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0
votes
2answers
31 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
47 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
43 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
210 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
82 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
97 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
55 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
30 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
606 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 ...
8
votes
5answers
361 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
142 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
96 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
170 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
99 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
953 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
161 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
228 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
564 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
155 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
652 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
131 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
205 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
126 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
349 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
743 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
221 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
258 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
750 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
195 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
1answer
94 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
153 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 ...
63
votes
4answers
4k 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
271 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
243 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 ...
0
votes
1answer
135 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 ...
22
votes
1answer
572 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 ...
-6
votes
1answer
286 views

Information required in building DIY HHO production device [closed]

I am going to try producing HHO (creating hydrogen and oxygen) and have been told that a "100 Amp 12 volt pulsed wave modulator" will increase the HHO production. I believe they mean pulse width ...
4
votes
2answers
436 views

For switching 220VAC, is a specific coil voltage and coil resistance better than another?

Is there any reason why I might choose an EM-relay rated at coil-voltage of 24V or 12V, over one rated at coil-voltage of 5V, all other specs like contact max. current, switching voltage, life etc ...
3
votes
3answers
154 views

Choosing an MCU in a time-effective way [closed]

I'm spending a lot time figuring out which microcontroller I should choose for my projects. For example, for one project I have the following requirements, in order of importance: I2S interface ...
2
votes
4answers
476 views

Infrared spotlight project, need x50 resistors. How many ohms what type to use?

Infrared spotlight project. I have a PCB BOARD set up for 150x 5mm IR LED 1.5-1.6 forward voltage. Forward current is 60 mA 150 LED’s are divided into 50 groups (3 LEDs each + 1 resistor) What ...
7
votes
1answer
414 views

Using the VO2223A to switch a 230Vac LED lamp

I'm looking for something that can switch on and off a 230 Vac, 26mA LED lamp, under microcontroller control. Would a VO2223A, driven by (say) a PIC or Arduino, work as a low-current SSR? The load ...
1
vote
2answers
275 views

How to select a proper transistor?

I've got a schematic that calls for an unspecified "NPN Negistor". From my understanding of the circuit, the NPN is an oscillator that generates two audio tones for testing. Here's the schematic: ...
0
votes
0answers
178 views

Sound level meter for a given range of frequencies

I would like to measure the quantity of noise. For example, I have found this sensor: http://www.phidgets.com/docs/1133_User_Guide ...
7
votes
2answers
311 views

How do you work out ripple current for a Power supply design

I hear the ripple current rating of a cap is important because caps have internal resistence which can cause over heating of capacitors. I was wondering is there any general rules a professional ...
1
vote
2answers
1k views

How much voltage/amperage can a NPN transistor take?

I got the MakerShed Ultimate Microcontroller Pack and it came with a "Transistor NPN". I want to use it (or probably buy something else) as an electronically controlled switch so that on arduino I set ...
1
vote
2answers
199 views

Flush/slotted actuated rotary switch knob?

I'm thinking of using the R10015RS02Q SP10T rotary switch for an upcoming project I'm working on. It's marketed as having a flush/slotted type actuator which I think requires something like a ...
4
votes
1answer
454 views

What kind of knob fits a slotted potentiometer shaft?

What I thought was an easy question is more elusive than I suspected. I have a number of potentiometers that have smooth (not knurled) shafts with a slot cut into the end...it looks like a flathead ...
3
votes
2answers
725 views

Ideal analog switch to replace BJT / MOSFET in the modern world

When tackling with the very common need of toggling a current with an output from a microcontroller or similar chip, solutions have varied over time. The oldest solution is to just use a BJT. This ...
4
votes
2answers
1k views

What's the difference between linear and audio tapers, and why should I care?

I'm stocking up on a variety of potentiometers to keep on hand for my audio projects, and I'm trying to figure out what to buy. The projects I'm working on seen to call for either linear & audio ...
3
votes
1answer
268 views

rotary switch / turn knob? how to call it?

Im looking for a switch-like rotary knob, that i can turn left and right. Its outputs a simple 'pulse'. You find these in selecting/setting numbers on assorted electronics. You can keep turning them ...