DC circuits Interview Questions 

I've got 300mV at 1KHz going in, but I only need to measure the DC values. These values are VB, VE, VC, and VCE. The main one I don't know how to measure with my meter is VB. I'm using a transistor with Beta of 100 and the specific transistor 2N3904.

I calculated a value of 3.8V for VB, but I just can't seem to get the right measurement.

Any help at all will be greatly appreciated. I will choose a best answer.

Hello. Thank you for stopping by.
I need to design and build a little board that will close a relay via pushbutton (while ignoring an interrupted IR sensor), then count 35 interruptions of said sensor, opening the relay upon seeing the 35th count.

For perspective on what I'm doing here: this system is going to count the number of rotations of a gear then power down the DC motor driving the mechanism upon seeing the desired number of rotations.

Need schematic for controlling car window motor. I am using an H-Bridge (EP2-3N1S with schematic http://www.worldproducts.com/pdfs/ep2.pd... )
Followed the following directions
- Connect pins 1 & 8 to the DC supply
- Connect pins 4 & 5 to the motor leads
- Control the motor forward & reverse rotation by energizing either side of the relay (pins 2&3 and 6&7), but not both at the same time (otherwise you short the supply).
Using toggle switch that provides a mutually exclusive "high signal" when pressing up/down, i.e. no possibility of sending shorting supply.

What I'm tried doing (however, need resistors/capacitors, I think)
1. Hook pin 1 to GND, pin 8 to VDD
2. Hook switch's GND to Pin 2 and Pin 6
3. Hook switch's "UP" to pin 3
4. Hook switch's "DOWN" to pin 7

I tried doing the above - when I connected the DC supply to pins 1 and 8 the wires started smoking (melted their casing). A multimeter confirmed that pins 1 & 8 are shorted, now I'm not sure how the H-Bridge works. Thanks

I am designing a science project. I want to connect a red LED, a yellow LED, and a blue LED to a DC voltage source I want to demonstrate the effect on the lights when the voltage is reduced. Please explain the math to calculate the ohms and which wiring method is the simplest to use that will not adversely effect the life of the LED.

In a series-parallel circuit is it possible for the current at a certain point in the circuit to be greater than the total current of the circuit?

Here's an example of what I'm talking about:

http://electropart.info/images/series%20...

Is it possible for the current through R3 to be great than the total current of the circuit (RT) ?

i have electricity class and have problem answering these questions please help me the chapter were on is Sources of electricity , Chemical Energy


1) By generating electricity through the use of chemicals and their reation with other material - You have created _____________


2) The simple ______________ is a good example of chemical energy production.

3) _______________ material , in a cell provides a path for electricity .

4)the chemical inside a dry cell react with the _____________
and the carbon rob to produce electricity.

5)_____________ lights are a common application of dry cell .

6) DC is an abbreviation for ___________________

7) As discussed in previous units Electrons travel from _____________ to ______________


8)The flow of electrons in a circuit is called ______________


9) Childern's toy, cell phone use _________________
as a source of electricity.

10)An instrument used to test for broken wires or burned out (open) fuses in ___

i have electricity class and have problem answering these questions please help me the chapter were on is Sources of electricity , Chemical Energy

6) DC is an abbreviation for ___________________

7) As discussed in previous units Electrons travel from _____________ to ______________


8)The flow of electrons in a circuit is called ______________


9) Childern's toy, cell phone use _________________
as a source of electricity.

10)An instrument used to test for broken wires or burned out (open) fuses in ___

This is the power supply I have choosen:
ThermalTake / PurePower W0100RU / 500-Watt / ATX 2.0 / 120mm Fan / 20/24-Pin / SATA-Ready / PCI-E Ready / Power Supply
These are it's specs
Form Factor: ATX
Wattage: 500-Watt
+3.3V: 22 A
+5V: 32 A
+12V 1: 14 A
+12V 2: 15 A
-12V: 0.3 A
+5VSB: 2 A
20+4-Pin Connector: 1
4-Pin P4: 1
6-Pin PCI-Express Connector: 1
4-Pin Floppy Connector: 2
4-Pin Peripheral Connector: 8
SATA Power Connector: 4
AC INPUT 115V/230V - 60/50Hz
DC OUTPUT +3.3V +5V +12V +12V -12V -5V +5VSB
500W Max
Combined
Watts 22A 32A 14A 15A 0.3 - 2A
500W
Features
Complies with ATX 12V 2.0 Version.
Support 6-pin PCI-Express, 4 SATA, and 20+4 pin connector.
Low noise 12cm fan and mirror effect casing
Protections against Input Protection, Over Power, Over Voltage, Short-Circuit, and No Load Operation.
UL, CUL, TUV, FCC, and CB certification .

