Tagged Questions

DC stands for Direct Current, which means the flow of electric charge in a single direction. Examples of a DC source are batteries, solar panels, dynamos.

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0
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1answer
21 views

Amperage for Sony SNC-VB630 Camera [on hold]

I am trying to choose a right DC adapter for SNC-VB630 CCTV Camera but the only specs I could find in the official documentation was 'INPUT 12V DC'. Nothing about amperage. I have a 12V dc adapter ...
0
votes
0answers
35 views

PWM and brushed DC motor - AC input? Limiting RPM?

I'm looking to replace the 20-year old poorly-performing speed control in a MIG welder. It allows the user to adjust the speed of a small brushed DC motor, which drives thin welding wire of of a ...
0
votes
0answers
55 views

Calculate current in an series RC circuit with a DC square wave source?

Am still a noob in electronics so bare with me, In the image bellow how is the voltage drops found and the current in the meters, what is the formula? and if instead of a capacitor an inductor is used ...
0
votes
1answer
36 views

Electronics by Example [closed]

I am interested in learning more about electronics. I know some basics about resistors, capacitors, transistors, and diodes. I would like to learn more about things such as operational amplifiers, ...
0
votes
1answer
28 views

Voltage wave form across a DC motor driven by a transistor with pwm

Above is the simple implementation for a DC motor control with pwm. I was expecting to see a square wave with a Vmax when Q1 is ON and zero when Q1 is OFF like the one here: standard pwm But ...
0
votes
1answer
65 views

Measuring Current in 12V DC Fan

I am trying to measure the current of a DC computer cooling fan (Intel E18764-001) at various volts. Its rated specs are: 12V 0.20A. Check it out here. So I am suspecting that this is telling me: ...
0
votes
1answer
78 views

Calculation of base current resistor resistance for a transistor operating in switch mode? [duplicate]

I have a 9V DC motor and I want to control its speed with an Arduino board with help of a power transistor TIP120. In one of the web-tutorials the writer explains how to calculate the resistor ...
2
votes
3answers
179 views

What is the advantage of a switching over a linear power supply?

I want to build my own switching power supply. I already know how to make a 10 Ampere Linear supply, and I'm wondering if I should bother. What do I have to learn to do a switching supply? What makes ...
9
votes
3answers
568 views

Locking up a DC motor with constant supply a bad thing?

I am working on a little pen plotter project and for one of my motors (which supports the pen) I have used a small DC motor obtained from an old DVD drive. I have noticed that if I supply a constant ...
0
votes
4answers
71 views

How to measure DC Operating Point of a simple transistor circuit

Could someone explain to me how to find the DC Operating point of this circuit? I need to find it by running a simulation and probing the circuit, not solving for it mathematically, and I'm not sure ...
-1
votes
1answer
75 views

Charger light circuit [duplicate]

I have a charger light. It gets charged by 220V AC supply. It can light 5 LEDs. I know that it needs to make the supply 220V AC to DC of lower voltage nearly 5V to 10V. Then it can charge the small ...
0
votes
0answers
41 views

Custom USB 7 port hub PCB dasiy-chain

I had a schematic laid out for a custom USB 2.0 7-port hub I needed to create for a project of mine. It currently uses Ethernet RJ45 sockets to provide power and data to each hub (2 Ethernet ports for ...
0
votes
0answers
28 views

Can I use a power adapter with the same output voltage but different amperage? [duplicate]

I unfortunately burned out a DC adapter for my alarm clock while traveling in Europe. Evidently, it didn't take the 220V well. I ordered another one on Amazon and it just arrived with two problems: ...
1
vote
1answer
183 views

Convert DC 1.5V to 2.7V [duplicate]

How can I convert DC 1. 5V (R20 cell) to DC 2.6V with as much as possible amps? I would like to charge 500F supercapacitor with it. (I can use only 1 R20 1.5V cell).
2
votes
1answer
60 views

How to ON/OFF two fans with 3-state rocker switch?

I have a 3-state switch, It has 3 pins. It can have 3 state as you can see in the picture below. when it's off (i.e on O) the middle pin is not connected to ...
0
votes
2answers
54 views

Bias headphone audio signal for use with digital potentiometer?

