ENGINEERING.com Electrical Engineering

Effect of Lightning Strike on Electrical Lines

Mirjan — Tue, 12 Mar 2013 13:15:49 GMT

can you help me for effect of Lightning Strike on Electrical Lines, on disconnection of their successive, please.

Undergraduate engineering degree

ANTHONY — Mon, 29 Apr 2013 14:52:25 GMT

Hi

I have hopes of becoming an engineer. I have a lot of choices; RPI,WPI,Villanova,Rutgers,Stevens and The College of New Jersey. I have absolutely no idea which to choose, though I am leaning towards Stevens or Villanova. Any thoughts or comments will be greatly appreciated.

Thanks!

Matrix Keypad with MT8870

Mridul Agarwal — Sat, 13 Apr 2013 07:26:52 GMT

Hi!
I have a circuit which have two wires for input , so can anyone tell me how to connect a 4*4 Matrix Keypad with it . Circuit can be found at:-
http://www.instructables.com/id/Cellphone-Operated-Robot-1/step3/SCEMATIC-OF-CELLPHONE-OPERATED-LANDROVER/

Isolation Transformer

KT Sriram — Tue, 05 Mar 2013 01:04:26 GMT

Why isolation transformer is required with UPS ?

Heating wire

G.M. Fisher — Thu, 28 Mar 2013 16:46:24 GMT

Questions: Can low 7.4mW heat 40 gauge nichrome wire? To what temperature assuming coiled wire? Is there a better wire to provide higher resistance that could be heated with low current?

Thanks for any help.

Resistor with DC brush motor

onn201185 — Thu, 28 Feb 2013 05:18:18 GMT

Did anyone know that what is the purpose of a resistor connect parallel to dc brush motor?

why device are used having more current rating than the required current

priyadarshictc — Tue, 26 Mar 2013 02:01:44 GMT

As i am doing a trainee engineer in control pannel industry i saw for a 1 kw motor and 0.5 watt heater there are mpc of 25A contactor of 18A
smps of 10A and motor of 1kw 9A in the pannel and the supply is single phase. SO why this much current ratings are used as it only requires 4a cureent.

Building a Hartley Oscillator - Choosing the tapped inductor value

somethingfree123 — Mon, 11 Mar 2013 08:06:43 GMT

I found this circuit I want to try out but, the diagram I have doesn't show the actual inductor value that I need to use.

In the attached: It shows the turns for L5. So, I assume the critical issue is to make sure I have the proper ratio on either side of the tap. But, I'm not sure. Can anyone help with the correct value for L5?

Also, can anyone help find a source for a tapped inductor like this one? Mouser doesn't let you search by "turns":)

Thanks.

Distribution of Fault Current in Transformers

Ella — Mon, 11 Mar 2013 04:05:03 GMT

Hi!

I am busy studying distribution of Fault currents through transformers, if I have a Wye solidly grounded delta transformer and I have a phase to earth fault on the secondary side of the transformer am I correct to say that Ia, Ib and Ic on the primary side will be 0?

If the secondary delta is grounded with a earthing transformer which is either a zig-zag or wye grounded delta transformer. Will the currents on the first transformers primary side remain 0 if a phase to earth fault occurs?

Any assistance will be much appreciated.

Need a hand with Class A amplifier desgin and simulation..

ckt_Boy — Sat, 02 Mar 2013 20:14:08 GMT

Hi! Good day to everyone! Im a freshman student and i've been working on a project my teacher has given me last friday. He wants me to produce a schematic diagram and a simulation of a Class A amplifier that is a voltage-divider kinda looking with the emitter resistor being bypassed by a cap. The hard part here is the designing part to which i am a newbie. He wants the circuit to have a voltage gain of 4200 & a bandwidth of 20 kHz. The DC source should be 12 V. It's on me (or you) to decide whether BJT or a FET be used as long as the parameters mentioned above can be provided. Lastly, he instructed that if the gain found is less, one can use OP AMP (l have little knowledge on this) for it to be fixed. I will be truly grateful if anyone here can assist me on this problem...Thanks in advance!!!

Double bus switchgear

KT Sriram — Mon, 25 Feb 2013 00:56:25 GMT

Wanted to know;
- Advantages / disadvantages of double bus switchgear
- Which type of industries generally use these

Need to build some type of mold housing for a NAND Flash Chip or a Micro Controller Unit Located on USB Flash Drives

Engineer-3 — Fri, 11 Jan 2013 06:03:31 GMT

Hello,

First of all, I am not an actual engineer. We have some concept ideas and will utilize the employment of an actual engineer once we have more information behind this all. With this said, please forgive my not so technical way of thinking and explaining all of this.

We are attempting to build some type of an enclosure or housing that would allow us to perform chip swaps from 2 duplicate devices.

1. We have 2 identical duplicate USB Flash Drives (Full PCB with components inside of casing).

2. Device #1 is not working due to a failed MCU (Micro Controller Unit).

3. Device #2 is in a working condition.

4. We would like to swap the bad micro controller from device #1 with the good micro controller from device #2.

5. One problem, the micro controller is surface mounted; meaning, all of the soldering points are under the chip. It is hard to properly align all of the connecting points (most of the time there are over 20) with the PCB soldering points due to a visibility issue (we cannot see under the MCU as it is being connected to the surface of the PCB).

