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31  Using Arduino / General Electronics / Potting KEMET Supercapcitors (Perhaps JamesC4S can chime in here?) on: December 29, 2013, 07:54:10 pm
Hi all,

I've got an application in which some supercapacitors are used - however, caps like the KEMET FC series, which I am using, (http://www.kemet.com/kemet/web/homepage/kechome.nsf/file/KEM_S6011_FC.pdf/$file/KEM_S6011_FC.pdf), according to the documentation should not be potted. I would however, like to pot the device for a number of reasons.

FM series caps (http://www.kemet.com/kemet/web/homepage/kechome.nsf/file/KEM_S6012_FM.pdf/$file/KEM_S6012_FM.pdf) however, can be?

So, why should the FC series not be potted, whilst the FM can be? I'd like to avoid the FM series, as nobody seems to stock them off the shelf like the FC series.

However, the datasheets says...
Quote
"2.5 Cleaning, Coating, and Potting
Except for the FM series, cleaning, coating and potting must not be carried out. Consult KEMET if this type of procedure is
necessary. Terminals should be dried at less than the maximum operating temperature after cleaning."

So, if I still want to pot an FC cap, what is KEMET likely to advise?

Many thanks in advance!
32  Using Arduino / General Electronics / Re: ST Micro MEMS Gyro Voltage Reference on: December 01, 2013, 09:59:34 am
Quote
All analog MEMS accels/gyros  I've see use Vdd/2 as the zero level and the
signal varies above and below this - Vdd of the sensor is the voltage to use as AREF.
I think most are also ratiometric so you don't have to compensate for the supply
voltage even.

This is how I've implemented the device, and simply left vref disconnected. I may modify the board to have the vref on a test pad with the mask exposed just to measure it out of interest.
33  Using Arduino / General Electronics / Re: ST Micro MEMS Gyro Voltage Reference on: November 29, 2013, 06:03:07 pm
My thoughts exactly, but no way of knowing from the datasheet... Strange for newish ST devices...

The zero rate output sits at 0.5Vcc and swings either side to the rails, so surely the Vref is just the max output voltage.
34  Using Arduino / General Electronics / ST Micro MEMS Gyro Voltage Reference on: November 29, 2013, 09:57:23 am
Hi all,

I'm looking at using one of ST's MEMS gyros, however - unlike most of their parts, the datasheet is quite sparse on info. Here's the datasheet http://www.st.com/st-web-ui/static/active/en/resource/technical/document/datasheet/CD00254111.pdf

The part is an LY330ALH, which is an analog gyroscope. However, there is a pin on the device VREF, with very little information about it. Page 11 shows an outward arrow from the pin, so I presume it's a voltage reference used for ADCs, but nowhere does it mention what value it is.

In the documentation for an eval board, (one which I cannot find again) the VREF was connected to an MCU pin.

If I do not use the reference, can I safely presume I can leave it floating?
35  Using Arduino / Microcontrollers / Re: Uno R3 USB / serial reset on: October 30, 2013, 03:09:38 pm
Hi all...

Quote
Is it possible to remove the cap and the diode in the reset circuit, I don't see why it needs to be there? If a chip like an FTDI230X can just pull the line low, surely a reset occurs?

It seems that may have been worded wrong, and that people may be misinterpreting it... it was in no way a dig at the team that designed the boards at all, but rather my way of simply asking how it really works, after all - that's how I learn.

Quote
You would do well to simply copy what you see and are told to do, when you ask for advice. Then IF it doesn't work ask why...

Do you really mean that, if it dosen't go wrong - so you don't ask how it works, how to you know to apply it elsewhere if you don't understand how it works?

Anyway, thanks for the replies - they have indeed helped.  smiley
36  Using Arduino / Microcontrollers / Re: Uno R3 USB / serial reset on: October 30, 2013, 05:10:04 am
Thanks for the replies, one thing I'm unsure about however.

The 8/16U2 is waiting for a certain signal over USB (what is this signal, opening and closing of the serial port?), to pull the main MCUs reset pin low with a virtual DTR pin?. However, how does the host know that the cable has been connected to send out the DTR signal anyway?

As in, I know how avrdude sends a command to the 16U2 which resets the main MCU, but why does it reset when you open a serial monitor?

EDIT - I think i've just answered my own question whilst typing this - I haven't got a board with me at the moment, but I think I've been stupid... the board dosen't reset when you connect a cable, but when you open a serial monitor in the Arduino IDE?

Quote
It's nothing to do with the bootloader. The 8U2 responds to the DTR signal and brings DTR low, which becomes a pulse because of the capacitor (C5 on my schematic) in series.

Why the series cap though? Programmers like the ISP Mk2 don't need that cap in series?

