Electronics Basic Symbol (just for kids)

Here are five basic symbols that you will find on electronic wiring diagrams, along with a brief definition. Look them over. When you get to #12 you can see if you remember the name of each symbol.

• Battery--a DC (direct current) voltage energy source.

• Ground--the common or reference point in an electrical circuit.

                             

• Resistor--an electrical component that opposes current.

• Capacitor--an electrical device that can store an electrical charge.

• Diode--a one-way conductor that allows current to flow only in one direction.

   

CCTV camera

Network Camera STC-IPM3096A allows for round the clock surveillance in the "Day" / "night" in all light up 0.4/0.06 lux, and forms an image with resolution up to 1280 × 960 pixels.  It can be broadcast on the network simultaneously two customized stream video M-JPEG format and / or MPEG-4.

In addition, STC-IPM3096A has motion detector, equipped with 2 GB SD-card memory, alarm inputs / output, audio inputs / outputs for audio link between the operator and the area of observation and supports PoE. Setting up the camera can be carried out through a web browser or with the NetStation.IP-camera is capable of transmitting on the network to two video streams simultaneously in the MPEG-4 and / or M-JPEG with resolution settings and the framerate each. In the M-JPEG format with a maximum resolution of the image STC-IPM3096A can reach SXVGA (1280 × 960 pixels.) With frame rate 10-15 fps. Increase framerate flow up to 25 fps in this format by specifying the resolution VGA (640 × 480 pixels.) Or QVGA (320 × 240 pixels.).In MPEG-4 IP-megapixel camera capable of transmitting video VGA-standard full-frame mode Low, Middle, and High. To optimize the video stream in the M-JPEG for bandwidth video, you can choose the degree of video compression: Low, Middle or High.

Record and store video and audio c IP-camera can be carried out on a network video recorder (NVR), PC hard drive or external disk drives and arrays. For temporary storage of data, including anxiety, designed SD-card memory capacity of 2 GB, which is supplied STC-IPM3096A. This IP-megapixel camera can record video on a map constantly, cyclically updating archive as it is filled, or just disturbing video. Efficient operation IP-camera in the security video provided by the hardware motion detector, alarm inputs, which can connect an external alarm sensors, and alarm output, through which you can manage the work of executive device.  Built-in STC-IPM3096A VMD has the three levels of sensitivity and allows you to set up 48 areas of detection of 8x6 square grid elements. In the basic setup IP-camera "reacts" to the alarm event lasting no less than 100 milliseconds, but in order to avoid false positives during her reaction may be increased to 60 seconds. Thanks to the audio input / output cell 

STC-IPM3096A lets you listen to the zone of its installation or to arrange two-way audio with the operator of the security services.

Aircraft Receiver

The Passive Aircraft Receiver is basically an amplified "crystal radio" designed to receive nearby AM aircraft transmissions. The "passive" design uses no oscillators or other RF circuitry capable of interfering with aircraft communications so it should be fine inside the cabin of the aircraft. Nevertheless, check the regulations before using this receiver on a commercial airliner.

New security regulations probably prohibit this device on commercial flights. Do not expect to hear two-way aircraft transmissions with this receiver! It is a short-range receiver only.The detector diode is a 1N5711, HP2835 or similar Schottky detector diode. The 10 megohm resistors provide a small diode bias current for better detector efficiency. The tuning capacitor may be any small variable with a range from about 5 pF to about 15 or 20 pF. The 0.15 uH inductor may be a molded choke or a few turns wound with a small diameter. Experiment with the coil to get the desired tuning range. The aircraft frequencies are directly above the FM band so a proper inductor will tune FM stations with the capacitor set near maximum capacity. (The FM stations will sound distorted since they are being slope detected.) Other capacitor and inductor combinations may be selected to tune other bands if desired. (Try the CB band at 27 MHz.) The LM358 dual op-amp draws under 1 ma so the battery life is quite long. A speaker amplifier may be added to drive a speaker or low-z earphone. The antenna can be a couple of inches if the receiver is near the transmitter or a couple of feet for maximum range. The selectivity is reduce as the antenna length is increased so best performance is achieved with the shortest acceptable antenna. Try increasing the 1.8 pF capacitor value when using very short antennas and decreasing it for long antennas. The receiver could be built into a small plastic box with a short antenna inside.

Battery tipes

Basically there are two types of batteries; starting (cranking), and deep cycle (marine/golf cart).The starting battery (SLI starting lights ignition) is designed to deliver quick bursts of energy (such as starting engines) and have a greater plate count. The plates will also be thinner and have somewhat different material composition. The deep cycle battery has less instant energy but greater long-term energy delivery. Deep cycle batteries have thicker plates and can survive a number of discharge cycles. Starting batteries should not be used for deep cycle applications. The so-called Dual Purpose Battery is only a compromise between the 2 types of batteries.

Battery safety tips

Batteries is dangerous if we treat them wrong.We must think safety when we are working around and with batteries. Remove all jewelry. After all you don't want to melt your watchband while you are wearing the watch. The hydrogen gas that batteries make when charging is very explosive. I have had 2 batteries blow up and drench me in sulfuric acid. That is no fun. This is a good time to use those safety goggles that are hanging on the wall. Sulfuric Acid eats up clothing and you may want to select Polyester clothing to wear, as it is naturally acid resistant. I just wear junk clothes, after all Polyester is so out of style. When doing electrical work on vehicles it is best to disconnect the ground cable. Just remember you are messing with corrosive acid, explosive gases and 100's amps of electrical current.

