Question 1

Sound card problem

Accepted Answer

I want to process the signals of five electret condenser microphones with raspberry pi and i since the RPI has no audio inputs im thinking of using a sound card. Im looking for a sound card with five simultanious inputs in order to do synchronized sampling, im thinking of using the Wolfson Raspberry Pi Soundcard, is it capable of achieving what i intend to do? If the wolfson sound card is not capable of that, is it possible to do that with the MCP3008 ADC?   Electret mic:  MCP3008:  Best regards, Tareq Matar

Question 2

Driving LEDs with constant voltage

Accepted Answer

I have some 7-segment displays I'd like to drive from a uP output...the  segments have a common cathode. 5 volt digital outputs from the uP are available, and the red LED  segments have a forward voltage of around 2.something volts.  Current-limiting resistor networks are annoying..so I was thinking of  just connecting the display cathodes to one output per digit through a  TL431 with its REF and anode connected to give 2.5, basically using it  as a zener to drop the voltage, and switch those outputs to scan the  multiplexed digits.

Question 3

Rectangular LEDS

Accepted Answer

I'm thinking of making a Set Theory Clock display for a desk clock and  using LEDs for its display. This needs a selection of rectangular red and  yellow LEDs, both small stackable ones that could be used to make a VU  meter type bar display: 1.5x5mm or (preferably) 3x10mm tops ideal and  some bigger ones: 5x5mm or (preferably)10x10mm tops. I've just been looking at online catalogues. Maplins and Farnells don't  appear to have anything except round LEDs while RS don't have anything  bigger than 1.5x5mm rectangulars and nobody appears to have them in  yellow. I remember that these types of LED housings used to be around, so can  anybody suggest where I may be able to get them now? --  martin@   | Martin Gregorie gregorie. | Essex, UK org       |

Question 4

Controlling alot of LEDs from Arduino or AVR.  Maybe 74HC595

Accepted Answer

I am trying to create a project much like like a Marquee sign,   I want  to be able to control hundreds of LEDs from a set of chips.  From my research I found the 74HC595 chip and using a bunch of these would probably work, but it would be nice if I had the ability to change each intensity of each LED like each LED pin had its own PWM controller on each LED ?Is there a chip-set out there that would do some thing like that ?ThanksSid.

Question 5

wart  overvoltage protection

Accepted Answer

We make a gadget that's powered by a 12 volt wart, and sometimes auser applies 24 and blows one up.We have a polyfuse and a 12 volt TVS and they sometimes fry the TVS.It's posssible that most any useful polyfuse+TVS combo can be teasedto destruction.I think Phil H mentioned some gadget, a polyzorb or something, thatwould be better. I can't find it.We might fine-tune the polyfuse+TVS, or maybe go polyfuse and SCRcrowbar, or something.This is all entangled with parts availabity. Ideally the box wouldjust work from 12 or 24, but that has separate complications.We once used a TI electronic fuse IC, but it liked to blow up.

Question 6

Radio Reception - Massive Electrical Interference

Accepted Answer

Hi!I just moved to an apartment and wanted to keep my radio in the bathroom, same as I did in the last place I lived.Only problem with this place is that the main electrical drop to the building is right outside my bathroom wall, interfering with FM/AM reception.Is there anything I can do to alleviate this - putting a noise filter on the radio power cord, etc??Right at the frequency of an AM I've been listening to for years, is a loud combination buzz/screeching sound.

Question 7

atiny13 to atiny25

Accepted Answer

I'm in the process of shfiting a board using Atmel's atiny13 to the atiny25. The at25 is causing lots of trouble.    First hassle was getting the at25 to accept the "program enable" command. There was no response. The data sheet states that an external clock signal is not required if the device is clocked by one of the internal oscillators. Presuming that the internal clock(s) was not connected, a 2mc signal was put on the clock input pin. Now the "program enable" command was accepted!   The "write fuse" command looks proper and the at25 returns the anticipated data but the "read fuse" command returns a 0 - not matching what was written.   The at25 appears to be fabricated by a different and newer process than the at13 which leaves lots of room for changes and errors.    Anyone familar with the at25, or other devices made on the newer process, have any suggestions for getting this working?Hul

Question 8

rec's for NiMH battery tester/charger?

Accepted Answer

I've got a big chunk of AA, AAA, and some C NiMh cellsof varying ages...I'd love to be able to get a reading of how muchcharge they're still able to hold...My info on this is decades out of date, so wonderingwhat suggestions people might have?Thanks_____________________________________________________Knowledge may be power, but communications is the key 		     [to foil spammers, my address has been double rot-13 encoded]

Question 9

Potting compound

Accepted Answer

Something optically clear, temperature range of -40C to +60C (70C would better)that can tolerate daily changes of ~30C for ~20 years.  Ideally, adherent to avariety of surfaces but I can compensate, if necessary.And, not exhorbitantly priced (I need gallons of it)

Frequently Asked Questions

Potting compound

rec's for NiMH battery tester/charger?

atiny13 to atiny25

wart overvoltage protection

Raspberry Pi Sound card problem electret condenser microphones

Radio Reception - Massive Electrical Interference

Rectangular LEDS

Driving LEDs with constant voltage

Controlling alot of LEDs from Arduino or AVR. Maybe 74HC595