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1  Using Arduino / General Electronics / Re: Pressure sensor (edit: Load Cell) on: November 25, 2013, 06:00:17 pm
thanks Mark, that's kind of a bummer, and probably costs more than it's worth. I was hoping I could use that sensor diaphragm to make water pressure sensor (for deep diving).
2  Using Arduino / General Electronics / Re: Pressure sensor on: November 24, 2013, 03:23:50 pm
Thanks Lefty, so I was searching for the wrong thing, that's why I couldn't find anything. "load cell" was the magic word.
Great explanation, thanks for the help ;-)
3  Using Arduino / General Electronics / Pressure sensor (edit: Load Cell) on: November 24, 2013, 02:29:39 pm
I got this pressure sensor from an old electronic kitchen scale, and I found no info about it on the internet. There are 4 sensors like this in a kitchen scale (even the modern one I just bought a couple of months ago), connected to the feet that hold the scale's weight.

Anybody know how this is called, so I can find out how it works? Or even better, does anybody know how it works?
4  Using Arduino / General Electronics / Re: Arduino signal amplifier Array on: November 23, 2013, 05:36:04 pm
After posting on any forum...I almost always find the solution by myself, and then I always think I should not have posted, but doesn't matter how hard I try, I only figure it out after posting smiley

Mark, you are 100% right, it's not the current sunk by the inputs. Indeed, the datasheet says that L298N only draws 100μA max per input when it's under heavy load.

I have assumed that because the Atmega chip went crazy only when the motors were running, particularly when all 4 were running.

Also, Grumpy_Mike you were right too smiley You guys are good. The issue was the inductance of the wires powering the motors. After adding the last motor to my test submersible ROV, I also thought about taping all wires together to clear the mess. The wires from the gyro that was installed on the ROV were going back o the arduino, and after I taped them all together the issues started happening. I only noticed them a couple of days later, so I didn't connect the dots.

Thanks a lot!
5  Using Arduino / General Electronics / Arduino signal amplifier Array on: November 23, 2013, 01:58:45 pm
I have two motor control boards that use L298N. They now control 4 x 3A motors.

Arduino output is connected directly to the L298N input. It works but, ocasionally the current sunk by L298N's inputs is too much for the Atmega328 chip and it passes out smiley And either stops sending serial data, or stops reading inputs, or gets stuck ouputing the same PWM values on all PWM pins.

Now I thought the best thing is to put a small NPN transistor on each Atmega328 output, but then I saw there are a lot of transistor array chips on the market (yep I'm a newbie), and I bought a few ULN2803A. They were cheap, and had 8 inputs, 8 outputs. When I got around to testing them, I found out they SINK current. So...I cannot use them (or can I?)

My question there any other good (and cheap) chip out there that works like an array of high-side darlingtons?

Or...what's the proper way of amplifying all outputs from Arduino (preferably with a single transistor array chip, to save space on the board, time and money).
6  Using Arduino / General Electronics / Re: Motor driver not working with signal from Arduino on: November 07, 2013, 05:01:39 pm
So, my topic was dumb.

I used an LM317 regulator for providing 5V to L298N. That worked fine when I first tested the circuit, then at some point it stopped working when I connected to Arduino, which made me think Arduino had something to do with it. I redid the wiring and everything works now.

Thank you for your support!
best, C
7  Using Arduino / General Electronics / Re: Motor driver not working with signal from Arduino on: November 07, 2013, 08:06:09 am
Hi Tom,

Yes all grounds are connected. I have checked and double checked. Indeed the long lines on the protoboard only go halfway through the board, but I'm only using the right side of the board.

I think there may be an issue with my L298 chip.

@JimboZA - there's nothing fancy about that. Just common ground, different power supplies (USB for Arduino and external supply for the board and motor driver) and pin13 Arduino going to input 1 on the driver board.

I just found out there's an issue with the board. It was working alright last night, before connecting it to Arduino, but now I tested it again and it doesn't seem to behave properly.