6. At this point, we have 2 different options.
a) Purchase expensive imaging equipment that will allow us to see through the PCB and chip to allow for proper alignment. Not sure if there is equipment like that out there? I am envisioning something along the lines of a X-Ray machine?? Maybe some type of imagining equipment that would allow us to accomplish this is not too expensive?? Please give any suggestions as to what the name of the equipment could be (brand name, links etc...).
b) Create some type of housing or mold that would temporarily attach to the PCB securely. Basically, a mold that would be the perfect size to allow us to just place the chip inside of this mold and then heat the whole board with the MCU Chip inside of housing. After heating, the good Micro Controller chip would be properly attached to the PCB and this temporary mold (housing) could be removed.

7. And whalaa, we have a working USB drive again as the bad MCU was replaced with a working one.

8. Attached is an image of a USB device with a surface mounted controller.

Again, please excuse my not-so technical verbiage in this write up.

Any and all comments, suggestions and questions are appreciated.

Thanks ahead,

Engineer-3

Need help on building a filter for power supply

einstein2nd — Sat, 05 Jan 2013 17:59:33 GMT

I am building a power supply from scratch and need help on selecting the right size inductor and capacitor for an LC filter.

The power supply consists of: transformer, full wave rectifiers, filters, and regulators.

Transformer specs:
Input: 110 VAC 60 Hz rated @ 15 amps;
Output: 15 VAC 60 Hz rated @ 30 amps;

Full Wave Rectifier specs:
bridge rectifiers rated @ 40 amps;

LC Filter specs:
Input: 15 Volt Pulsating DC rated @ 40 amps;

Regulator specs are currently unknown.

I have avionics background but a little rusty on LC filter circuits.
I am trying to flatten out the ripple as much as possible before sending it to the regulator.

I am hoping someone can help me.

Supercapacitors

alexrr60 — Fri, 23 Nov 2012 08:53:08 GMT

Trying to establish the right connectivity of Supercapacitors with Battery Bank. EV will have regenerative braking. Have on hand ten 2.5v 3000 farads Supercaps and currently have them placed as two 12.5V batteries in Parallel with two of the six 12v batteries in the 72v battery bank. How should I connect the regenerative brake system to the supercaps and in turn to the battery bank?

Biomass Energy

georgeamad — Tue, 13 Nov 2012 05:00:11 GMT

Hey all, can anyone advice a good source re different types of Biomass Energy and in particular calculations relating to its domestic usage (heating)?

Thermistor sensor

NemOreo — Mon, 30 Jul 2012 07:50:10 GMT

I'm trying to use a thermistor (2553 ohms at 25 C) sensor to measure temperature. The ultimate goal is to measure temperature with great accuracy. I have set up a voltage divider circuit and calculated the resistance of my thermistor for various temperatures. With the equation: E1=E2(r2/(r1+r2)), r2 is thermistor. And then graphed the data and created an equation to predict unknown temperatures. This doesn't work because everytime I collect data points, I'm calculating a different resistance for the known temperature. Can anyone provide thoughts on collecting more meaningful data, or another way to get accurate data?

Help with UBA2014 lamp driver IC

deval — Mon, 19 Nov 2012 08:22:44 GMT

I am a recent uni grad working as a design engineer and one of our product is using UBA2014 IC. We are having many boards failures because of UBA failures and the failures are catastrophic.. IC it self and many components around it is blown.. If someone wants to have a look at it I will send the diagram.. I somehow couldn't attach it here

Batteries

culloekee — Fri, 09 Nov 2012 00:20:32 GMT

Would like to know how to determine the remaining power margin left in a battery after use. I have a 4Ah nicad battery that was at 30V with a 3A load for 750 seconds. At the end of the 750 seconds the battery voltage was 28.2V. Just want a rough way to calculate, not worried about heating or internal resistance of each of the cells.

Motion Sensor

cdw2152 — Tue, 25 Sep 2012 22:15:14 GMT

Hi,

I was wondering if I could get some insight. Where I currently work our conveyors have zero speed sensors. These sensors sound an alarm if no speed is detected. The issue we have with them is they fall off all the time. The shaft on the conveyor pulley has a hole tap into the end of it which a piece of all-thread screws into. The all-thread is coupled to the shaft on the zero speed sensor.

What I want to do is design, install, and test a sensor that goes off motion. If no motion is detected then an alarm would go off. So far the only motion sensors I can find sound an alarm if motion is detected.

Any suggestions would be greatly appreciated.

Thank You

Chris W.

PLC programming help

abid00 — Mon, 27 Aug 2012 23:30:43 GMT

i need some help with this program which is : write a program with ladder diagram for PLC Siemens s7-200 that operates a pump four days in the week (Saturday-Monday-Tuesday-Thursday) and set it off in the three other days (Sunday-Wednesday-Friday) the program should work for good.