Move it with a VFD - Part 2

As we saw last time, a VFD can often be used in a motion application where some high torque and variable speed is required. If we apply them properly they are one of the best motor controllers in industry. The key statement there is 'if we apply them properly'.

To apply one correctly we really need to understand the load requirements. Basically, we need to ensure we can supply enough current for the motor so it can produce as much 'torque' as needed.Torque may be a new term for you in the motor world. Generally, we talk about horsepower in the motor world but it relates to torque and that's what we need to discuss in the VFD world.

Torque is a force that produces rotation. It is commonly measured in units of lb-ft (pound-feet). It is the force necessary to cause an object to rotate... Think of a merry-go-round (carousel ride). To get it to rotate by hand you would need to push it with a certain amount of muscle. That 'certain amount of muscle' would be the 'torque'.

If you tighten a bolt with a small wrench it will be difficult. Use a bigger (i.e. longer) wrench and it will be easier to tighten. For example, to tighten the bolt to 50 lb-ft you would have to apply 50lbs of force to a 1ft long wrench. On the contrary, you would have to onlyapply 1lb of force to a 50ft long wrench to tighten it the same.

Many (most?) machinery loads are constant torque loads. Conveyors,compressors, etc are some good examples. Variable torque loads are generally most pumps and fans. A VFD is usually specified for variable torque loads because they can help save energy but they are used forconstant torque loads too.

Peak torque efficiency comes at a certain volts per hertz ratio. As long as our VFD stays at this ratio we can develop the rated torque.For example, let's assume we're using a 460 volt source at 60 hertz.The ratio is therefore:
volts / hertz
460v / 60hz
7.667 v/hz

As long as the ratio stays in the above proportion we can supply the rated torque. So, if the volts fall we'll need to decrease the frequency to maintain the same ratio.

Horsepower is torque with the addition of time and distance. So, it's the torque generated to move something a given distance in a given period of time. It's related to torque by the formula:

HP = (torque * speed) / 5252

For example, if we have 30 lb-ft of torque developed in a motor rotating at 1500rpm we get:

HP= (30 * 1500) / 5252
HP= 45,000 / 5252
HP= 8.57

For reference, if we exert 1 hp we can move 550 lbs in 1 second. If we are just holding the 550 lbs still, we are not exerting any horsepower.There MUST be movement...

No movement would mean no torque which would mean no horsepower. See?
To specify a VFD we need to understand the torque requirements of the load. We need to consider:
1- The torque required to start the motion
2- The torque required to bring the load to speed in a certain period of time
3- The torque required to keep the load moving
4- The torque required when the motor acts like a brake to slow down the load
5- And the peak torque needed by the load

Most folks will use an ammeter to measure the current under all the load conditions listed above and find the peak current drawn. The VFD is then sized to the motor based on the maximum current draw at the peak torque levels plus an extra margin. Notice that the VFD is not specified based on the horsepower ratings of the motor. It's a torque thing..

Move it with a VFD - Part 1

VFD is a Variable Frequency Drive. It works with AC motors and setsthem into motion. It does so by varying the frequency of the voltage
supplied to them. There you go. That's it. Simple... but now let's see
some details.

The VFD controls two factors of the motor... speed and torque. As you
may remember from your school days, torque is a rotational force and
speed is ... well... speed. Combine the 2 and you get into horsepower
but that's a topic for another issue.An induction motor (real commonly used by folks in the industrial
factories of the world) would rotate at a fixed speed that is
determined by the frequency of the voltage supplied to it.

Alternating current (i.e. AC)applied to the motor windings in the
'stator' produces a magnetic field that turns the motor shaft. We vary
the speed of the motor shaft by either changing:
1- The frequency of the AC applied to the windings
2- The number of magnetic poles in the windings

So, using a little math... and I mean a 'little math'... we can
calculate the speed of the motor. Just use the formula:
(120 * frequency) / number of poles = speed

If we supply a 50Hz voltage to a 4 pole motor and use the formula
above we can see that we will be turning the motor shaft:
(120 * frequency) / number of poles = speed
(120 * 50) / 4 = speed
(6000) / 4 = 1500rpm (Revolutions Per Minute)

So, if we examine the formula above a little closer, we can see
that if we want the motor to go faster we can increase the frequency
of the AC voltage applied to the windings. If, for example, we change
from 50Hz to 60Hz in the example above we get:

(120 * frequency) / number of poles = speed
(120 * 60) / 4 = speed
(7200) / 4 = 1800rpm (Revolutions Per Minute)

So, now instead of turning at 1500rpm we're flying at 1800rpm.

How else can we change the speed? Well as we read above we can also
change the number of poles our motor has. So, if for example our
motor had 8 poles in the original example we'd be moving at:
(120 * frequency) / number of poles = speed
(120 * 50) / 8 = speed
(6000) / 8 = 750rpm (Revolutions Per Minute)

So, now instead of turning at 1500rpm we're crawling at 750rpm.

Trouble is, however, that the poles are a physical 'fact' of the motor
so we can't just change them on the fly. We'd have to change the whole
motor! What good is that if we just want the speed to vary?
No good...

So, you can see that the best way for us to change the speed of the
motor is to 'vary the frequency' of the voltage being applied to it.
Can we do that? Sure we can... with a Variable Frequency Drive (VFD)!

Stay tuned as next time we'll see how the VFD actually works along
with it's relationship to our powerful friend 'torque'.