All Questions

Filter by
Sorted by
Tagged with
7
votes
3answers
2k views

Where to find pre-made wires for plugging into headers? [closed]

Headers like these: http://uk.farnell.com/harwin/m20-8760342/header-smt-vertical-2x3way/dp/1517388 I'm looking for cables that connect to these, with female headers on either end. Any length more ...
17
votes
4answers
16k views

How critical are UART frequencies?

I'm going to be using an 8 MHz crystal to run my microcontroller at 16 MIPS (PLL 4x, 2 cycle instructions.) However, 8 MHz doesn't divide into any UART frequencies AFAIK... so how critical are these ...
5
votes
2answers
784 views

Can anyone identify this phone PCB?

Can anyone identify this mobile phone? http://www.adafruit.com/blog/2010/10/29/what-is-that-electronic-thing-from-yemen/ http://www.flickr.com/photos/ladyada/5126516011/ http://www.bunniestudios....
7
votes
5answers
5k views

Is Y5V okay for decoupling capacitors?

Y5V capacitors are much more temperature dependent, but is that really critical for decoupling capacitors and a product operating over a -40°C to +85°C range maximum (typical -20°C to +55°C)? The ...
1
vote
3answers
472 views

ipod headphone jack only driving one side - is there an easy way to fix this?

The headphones work fine in other devices. If I push or pull the connector a little bit I can get sound from both. It is apparently an issue in the mechanical connection of the jack. Has anyone had ...
3
votes
2answers
352 views

Is there a good and reasonably priced way to make a custom RFID reader and barcode scanner that runs Android?

I'm building a system for a small manufacturing business that requires a mobile barcode scanner (at minimum) and would be great if it could be an RFID reader too. I would really like this to be a ...
3
votes
3answers
587 views

General tips for 4 layer boards

For my Super OSD Pro project (Super OSD is divided into two versions: Lite and Pro) I'm going to be using a 4-layer board. Are there any gotchas to be aware of when using 4 layer boards? I was ...
36
votes
5answers
10k views

Are decoupling capacitors needed with battery power?

Currently I run all my gadgets from batteries and don't use decoupling capacitors. Are they generally needed/useful when drawing energy from a battery?
1
vote
1answer
2k views

Difference between CD4017 and CD4017B

I have a choice between a CD4017 and a CD4017B. I've also seen CD4026 and CD4026B. What is the difference between these - is it a silicon revision or do they have different functionality?
7
votes
4answers
42k views

What is the difference between PLA and ROM?

I'm finding it hard to understand. What is the difference between PLA and ROM? Can somebody please provide a link or explanation?
2
votes
3answers
735 views

Reading up to 8 PWM's

I want to read 8 PWM inputs (standard servo PWM, 1ms to 2ms) without an input capture module (my module only has 7 channels.) Could I use a capacitor and the ADC on my MCU? Does anyone know of any ...
1
vote
6answers
597 views

Looking for a small inductor buck converter in a SOIC-8 package [closed]

I'm looking for a buck converter in a SOIC-8 package which requires a small inductor (preferably ≤10µH) which can convert 6V-16V to 5V @ 1A. Unfortunately the package must be a SOIC package, because ...
2
votes
1answer
206 views

Remote pan a 2.7m carbon fibre camera pole

I am building a pole camera, normally you would have someone on the other end to move the pole, but we want to be able to operate it remotely. As the movement needs to be very smooth, with a soft ...
2
votes
8answers
2k views

How to poll UART while processing lots of other stuff

I have a GPS device which I need to pull data from (the NMEA strings.) However, many times per second my MCU will be busy processing something else. Is there any way to "pause" an UART/RS232 TTL ...
0
votes
3answers
1k views

Comparator over I2C with programmable reference

I'm looking for a programmable comparator which has a digital or open-drain output and a voltage reference which can be programmed over I2C. My searches at my favourite sites of Microchip and Farnell ...
12
votes
3answers
7k views

How do 'hand clap' switches work?