Is it possible to remove the cap and the diode in the reset circuit, I don't see why it needs to be there? If a chip like an FTDI230X can just pull the line low, surely a reset occurs?
37  Using Arduino / Microcontrollers / Re: ATtiny 1634 support? on: October 30, 2013, 04:35:43 am
Sorry to pull up an old thread, the forum is warning me not to - but I don't see the point in a new thread here.

I too am looking to be able to program the attiny1634 using the Arduino IDE, can anybody point me in the right direction to be able to do this?

What sort of files will I need to make?

Quote
There's been a lot of answers saying it looks just like a Mega328.

If that's true you just need to edit your "boards.txt" file and add a new entry.

What do you mean when you say, 'looks' like a 328?
38  Using Arduino / Microcontrollers / Re: Arduino newbie - do sketches stay in the board during power down? on: October 29, 2013, 05:24:35 pm
Just for the future... if you use the internal EEPROM memory to store data, then you will lose whatever data you stored in there, as it is volatile memory.[/s]

EDIT - You won't lose EEPROM data either...  smiley-kiss But still, it can only be used a finite number of times, and tricks in software can help with not writing unless absolutely necessary, and spreading out the wear on the cells.

You can also only use it finite amount of times before it fails.
39  Using Arduino / Microcontrollers / Re: Uno R3 USB / serial reset on: October 29, 2013, 02:55:02 pm
Yes I had a good look at the schematic and saw the connection - I presume this is done then in the bootloader like with the Due, where opening and closing of the port triggers a reset.

Cheers!
40  Using Arduino / General Electronics / Re: Using Microchip MCP2200 instead of FTDI FT232 on: October 29, 2013, 10:08:59 am
Macegr, you make a very good point - if for some reason you're application needs to send the datastream that would toggle the GPIO, you're stuffed.
41  Using Arduino / Microcontrollers / Uno R3 USB / serial reset on: October 29, 2013, 09:40:24 am
Hi all,

Just to clarify something here... unlike the old Uno and Duemilanove - as the Uno R3 dosen't use an FTDI chip, how does it perform the reset when you open a serial port from a USB host?

Is it the 16U2 pulling the reset pin line when it recognises there's a USB host connected? It must be...
42  Using Arduino / General Electronics / Re: Yellow from an RGB LED, but not from ink mixing for example? on: October 24, 2013, 08:13:31 am
Ah, i'll have having a good read of that later - something I've never really thought about until now...

Thanks!
So you would rather wait to be spoon fed than find out an answer as it involves you in a bit of work.?

Yes.... that or I was working on something else that needed my attention, such as work, and would read the wiki pages later that day.

Anyway, to all those who replied with constructive comments - many thanks. The LEDs I'm using are highly diffused, as I have seen reference to issues with PWM and true colour mixing before.
43  Using Arduino / General Electronics / Re: Yellow from an RGB LED, but not from ink mixing for example? on: October 23, 2013, 05:46:08 am
Ah, i'll have having a good read of that later - something I've never really thought about until now...

Thanks!
44  Using Arduino / General Electronics / Yellow from an RGB LED, but not from ink mixing for example? on: October 23, 2013, 04:46:04 am
Morning,

I've just had a thought - I'm using an RG LED in an application, as in - Red and Green, no blue. Looking around at sources like this - http://uk.farnell.com/rgb-led-lighting-applications shows quite clearly that turning on both red and green at the same time gives yellow.

However, if you mixed red and green paints - you'd just get a dirty brown, not a nice yellow? Why this is?

I guess it's because you're combining two different wavelengths together or? hmm...

Thanks!
45  Using Arduino / Microcontrollers / UART interference with USI port acting as I2C master on attiny1634 on: October 22, 2013, 08:35:28 am
Hi all,

The title sort of says it all - I'm using an attiny1634 MCU, and have got a 6 pin ICSP header connected so that I can program the chip using SPI. However, I'm also using the USART that's on the same pins as SPI - to communicate with a FTDI USB - UART converter. The ICSP header is connected directly to these pins, and the USB - UART connected through 10K resistors - so there shouldn't be any sort of electrical interference when programming the chip over SPI.

Also, USB will never be connected whilst programming with the SPI port anyway, so that chip shouldn't be driving its pins. (do I need to check if the converter goes into high impedance here when disconnected, or does the fact I've got 10K series R make the programmer see the chip as high impedance anyway?)

However, I also want to use the USI interface (universal serial interface, that can act as a I2C master amongst other things) which is of course located on the same pins as said USART, to communicate with a FRAM memory over I2C.

The USB - UART converter will never be connected to a USB host whilst the I2C bus is active, as there is no way a user could plug in a USB cable during the condition that would cause a write to the FRAM device, as they cannot physically get to the device during operation.

So, my main question is - will the pull ups required by the I2C SDA line interfere with the UARTs RX communication from the USB converter?, when the I2C mode is inactive, and the normal UART mode is active?

(that leads me on to another question, I wonder if the UART mode can be deactivated, and the USI mode activated during code execution, and not as a start up setup)

Many thanks in advance!
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