I am attempting to control speaker volume via a digital potentiometer, the problem being that audio signal goes both above and below 0V, for regular potentiometers this is no problem but for digital ...
0
votes
3answers
70 views

Can I use this relay for DC

http://www.dx.com/fr/p/ssr-25da-25a-solid-state-relay-white-134494#.VDmPWPl_uap It says AC output but how can this transform DC to AC ? Shouldn't this act like a switch ? If my circuit is DC and I ...
-4
votes
2answers
60 views

frequency of DC current

What is the frequency of dc current, Please tell me, why frequency of DC current is zero in detail. Thank you. I hope anyone really tell me .
3
votes
4answers
145 views

How do I find the voltage range for an unknown DC motor?

I have a small unmarked motor with a burned out speed controller board. I'm able to figure out that the motor is a DC motor because it has two wires coming out of it and there's a rectifier on the ...
1
vote
3answers
69 views

Effect of non-inverting op amp on the AC and DC components of the input

I was wondering what the effect of an op amp like the one in the image below is for an input signal such as \$0.5\sin(2000\pi t) + 0.5\$ V? Are the DC and AC components amplified with the same gain? ...
0
votes
1answer
80 views

Commanding a 12V DC motor with high power (~20A)

I'd like to control a 12V DC motor but it has very high power, around 20A. I was looking for H-bridges but they all support only low power (around 1A) Do I have to build my own H-bridge with high ...
0
votes
1answer
66 views

Participation of DC component in total average power of signal

My task is to calculate participation (in percent) of DC component in total average power of signal from photo: I represented this signal as complex Fourier series: ...
0
votes
2answers
91 views

adding fluctuations to 5V

hobbyist here, hope someone can guide me. I'm using I2C (only have 4 wires{PWR, GND, SDA, SCL}) to communicate with two exterior Circuit (Circuit A, and Circuit B, both have MCUs), which can be ...
0
votes
1answer
141 views

How to replace bulb with LED in a PWM circuit (car)?

I want to replace a light bulb in a Peugeot 308 SW with a LED. The bulb works (lights) normally, but the LED blinks. I thought they are controlling the bulb in alternative current but my digital ...
2
votes
3answers
84 views

Splitting DC power supply risk?

I am looking into taking the power supply 12V output of my PrintrBot and plugging a very simple parallel circuit with some LEDs. I know I can connect a parallel circuit similar to this Splitting a ...
1
vote
2answers
256 views

How to make a 12V DC variable voltage supply with more than 30A output?

I have a SMPS capable of outputting 33A at 12V and I would like to make it have a variable output with full current potential, or close to it. Now, Is it possible to do it with a PWM-controlled ...
0
votes
3answers
147 views

What does an inductor's current stabilize to in DC?

As you can see from the below graph, after an inductor is turned on, the current is stabilized to approximately 6.5mA. My question is: what does the 6.5mA represent? Where did that number come from? ...
0
votes
1answer
124 views

Help me hack this speaker, where would I introduce DC voltage

I have a speaker that runs off of AC (there is a switching converter within the speaker) I'm attempting to convert it to battery power, From my understanding the speaker runs off of 5V (someone else ...
2
votes
1answer
61 views

Difference between DC operating point and Transient operating point

I've been simulating a circuit using synopsys and I'm just wondering what's the difference between DC operating point and Transient operating point?
0
votes
3answers
70 views

Electrical resistance converted to wire temperature

I'm trying to get a formula that I can reuse to help me determine wire size and properties. The goal is to heat a 430' wire between 40-100F using 12 volts and 10 amps of direct current. Everyone is ...
-1
votes
1answer
25 views

Cumulatively excited and Differentially excited DC generator

Is a cumulatively excited DC generator long shunt or short shunt motor?
0
votes
1answer
48 views

Equivalent sequence/stepper relay to “FINDER - 20.21.9.012.4000”

I am currently looking at this relay: FINDER - 20.21.9.012.4000. Which is step relay, that makes contact AC output active with coil input DC (12V) [which i need]; and disconnects output when coil is ...
7
votes
4answers
2k views

What are the highest DC and AC voltages or currents that can be considered as safe?

