Resistor dan Kapasitor

How to read Resistor Color Codes

First the code

Black	Brown	Red	Orange	Yellow	Green	Blue	Violet	Gray	White
0	1	2	3	4	5	6	7	8	9

The mnemonic

Bad Boys Ravage Only Young Girls But Violet Gives Willingly *

Black is also easy to remember as zero because of the nothingness common to both.

How to read the code

First find the tolerance band, it will typically be gold ( 5%) and sometimes silver (10%).

Starting from the other end, identify the first band - write down the number associated with that color; in this case Blue is 6.

Now 'read' the next color, here it is red so write down a '2' next to the six. (you should have '62' so far.)

Now read the third or 'multiplier' band and write down that number of zeros.

In this example it is two so we get '6200' or '6,200'. If the 'multiplier' band is Black (for zero) don't write any zeros down.

If the 'multiplier' band is Gold move the decimal point one to the left. If the 'multiplier' band is Silver move the decimal point two places to the left. If the resistor has one more band past the tolerance band it is a quality band.

Read the number as the '% Failure rate per 1000 hour' This is rated assuming full wattage being applied to the resistors. (To get better failure rates, resistors are typically specified to have twice the needed wattage dissipation that the circuit produces) 1% resistors have three bands to read digits to the left of the multiplier. They have a different temperature coefficient in order to provide the 1% tolerance.

At 1% most error is in the temperature coefficent - ie 20ppm.

We now have a program that calculates the minimum error on resistor dividers of up to 4 values. See Resistor for details.

See our Capacitor Wizard
How to read Capacitor codes

How to read a capacitor

Reading capacitors requires for you to have the following information:

Printing from the capacitor
Type of capacitor

If the printing from the capacitor has the complete, obvious value on it, like 3,300 uF, you are home free and don't have to think any more. That is typical only for large valued capacitors with lots of space for printing. Some tantalum capacitors have this as well, though, and they aren't so big. In general, it helps to know what type of capacitor you have so that you can at least figure out about how large the value should be.

But down to business.

Typically, the numbers are in a mn(nnn) x 10^3 format where you have some group of significant digits followed by a single digit multiplier (i.e. 332 corresponds to 33 x 10^2 or 3300). BUT, they don't tell you what the base value is. ALMOST ALWAYS, this base value is pF. Why? Well, nF doesn't sound cool, I guess and by the time something becomes uF or mF sized, you can just print the whole number on the capacitor. Some capacitors are always going to be exceptions to this rule, so you need to pay attention. For example, some of the film capacitors are marked .047; what is .047? Well, .047 is .047uF. Others in the box are marked 473, which means 47 x 10^3 pF or 47nF or .047uF, the normal designation. Also, I've run into some silver mica caps that were marked 10 (as in 10pF, not 1 x 10^0 or 1 pF). It helps to know what capacitance value to expect based upon the physical size of the capacitor in these cases.

Table of typical ranges of values for different types of capacitors:

Type of capacitor	Typical range of values	Working Voltage Range
Silver Mica
Ceramic:
Single Layer	1pF - 47nF	50V - 6KV
Multilayer or Stacked:
C0G/NP0	10pF - 27nF	50V - 200V
X7R	1nF - 580nF	50V - 200V
Z5U	1nF - 2.2uF	50V, 100V
Metallized Film:
Polyester	1nF - 15uF	50V - 1500V
Polycarbonate	100pF - 15uF	63V - 1000V
Polypropylene	100pF - 10uF	63V - 2000V
Polystyrene	10pF - 47nF	30V - 630V
Metallised paper	1nF - 0.47uF	250VAC
Electrolytics:
Aluminum Oxide	.1uF - 68000uF	up to 450V
Tantalum Bead	0.1uF - 150uF	6.3V - 35V

Blah, blah, blah

How are capacitors alike and different?

Capacitors from left to right: 3.3 microfarad polypropylene, adjustable trimmer cap, .0022 microfarad polyester, 20 picofarad ceramic radial capacitor, 15 picofarad ceramic axial capacitor.

ESR:

ESR is the equivalent series resistance of a capacitor. An ideal capacitor would have only capacitance. As you remember, all conductors have resistance. In a capacitor, there are multiple conductors like the wire leads, the foil and the electrolyte. The resistance of all of the conductors contribute to the capacitor's series resistance. It's essentially the same as having a resistor in series with an ideal capacitor. Capacitors with relatively high ESR will have less ability to pass current from its plates to the external circuit (to the amplifiers in the case of stiffening capacitors in car audio). Low ESR is desirable when using a capacitor as a filter.

ESL:

ESL is the equivalent series inductance of a capacitor. Since most electrolytic capacitors are basically a large coil of flat wire, it will have even more inductance than it would have if it were flat. This inductance, along with the small amount of inductance from the wire leads, will make up the ESL of the capacitor. The ESL is essentially the same as having an inductor in series with an ideal capacitor. Low ESL is desirable when using capacitors for filtering purposes.

