Tagged Questions

All related to methods to select the correct components and/or component values to specific applications

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0
votes
1answer
30 views

Size of passives for active filter

I am working with the CS42436 codec, and in their datasheet, they have recommended values for components to be used in an active filter that takes the differential outputs from the DACs and converts ...
0
votes
2answers
35 views

Component selections for the ETA3406 DC/DC converter

I was browsing Seeed Studio's Open Parts Library and found the ETA3406, which is a 1.5 MHz 1.2 A Step-Down Converter. It's pretty cheap, and looks very useful for something I want to build, but the ...
4
votes
2answers
125 views

Inductor selection for obtaining a noiseless analog power rail

I interface an image sensor, and the design schematic for power supply is: How do I choose one from the available 3uH inductors based on the specs? I figured the maximum current and dc resistance ...
1
vote
1answer
31 views

Selecting continuous pull type solenoid

I own a Rail track master and it needs two pull type continuous solenoids. The age of this machine is from the 1950's and both of the previous solenoids were unidentifiable. These solenoids operate ...
0
votes
2answers
56 views

What are the selection parameters for an NPN BJT?

I'm building an NPN-based driver circuit for disconnecting my battery level measuring voltage divider when not in use. Here's the circuit: ...
8
votes
1answer
168 views

Antenna matching network topology

In tuning an antenna, there are multiple possible topologies that will take it to the middle of the smith chart. Some differences that I can see between them are: Component ESR (losses). Effect ...
0
votes
3answers
79 views

Finding a replacement voltage regulator… what do the codes mean?

So I need to replace the following voltage regulator in an old Atari as it's registering 0.5V between output and ground and 24V on the input, but it's supposed to be providing 12V on the output side ...
0
votes
2answers
91 views

How do you choose a diode for a 5v to 3.3v clamping circuit

I have a logic input that is 3.3v and I want to be able to allow it to interface with either 3.3v or 5v input signals w/o worrying about it being damaged. I would like to use a resistor with a ...
1
vote
0answers
27 views

Can I change a design from using one polypropylene cap to four PEN/PET caps in series?

I've inherited a design for a SEPIC converter that uses a polypropylene input filter capacitor from CDE. (Specific part number 715P472516LD3.) I'm considering shifting this design to surface-mount ...
2
votes
1answer
136 views

Choosing capacitors for Microwave RF application

I've recently been given a project to lay out some PCBs which will contain a few Mini-Circuits RF amplifiers, and their associated biasing components. However, since I need to have several stages of ...
5
votes
5answers
250 views

Which parameters in datasheet give information about a BJT's step response quality?

I did a test with randomly chosen 12 NPN BJTs. I applied a clock pulse to each of them and observed their collector voltages. Some of them showed very low rise time, while some responded terribly ...
0
votes
0answers
69 views

Best possible specs for a MEMS mic in 2014?

I want to use the best MEMS mic that's on the market today (June 2014) in terms of audio quality. Since I know that "shopping" questions are forbidden, I'll phrase it like this: What are considered ...
4
votes
2answers
646 views

How to tell if an electronic component is counterfeit?

I've been looking into sites (like Alibaba, etc...) for components, but they are usually at the price of the rain. How can someone know if a company or factory is not a scam and that those components ...
1
vote
1answer
85 views

How to find SMT equivalents of TH parts?

A lot of times hobbyist circuits are designed with thru-hole components since they're easier to solder. What approach do you take when attempting to find the SMT equivalent of a TH part? For example, ...
0
votes
2answers
51 views

Does DC-powered polarizing film exist?

Does anyone know if there is a component or a solution for creating a switchable polarizing film using DC-power? (i.e. a film/glass/substrate/etc that can be switched between a polarizing and a ...
0
votes
0answers
95 views

Mini PCIe switch with 1 lane 2 devices?

I have a doubt, I have a SoC with 1 lane of PCIeV2 and I want to connect 2 wifi modules through PCIe to the SoC, so I want to use a PCIe switch to do it (the 802.11n is 600 Mbit/s and the PCIeV2 is ...
0
votes
0answers
176 views

Finding/figuring out pin configuration on undocumented components

I recently purchased an assorted set of LCD/LED displays, and inside there were a set of components which I cannot find a datasheet for upon googling the component number. For instance in the ...
7
votes
1answer
225 views

Help me modernize this audio circuit

When I was a kid, I built this circuit. You hook up a small capacitor to the test leads or maybe a couple in parallel and the speaker will output a different pitch based on the test capacitance. I ...
1
vote
2answers
114 views

How can I maintain a fix voltage until my battery is almost dead?