By safe I mean safe for us when we touch a wire that is not insulated. I have heard that human body resistance is normally 50k Ohm when dry and 20K Ohm when wet. Therefore, these voltages or currents ...
0
votes
1answer
33 views

Convert a non-isolated converter to an isolated converter

Is there a way to convert a non-isolated converter(such as R-78C5.0-1.0) to an isolated converter.
1
vote
1answer
57 views

Making use of bike battery to charge mobiles without any other power resource? [closed]

I need to make my mobile charging in bike, while I go long tours. Actually the bike battery has DC 12-9 volts power and I saw on the phone charger that there is DC 5 volts (or) can I connect the ...
0
votes
2answers
68 views

How to purchase the right transformer for an electronic device [closed]

I just purchased an IP telephone that comes with no power transformer. I think the manufacturer assumes that buyers will be using power over ethernet. On the back of the phone where the power jack ...
0
votes
1answer
37 views

triac DC ground and AC live

In this example of using a 3Q triac, could the AC voltage flow into the DC terminal?
2
votes
2answers
82 views

Using an AC plug for DC current

If I have a plug that is rated 10A @ 250V AC, is it safe to assume I can use it at 10A @ 12V DC? Could it be used at higher current or should its maximum be lower for that matter? Thanks!
0
votes
2answers
124 views

How to find current across a resistor using Thevenin Theorem

It's my first question here. How to find the current through 3 ohm resistor using Thevenin theorem?
-3
votes
2answers
113 views

Why does AC Current exists? [closed]

I need to know why does AC Current exists? And why not only DC current exists? Most devices needs DC current. I know that DC current is much dangerous then AC current. because of it is alternating ...
9
votes
10answers
2k views

Avoiding DC voltage drop over long distances

I am trying to power my IP camera over a long distance from the power socket (about 10m). The included power adapter, rated for 5V 2A is about 1.5m long. I cut the cable and extended it using a ...
9
votes
6answers
2k views

DC adapters: why so few amps?

If I have a device that draws 5 amps at 12 volts, I can use any 12 volt DC adapter that can provide at least 5 amps. Why don't all DC adapters have the capacity to provide loads of amps!? If all DC ...
0
votes
2answers
63 views

LM2596 minimum input voltage question

I'm trying to feed the LM2596 (DC to DC) booster a 9V battery. Now, I see that it has a minimum voltage required of 3V. My question is this: What happens when my 9V battery drops below 3V? Would ...
0
votes
2answers
92 views

Power supply with 10 VDC and 2mA

I have device need 10 V DC and 2 mA, can I use DC battery? For example, two batteries with 5 V DC and 1000 mAh?
1
vote
1answer
146 views

24V to 5V DC conversion for Raspberry Pi

I'm trying to power several devices off of a breadboard. For simplicity I want to power these all from the same PSU. The highest voltage amongst the devices is 24V. I was looking to use a 24V 2A ...
0
votes
1answer
95 views

How to supply multiple 12V DC 3 amps motors?

I need to supply four DC motors 12V @ 3 amps with a battery pack. I was wondering which characteristics should have an hypothetical battery pack to supply all four motors together. How many volts ...
1
vote
0answers
76 views

Insufficient Power when using one power source vs two [duplicate]

So I've been working on a wireless remote relay switch using several components and have struck a break wall. The issue I'm having is that the D0 siginal output triggers the relay but only at short ...
1
vote
2answers
106 views

Using a DC voltage as the base for a transistor to amplify AC Voltage

I'm a little new to electronics, particularly transistors, so I don't know a lot of the different types and inner-workings of them. I have a diagram which, hopefully, will gradually increase the ...
2
votes
1answer
112 views

Electric motor will only start turning at lower voltages

I have a tiny DC motor directly connected to this power supply. The motor starts just fine when the supply is set to 4.5V. I can then change the voltage to 6V and it continues to run just fine. ...
4
votes
1answer
194 views

Headphone output: DC Bias?

Need some electrical advice, as my days of my Electrical Engineering degree are well behind me... I have 4 PMR446 radios ("walkie-talkies"). They work great, but when using an earpiece, every-time ...