Locomotives that use Dynamic Braking with DC traction motors excite the field coils of the motors and turn them into energy producing generators. AC induction motors don't have that option since there are no windings on the rotating armature and there are no slip rings. When used as a traction motor, there are short circuited windings on the rotating armature that produce magnetic fields when rotated in magntic flux fields produced by three phase rotating fields in the outer windings. It would seem that for these traction motors to produce electricity that they must have additional windings on the rotating armature or permanent magnetics installed. Other articles on AC locomotive dynamic braking say that an induction motor is used with no slip rings. If so then how can the traction motor be turned into an alternator?

1.Give two reasons why a faint display on a CRO is better than a bright one.
2.Which is more accurate for measuring dc voltage - a $300 multimeter or a $2,000 oscilloscope?
3.When could an oscilloscope be more useful than a multimeter?

4.If the original voltage source is 14 VRMS what is the peak-to-peak voltage supplied to the circuit?
5. What causes the changes in the waveform of the output voltage for a full wave rectifier ? Explain.

i have electricity class and have problem answering these questions please help me the chapter were on is Sources of electricity , Chemical Energy

6) DC is an abbreviation for ___________________

7) As discussed in previous units Electrons travel from _____________ to ______________


8)The flow of electrons in a circuit is called ______________


9) Childern's toy, cell phone use _________________
as a source of electricity.

10)An instrument used to test for broken wires or burned out (open) fuses in ___

I have four DC voltages that I want to monitor with an external device: +5V, +12V, +15V, and -15V. I have an ADC which allows input voltages between 0 and 4.096 volts. I've set up a voltage divider for each of the positive voltages, targeting each to about 3V input into the ADC. I've added a capacitor to reduce transients and a zener to help prevent over voltage.

I need to determine a way to monitor the negative voltage. I've considered creating a voltage divider between one of the positive voltages and -15V, again targeting 3V for my ADC input. If I do, I will need to take into account any fluctuation on the positive supply when determining the value of the negative supply. I will also need to protect against over and under voltages. Unfortunately, using this method will reduce my resolution and fails if the positive supply is gone.

Does anyone else have a cleaver way to monitor the negative voltage without requiring the use of my positive supplies to power the circuit?

Hi All,

Need some advice on building a wind generator.

I have a 24V 100watt DC motor which delivers about 6amps.

I have tested this by attaching to a drill and measuring the output using a variable load and monitoring the voltage.
OK so far.

Next steps are

** to hook a 12Volt regulator suitable to charge a Lead Acid boat battery. Any circuit diagrams are welcome.

** Attach a suitable set of blades to drive the motor. I have a geared pulley arrangement that allows me to alter the drive ratio as needed. My biggest problem is I have very little knowledge on blades. ie. number required, length and pitch (variable or not). Also I'm trying to keep the overall diamater down to 3 feet or less.
Can I use a propeller from a remote control aircraft? or is there a simple way to build what I need - composite materials preferable, aluminum as a second choice.

Appreciate any feedback.. BTW this is something I'm doing using recycled materials with my son as a green project....

Hi everyone. I have built a special housing for an older camera which takes a 6V Lithium (K28L) battery.

Because of reasons I can't go into here, I need to hard-wire an external longer-life battery pack to the contacts in the battery compartment. Can I safely use 4 AA batteries? Or a 6V AC-DC adapter? My concerns center around the current (amperage) provided by using higher-Amp power sources.

The module I've built makes it impossible to access the battery compartment once the camera is in place, and the limited lifespan of the K28L battery is severely inadequate for the project I'm shooting with the camera.

Is there some sort of inline adapter I can build into the circuit to provide the correct current, or will the amperage draw be dictated by the camera itself?

I should have taken an electronics course, but I burned up all my elective credits on photography classes...

My next mission is to find the Excedrin.

Thanks in advance for your help!
Darin

im looking for an electrical component that limits voltage. ive been searching the internet for an hour and i cant find it. I want the voltage (DC) to be able to fluctuate freely up until 12 volts.. i want the signal to be limited to 12 volts... once it goes over 12 volts it should stop at 12 volts and stay there until the voltage drops back to under 12 volts. I dont want a voltage regulator because i need the voltage to be able to fluctuate below 12 volts... i tried to explain it as good as possibe, does anybody know where i can get one of these, or has anyone even heard of them? also if anybody knows an electrical circuit i could make to do this it would be greatly appreciated.