I am experimenting with a simple circuit. I have an Arduino board, a proto-board and an IR sensor (that uses electricity from the Arduino board). I use a 9V battery to feed the Arduino. My problem ...
1
vote
1answer
113 views

Rectifier component for PCB

I'm looking to change my breadboard design of an amplifier into a PCB. This is the first PCB I've designed and I'm not sure what sort of components to get. My original full wave rectifier is made ...
1
vote
1answer
79 views

How do I find a matching plug & header pair?

I'm browsing board to wire type connectors. My aim is to solder a header on my PCB, and use a plug to receive/transmit signals from it. As far as I see, the headers and plugs are sold separately, and ...
0
votes
0answers
41 views

How to chose a compatible, drop-in replacement for a TSOPII-54 SDRAM module with more space?

I have a device that uses a PSC (Powerchip) A2V64S40CTP-G7 TSOPII-54 SDRAM chip. It's a 64MBit (8MB) RAM module. I'd like to put a larger chip in that device, and what I need to wrap my head around, ...
5
votes
2answers
1k views

How to Calculate Complex Low Pass Passive RLC Filters?

I have designed a FPGA based DDS and now I want to add a low pass filter to its output. Previously I was working on a project based on AD9850 DDS(0-50MHz) and I had a commercial module for it that had ...
9
votes
5answers
579 views

Sensor for ultralow (to -85°C) freezer monitor

I am planning to build a series of Arduino-controlled temperature-reporting units for a room full of "Ultracold" -80°C freezers. (I ultimately want to convert the signal to a serial stream that will ...
2
votes
2answers
254 views

Component for covering a very tiny hole (pinhole camera aperture)

I am experimenting with a pinhole camera - it is basically a camera with a very small hole (only 0,2 mm in diameter) instead of a lens (Wikipedia) I am trying to design the shutter - something that I ...
2
votes
1answer
133 views

What must be rated maximum voltage of the boot-strap capacitor of a high-side MOSFET driver?

What is the maximum voltage that appears on a boot-strap capacitor? For example, in this circuit, does \$C_B\$ ever charge to a voltage level near \$600V \pm V_{cc}\$ ? Or does it charge to ...
0
votes
1answer
289 views

IC to interface between digital switches (12V) and microprocessors (3.3V)

I am working on an automotive general purpose ECU where I need to interface 12V digital inputs with a µC (3.3V). The PCB space is limited, so I am searching for a single IC as an interface between ...
1
vote
1answer
139 views

What kind of capacitor should I use in Buck topology if the load is a lead-acid battery?

I'm using BQ2031 to charge lead-acid batteries. BQ2031 takes battery voltage as feed back and controls the switching element according to it. Now the load is not a passive element, instead it is a ...
4
votes
3answers
3k views

What is the difference between 1N4001 and 1N4007 other than their maximum reverse voltage?

I compared 1N400x diodes here. As far as I see, all of their properties are same other than their maximum reverse voltages. Their maximum current recovery time reverse leakage current capacitance ...
2
votes
1answer
187 views

Micro switch that closes circuit twice, on press and on release

I need to implement a switch that closes a circuit twice for a short time - when pressed and then when released. The switch needs to be really small (should fit inside a 3.5mm TRRS headphone jack, ...
8
votes
5answers
286 views

Selecting a MOSFET for DC use

I have a general question regarding MOSFET Selection. I am trying to select a MOSFET for DC use. I am looking to replace a 5A 24V Relay with a N Type MOSFET. The MOSFET would be driven from a micro ...
3
votes
1answer
964 views

Selecting capacitor for voltage-divider of half-bridge high power SMPS

How to dimension the capacitor for the voltage-divider of a half-bridge high power (>5KW) SMPS power supply? The question is more on type of capacitor and current rating than the capacitance. I have ...
2
votes
2answers
176 views

What do I need to look out for when converting 9V example schematics to 12V?

What do I need to look out for when converting 9V example schematics to 12V? Most of my ICs work until 18V, and it seems to me all the resistor divider stuff is based on ratios, so it should scale ...
19
votes
5answers
669 views

How to ensure long-duration manufacturing of central components?

