 because it seems to be efficient without a thermal slug.

Additionally, I am using the Arduino Due, and the TB66 seems to allow CMOS level operation voltage (>2.7V).

Something is concerning me, the breakout board doesn't have fly-back protection diodes, and the datasheet doesn't specify that it is included.  I am sure they are necessary.

Thank you for your suggestions, I appreciate them.

8  Using Arduino / Motors, Mechanics, and Power / Re: L298P: Thermal Pad Connection on: October 25, 2013, 08:02:25 am
I don't know the answer to your question, but if you are building your own board using SMD components, why on earth are you using an L298? There are lots of mosfet-based SMD motor driver chips available that are far superior to the L298. In particular, they have much lower voltage drop (and therefore they generate much less heat), and most of them have built-in current limiting.

The first revision of my board utilized the VNH5019, I found those to be extremely efficient but also pretty tedious in soldering them.  I hear a lot of horror stories with the L298 being a fat power dissipating radiator of heat.  Fortunately for my application, I hooked up the L298's H-Bridges in parallel boosting up my current capacity, hoping this will keep the driver and a decent level of heat. Essentially each motors is being driven by one L298.

For my application, I do not expect these motors to pull anywhere past 600 mA - 800 mA of current. With the L298 being use in parallel, it can output 4A, this is giving me the OKAY to use these chips.  Unless you have another reason in which I haven't looked into, I want to use the L298 for it's simplicity.

Any suggestions?

9  Using Arduino / Motors, Mechanics, and Power / L298P: Thermal Pad Connection on: October 24, 2013, 03:44:40 pm

For the L298 motor driver, I see that there is a tab used to attached a heat sink to. 

The L298N (vertical standing) and L298HN (horizontal laying down) have a tab that is connected to GND (Pin smiley-cool of the chip.  When it comes to the SMD package (L298P) it doesn't state if the thermal pad is GND.  I see pictures that the L298P has a thermal pad but the datasheet doesn't a) show it and b) indicate its connection.

Does anyone have experience with this specific chip that can help me out?


10  Using Arduino / Motors, Mechanics, and Power / Re: Boost-Up Current Limit: L298N ...? on: October 10, 2013, 10:56:26 am
Note that when you do this (and actually, any time you go over about 1 amp on the L298) you're going to need a fairly beefy heatsink. The L298 is anything but efficient...


Even with loading, I doubt my motors will exceed 1A, but my board will consist the SMD package with the thermal pad.  I hope have a fairly large ground plane to dissipate heat as well as perhaps attach a small heat sink on top of chip.


11  Products / Arduino Due / Arduino Due: Using Analog Pins for Digital I/O and External Interrupt on: October 10, 2013, 10:35:44 am

I would like some confirmation on the Due regarding the Digital I/O.  I know that the AVR boards allow the analog pins to be configured as digital IO, but how about this Due?  I am sure it can, I would just like some confirmation.


If the former is true, can you attachInterrupt() on these pins?

Are there any concerns regarding the use of analog pins as digital IO and external, such as speed?

12  Using Arduino / Motors, Mechanics, and Power / Re: Boost-Up Current Limit: L298N ...? on: October 09, 2013, 08:12:01 pm

Thank you, how couldve I missed that!

13  Using Arduino / Motors, Mechanics, and Power / Boost-Up Current Limit: L298N ...? on: October 09, 2013, 03:01:50 pm
Hello Community,

For my project, I would like to dedicate an L298N for a single motor.

I understand that the L298N has a dual H-bridge at 2A current source.  How would you pin the L298N to dedicate both H-bridges to one motor?

Does it cause any issues to be aware of?

Thank you,
14  Using Arduino / Microcontrollers / Re: Arduino Due on a Breadboard? on: July 18, 2013, 12:06:19 pm
I'm curious, what was your objection to just using the teensy 3?

Bill,  I don't see a difference between the Teensy and the Arduino Due, other than the Teensy has a footprint where you can pop it into a breadboard.  The chip is still soldered down and you cannot use this platform to externally program a SAM3 that I want to embed into my custom board.

My goal is to create a board using a SAM3 and use the Arduino IDE to compile my sketch onto it. The Teensy breadboard footprint is good for prototyping, those stages are complete in my project.


15  Using Arduino / Microcontrollers / Re: Arduino Due on a Breadboard? on: July 18, 2013, 12:02:32 pm
is it possible to hook up the Arduino Due to these pins and compile code to the SAM3X on the custom board, rather than the chip on the Due?
I'm not quite following I think. Do you mean pass the Rx/Tx through from the Due to your board?
That might work if you manually erase the SAM first (you have implemented the erase feature with the push button or something I assume).

I can probably sacrifice my board and remove destroy the connections that go to the chip on board,
I don't get this.

The video at the top of the thread shows how to compile your sketch onto an external ATMEGA328 using the Arduino Uno board. He removes the chip from the board, places it on a breadboard and was able to compile the code by passing the Rx/Tx lines from the board to the chip on breadboard.

I would like to do the same with the Arduino Due and the SAM3, but this seems to be troublesome because the chip on the Due is soldered on.  My question is how can I program an external SAM3 using the Arduino Due.

If it is possible to somehow by pass the chip on the Arduino Due, and pass the Rx/Tx lines to a bootloaded SAM3 on a custom board, this would be ideal for me.

Another possible solution would to get an ARM-type external programmer that is compatible with the Arduino IDE and bring out the ICSP pins from the SAM3X.
That's more like it, implement the JTAG/SWD header and buy a cheap programmer.

Another way is to run your Rx/TX to a header and buy a Taigiuino programmer.
This would be my preferred method I think.

I will look into this, I have no idea the JTAG header does but from previous research, it looks like this will need to be used to compile code onto the chip

You should also implement the erase function, have a look at their schematics for their Due clone

How would this help me ?

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