I'd like to know how a 'hand clap' switch works. You know, the kind where you *clap-clap* and the light turns on, *clap-clap* again and the light turns off. How is the clapping sound detected? How ...
2
votes
5answers
1k views

Microcontroller with >30KB RAM and high performance in a TQFP-44 or similar package

I'm looking for a microcontroller in a TQFP-44 package with 30 KB or more of RAM and, if possible 40 MIPS instruction cycle speed or faster. I can find dsPIC33F's with 30 KB of RAM, but they come in ...
11
votes
3answers
2k views

Decoupling capacitors

Many IC's I've seen suggest decoupling capacitors across Vdd to Vss - this is sensible. However some IC's for example the dsPIC33FJ128GP802 has THREE Vss pins and only two Vdd pins (AVdd and Vdd.) So ...
4
votes
2answers
714 views

How to interface a Blackberry Torch with a serial device?

I have a Blackberry Torch that needs to send 10 bytes per second to a serial device. The serial device will probably be a basic stamp 2 or other microcontroller. The Blackberry does not need to ...
5
votes
1answer
2k views

Characteristic impedance of a trace

I'm trying design a video transmitter around an 5.8GHz Airwave module. The documentation says the trace to the antenna must have a characteristic impedance of 50 ohms. How do I calculate the ...
6
votes
4answers
1k views

How are dot matrix LCDs controlled?

I've seen microcontrollers which claim to drive LCD segments. For example, the CC430 can drive 96 segments. But, it's a 64 pin chip. So, it must be providing signals for some kind of mux, what is ...
7
votes
1answer
748 views

Helical antennas and orientation

A batch of questions here really (if it helps I'm operating at 433.92MHz): How should I orient a helical antenna with respect to my board (i.e. my "ground plane") to get the best range performance? ...
17
votes
11answers
29k views

Should I buy a Netduino or Arduino?

I am looking at buying a NetDuino for some fun home hobby projects. Have any of you used it and how was your experience? Should i look at the Arduino or FreeDuino range instead(or something totally ...
7
votes
3answers
1k views

Connecting two phone handsets to talk

I am hacking some old phones into my arduino project. I am currently controlling all of the ringers, dials, and hooks through my board. At a certain point, I would like to connect the two handsets ...
14
votes
2answers
7k views

Is it normal for DC wall adapter power supplies to provide voltages above the nominal ones?

When I measure a 9V DC wall adapter power supply with a multimeter it shows 11.8V. When connected to my board this voltage lowers to 10V. Is this normal? Should I be afraid of toasting my 1117CD-5.0 ...
2
votes
1answer
7k views

How to send data through XBee using ATMega328?

I bought Seeeduino Stalker UartsBee Two XBees When I physically connect (1), (2) and the computer USB, I can receive on my computer data sent by (1) at 115200 Kbps. But when I physically disconnect ...
4
votes
6answers
3k views

What's causing this high frequency ripple on the output of my LM317?

I'm using an LM317T to regulate 5 V to 3.38 V for a microcontroller. R1 is 330 ohms and R2 is 560 ohms. There isn't any input capacitor and the output capacitor is 470 µF 25V, because I ...
5
votes
6answers
6k views

Why do my compact fluorescent lamps keep dying?

I know that this question may be off-topic here, but I'll ask it anyway since they do have electronics inside. I've noticed that my fluorescent lamps keep dying after only couple of months of use. ...
8
votes
4answers
1k views

What is needed to go from single Ethernet to many?

I have an embedded Linux system with a single Ethernet port, but I need to go to many ports. It is obvious I need to add magnetics and ports. The trickier parts follow. My processor has an on-board ...
5
votes
2answers
247 views

What a weird operating range, 2.97V to 3.63V

I've seen several microcontrollers rated to operate from 2.97V to 3.63V. Others I've seen rated from 3V to 3.6V. What's with the extra 30mV on either end of the scale? It doesn't seem like it would ...
19
votes
3answers
5k views

Getting started with PCB Layout for BGA Packages

Are there any good resources for learning the intricacies of PCB layout when dealing with BGA packages? I'm very familiar with layout for almost every SMT part that has leads on the edge (QFP, TSSOP, ...
4
votes
2answers
2k views

Create a robot arm using microcontroller

I am planning to create a robot arm using the MicroController. The robot arm should move from the angle of 0 degrees to 60 degrees. I am going to use this robot arm in my application to stop and ...
8
votes
9answers
3k views

Serial control of 25 LEDs from a single pin

I have a microcontroller with one available digital pin. How can I control 25 LEDs?
3
votes
5answers
7k views

How to compare two audio files?