This question is related to project planning and minimizing risks in the future. Say that Company X builds this clever device (I do not own a company - I am just curious). The clever device takes ...
0
votes
2answers
199 views

Disadvantages of building own components (such as SR latch)?

So I browsed Digikey for way too long today looking for an SR latch. I wanted something low power that would use very low quiescent current for a varied range of VCC and work for between 2-5 volts ...
1
vote
2answers
351 views

Will the B constant for 10k ohm NTC thermistors be the same from all vendors?

I recently purchased a 10k ohm NTC thermistor from a local electronics store for which I couldn't find a datasheet. By going through the post How to measure temperature using a NTC thermistor I ...
1
vote
2answers
235 views

Varistor S10K30 for 24-40VDC input?

I was put in charge of redesigning a motor control circuit which accepts 24-40V DC on its input. As a side note: As far as i know, the existing circuit has been working fine for several years. The ...
0
votes
1answer
618 views

Will a capacitor of 10uf 250v work as good as a cap 10uf 50v?

what is the difference between electrolytic capacitors 10uf 250v and 10uf 50v? if i connect it to my circuit with a 9v battery? will the 250v cap work? or which is the most preferred for a 9v ...
6
votes
2answers
2k views

What is the “ammo” packaging method when ordering through hole parts?

I'm familiar with bulk, tape and reel, cut tape, and tube, but what is "AMMO?" Source: Fairchild 2N3904 datasheet, page 2
7
votes
4answers
259 views

Resistor selection for LED

This isn't asking the equation to determine the necessary resistor for LEDs, but more asking the general practice for selecting them. I've seen multiple circuits that have used much higher resistor ...
1
vote
2answers
363 views

Cannot find efficient current/voltage regulator to power LEDs

I have a 12V 4-pin common-anode RGB PWM'd signal being used to power some LED strips, and I would like to use it to power the VL-H01RGB00302 Vollong 3W RGB High Power LED - which is basically a set of ...
3
votes
4answers
1k views

Widely available IC for encording and Decoding DTMF data

I am planning to do some research in data transmission over the air. For this I am interested in DTMF encoding and decoding. Is there a widely available IC to achieve this? A circuit diagram using ...
4
votes
2answers
205 views

How do proceed with larger electronic projects?

Recently I have read two books about programming in general: First one being Code Complete and the other being The Pragmatic Programmer that describe how one should think when dealing with large ...
0
votes
2answers
153 views

Source for a 6-pin DIL “stackable” header (for Arduino ICSP header)?

Does anyone know of a source for a "stackable" 6-pin DIL header? I would like to use one on an Arduino shield I am designing, in order to carry the ICSP header from the Arduino up through the shield ...
1
vote
2answers
178 views

USB device with a serial number and 3 LEDs

I'm looking for a way to build a USB key. I have a bit of experience with the Arduino, however for this project that seems to be a bit of overkill. The key should contain a unique serial number ...
70
votes
5answers
5k views

What is the reason that the value “47” is so popular in electrical engineering?

We often see component values of 4.7K Ohm, 470uF, or 0.47uH. For example, digikey has millions of 4.7uF ceramic capacitors, and not a single 4.8uF or 4.6uF and only 1 listed for 4.5uF (specialty ...
1
vote
1answer
341 views

Help identifying/selecting SMD MOSFET

I am repairing an IP camera that has a blown transistor in the power supply section. The transistor looks like a SOT23 transistor, but it has 6 pins (how is that package called, anyway?), 4 of them ...
1
vote
1answer
280 views

What there was before Arduino? [closed]

I'm really a fun of Arduino project, it's easy and it has a great community. But i am aware that is has no technological innovation, it is only a wrapper on a (normal?) microchip, if i have understand ...
-1
votes
1answer
184 views

Help finding Buck/Boost Regulator IC [closed]

I have been trying to find a suitable Buck/Boost IC with certain features, but having gone through multiple Manufacturer's product tables, I can't find one that meets my needs. I think this is more ...
23
votes
1answer
625 views

Darlingtons, MOSFETS, and bipolar junctions

I realize there are dozens upon dozens of kinds of transistors, each used for specific purposes. Sometimes there is great overlap; multiple kinds may work in a given circuit, but at times only a ...