Thank you, I'll post back once I find out what happened.
8  Using Arduino / General Electronics / Re: Motor driver not working with signal from Arduino on: November 07, 2013, 07:05:50 am

It's the same as the solarbotics one:

Code is just blink pin 13.
9  Using Arduino / General Electronics / Motor driver not working with signal from Arduino on: November 07, 2013, 06:30:40 am
Hi Guys,

After almost a year of not touching any electronics I decided to continue the work on my ROV project. I made a L298N motor driver identical to this one made by Solarbotics:

The driver has some LEDs that show the state of the output pins and it seems to work just fine with +5V on the input pins, or even when I touch the input pins. However, it does not work when I connect it to Arduino.

The circuits share a common ground.
The Arduino board is powered via USB.
The rest of the circuit is powered by a different power supply.

I've recorded a short video to show you the problem:

Funny thing: When I plug the motor driver into Arduino (running pin13 blink) there's nothing happening. Arduino Pin 13  goes to motor driver input 1. Output 1 does not blink.
I have checked, Arduino outputs +4.8V to driver input 1.


If I touch input1 and input2 at the same time on the input board, output 1 and output 2 blink on the motor driver board along with ledpin 13 on Arduino.

This is probably some simple electronics mistake that I'm unaware of. Any ideas? Thanks!

10  Using Arduino / General Electronics / Re: Any experience with LB1641?? on: January 28, 2013, 05:09:42 am
Link to datasheet?
- MarkT, i purposely omitted the datasheet link because I thought it was kinda poor, or even wrong(for my exact model) and I didn't want to lead you into the same trap. I hoped some of you may have a better one around smiley
11  Using Arduino / General Electronics / Re: Any experience with LB1641?? on: January 27, 2013, 02:53:30 pm

Sorry for not responding sooner. I've figured it out. It wasn't the LB1641 IC, it wasn't the LM317, it was my power source. I used one from a printer, and it behaved awkwardly. It had plenty of power but it was the "intelligent" kind. I've replaced it with an industrial power supply and everything works perfectly again.

Thank you!
12  Using Arduino / Motors, Mechanics, and Power / Re: LB1641: Bidirectional Motor Driver with Brake on: January 25, 2013, 05:20:10 pm
Ha, works. It wasn't the diode, it wasn't the capacitor, it was my power supply. I used an old printer power supply that outputs 32V, and a LM317 that gets that down to 12V.
I swapped that for a 12V industrial power supply and now everything works and the world makes sense again. The Capacitor reduces noise, and the diode controls how much current flows through the IC, just like the manual says.
Your diagram with the 9V battery made me think.... It was the only thing that was different about your setup. Apart from that, everything was identical and mine didn't work.

Good progress for today! Thank you so much!
13  Using Arduino / General Electronics / Any experience with LB1641?? on: January 25, 2013, 11:29:45 am
Hi Everybody,

Does anybody have any experience with LB1641 motor driver? I'm following the datasheet but can't seem to get it working.
Please see the attachment for all the details about my setup. Am I missing something??? The datasheet for this one seems to be very poor in explanations and I'm not so skilled as to interpret the logical circuit and figure out what the heck smiley

14  Using Arduino / Motors, Mechanics, and Power / Re: LB1641: Bidirectional Motor Driver with Brake on: January 25, 2013, 11:27:09 am
Hi, Actually I'm having issues with that exact IC. I think I'm doing everything by the book (well, PDF).
Please see the attachment for all the details.

Can you suggest anything?
Thank you!
15  Using Arduino / General Electronics / Re: Pin13 to Darlington and motor barely spins. on: January 17, 2013, 07:09:24 am
Hi everybody,

thanks for the help

@oric_dan - I've read my posts and I see I wrote a bunch of shit there  smiley It was pretty late at night. I've edited the first post (first boggle sentence). I agree didn't make any sense whatsoever.

As far as the second thing you quoted YES, exactly. I meant Emitter and ground. First I had it between emitter of Q3 and ground, then I moved it between collector of Q3 and +24V.

Secondly, as elsewhere noted, a 3 transistor Darlington probably has too much gain for life in this universe.
I agree. I tried adding the second 2N5551 because it appeared there wasn't enough gain with only one, to saturate BD243C. When I added the second 2N5551 and I got the same result I knew I messed up somewhere, and that's when I posted here.

It would also help to know how much current the motor draws when running flat out.
It draws 70mA with no load.

@JimboZA - link doesn't work, sorry.

@michinyon - Makes absolutely perfect sense, thank you!
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