I have two recorded audio voice WAV files I have recorded by saying "Good Morning" twice. I want to compare the two audio files and say both are identical. How can I do that? What is the right ...
9
votes
2answers
1k views

All Digital Phase Lock Loop

I'm looking to implement a phase lock in an FPGA without using any external components (other than the ADC). For simplicity locking to a simple binary pulse is adequate. The frequency of the signals ...
0
votes
2answers
660 views

Balance board with Arduino

We're trying to build a rudimentary Balance Board using four force sensitive resistors and an Arduino unit, but are not sure how to wire up the circuit. How do we connect the sensors to the Arduino?
7
votes
4answers
8k views

Tolerance of voltage dividers with different values for R1 and R2

If I have two 1k resistors rated at 1% fed by a perfect 10V source then what is the otuput guaranteed to be? 5V ±1% or 5V ±2% or some other value? I can work out this case easily, assume that R1 is ...
1
vote
1answer
375 views

Microcontroller board with ethernet for computer sensors

I'm considering the possibility of using an ethernet-connected (SNMP would be a bonus) microcontroller board of some sort to monitor a RAID card inside a server that doesn't have OS support; the card ...
5
votes
4answers
2k views

Increasing ADC resolution by supersampling on a successive approximation ADC

Is it possible to increase the resolution of an ADC by supersampling on a PIC24F ADC, which has 10 bits of resolution and is implemented using a successive approximation engine? Speed is not critical -...
21
votes
3answers
937 views

Microcontroller with both ethernet and radio onboard?

Does anyone know of any (reasonably low-cost) SoC which combines all of: Microcontroller (any architecture, at least 4KB RAM/8KB flash) Radio transceiver (433MHz - 915MHz or 2.4GHz) Ethernet MAC + ...
12
votes
5answers
2k views

Minimalist Cortex-A9 design

Does anyone know of a good basic Cortex-A9 design? Something with just enough to run with power and ethernet? I'm looking for something as a starting point and maybe with eagle files. edit: While ...
1
vote
3answers
507 views

High voltage/Mid current boost converter

I'm designing a regulator/converter that can generate -120/-108/+60Vdc for a current of 180mA each from a supply of 12Vdc or 24Vdc (5A like it's nothing, 15A tops) and I was choosing a MC34063 but the ...
6
votes
3answers
5k views

How do these powerline networking adapters work?

I have some powerline networking adapters which can transfer at a peak rate of 200 Mbps (I get around 60 Mbps typical, but I am sharing the network with many other devices and many pieces of equipment ...
14
votes
9answers
12k views

Is it worth getting a function generator?

Is a function generator necessary for every day lab use, or is it special purpose equipment? That is, does it have similar utility to an oscilloscope, or multimeter - would you use it regularly enough ...
2
votes
1answer
10k views

Damage to diodes by exceeding Vrrm

How is a diode damaged by exceeding its Vrrm (maximum peak repetitive reverse voltage)? At this point it conducts more current than usual, so is it the current flow that damages it? Why would that be ...
27
votes
3answers
16k views

Are coin cells a suitable replacement for AA batteries?

I am currently using AA batteries in my projects but would like to look at cell batteries for my next project, due to their compactness. Apart from the physical appearance, how do cell batteries ...
3
votes
2answers
921 views

Hot ENC28J60 @ 132 mW

I have a problem with a relatively simple board which consists of an ENC28J60 Ethernet controller and an ATmega168. The circuit around the ENC28J60 is straight out of the datasheet and I have the ...
5
votes
2answers
2k views

Why the difference between maximum junction temp (150°C) and storage temp (165°C)?

Many integrated circuits I have seen have the specification of maximum junction temperature (150°C) but storage temperature is invariably higher (165°C) and often lower, e.g. -55°C. Why the ...
10
votes
6answers
15k views

Can a credit card be demagnetized with a nearby cellphone?

Suppose I have a standard credit card with a magnetic stripe, lying right on top of a cellphone, or in a regular leather wallet that's lying right on top of a cellphone. The cellphone is on (but ...
2
votes
1answer
1k views

Increasing the delay using 'option' register in Pic16f877a

I have learned that the maximum 'delay' possible in pic16f877a running with a source of 11.0592MHz (11059200 / 4 actually) is 23 ms.. without using software delays (delay_ms( )).. the calculation was ...

15 30 50 per page