Leakage:

Even though a capacitor's plates are insulated from each other, there is a small amount of 'leakage' current between its plates. This current is generally insignificant but will cause a capacitor to slowly discharge with no external circuit path between the capacitor's leads.

Note:

Some large capacitors used in car audio systems have a digital voltmeter on them. Some of these displays will have a remote turn on lead to turn on the LED display. Others will have a timer that will turn the display off after a few minutes. If, in either case, the capacitor's positive lead was removed from the power source (and the display remained on), the capacitor would be quickly discharged by the display. This is not the same as the leakage current that we previously discussed.

Film Capacitors:

Many low value capacitors (less than 1 microfarad) will have a plastic type of insulator (polyethylene, polypropylene...) between the plates. Sometimes the plates are actually a metallized layer bonded onto one side of the plastic material. Multiple layers of the metalized plastic meterial make up the capacitor. Adding layers or increasing the size of the layers (without increasing the thickness of the layers) will increase capacitance. The following diagram is an incredibly generic film capacitor. You can see the dark blue insulating film between the cyan and violet plates. The plates are soldered to one of the terminals on one end of the plates. Half of the plates are soldered to terminal A and the other half of the plates are soldered to terminal B.

Electrolytic Capacitors:

Electrolytic caps are more complex than film capacitors and are generally used for larger capacitance values (0.47 microfarad and higher). The electrolytic capacitor generally consists of 2 layers of aluminum foil with a layer of paper material between the plates. It looks a little like this:

Electrolytic Capacitor Foil:

The aluminum foil that makes up the plates in the electrolytic capacitor is treated in a few different processes to make it work properly and more efficiently. The most important process is the anodizing of the foil. Anodizing is a process that forms a very thin layer of aluminum oxide on one or both sides of the foil when the foil is immersed in an acidic solution and direct current is applied to the foil (one lead of the DC power supply is connected to the foil and the other is connected to a conductive plate in the acidic solution). This layer of aluminum oxide is the dielectric (insulator) and serves to block the flow of direct current. To increase the surface area on the foil (and ultimately increase capacitance), the foil can be etched by a chemical process. This would be done before the anodizing.

Paper Element and Electrolyte:

The paper element serves to hold the electrolyte in place. The electrolytic solution (generally ethylene glycol and ammonium-borate) can vary in content but must generally serve a couple of purposes. First and foremost, it must be electrically conductive to help pass the electrons from one plate to the other (the glycol part of the solution does this). Secondly it helps to heal any areas of the dielectric that become damaged (the ammonium-borate does this). If the conductive properties of the electrolyte were absent, the capacitor's value would be drastically reduced. If the healing properties were absent and the anodized coating was scratched or otherwise damaged, the capacitor would leak DC from plate to plate. The healing properties greatly increases the useful life of the capacitor.

Reverse Voltage:

Electrolytic capacitors generally have a positive and a negative terminal. As we said earlier, the plates (foil) of the capacitor are anodized with a DC current. This anodizing process sets up the polarity of the plate material (it deteremines which side of the plate is positive and which is negative). We also said that part of the electrolyte was to help heal a damaged plate. Since it has the properties to heal a damaged plate, it has the ability to reanodize the plate. Since anodizing process can be reversed, the electrolyte has the ability to remove the oxide coating from the foil. This would happen if the capacitor was connected with reverse polarity. Since the electrolyte can conduct electricity, if the aluminum oxide layer is removed, the capacitor would readily pass direct current from one plate to the other (it would basically be a short circuit from one plate to the other). This would, of course, render the cap useless.

Over Voltage:

All capacitors have a voltage rating. This tells you how much voltage the dielectric (insulator) can withstand before allowing DC to pass between its plates. Sometimes a capacitor has a working voltage (i.e. WVDC working voltage DC) and a surge voltage. The working voltage tells you how much voltage the capacitor can withstand long term (for the normal life of the capacitor). The surge voltage is the voltage is can withstand for short periods of time. Generally, if too much voltage is applied to a capacitor, it will fail. In electrolytic capacitors, the forming voltage (voltage used to anodize the plates) and the thickness of the paper element determine the working voltage of the cap. In film type capacitors, the insulating material (polyethylene, polypropylene...) will determine the maximum working voltage.

16 Volt Capacitors vs. 20 Volt Capacitors:

As you've likely noticed, large 1 farad (and 1/2 farad) capacitors are available in both 16v and 20v versions. As was said above, the voltage rating tells you how much voltage the capacitor can withstand. It does NOT tell you how much voltage it will have when connected to your system. If both a 16v and a 20v capacitor are conected to the electrical system (with a voltage of 14.4 volts), both the 16v capacitor AND the 20v capacitor will have exactly 14.4 volts. The voltage on the capacitor will be the same as the circuit to which it's connected. In this situation, both the 16v and the 20v capacitors (which have identical capacitance ratings) will hold precisely the same amount of energy. If (IF) the capacitors were charged to their maximum working voltage, the 20v capacitor would hold more energy because it can survive higher voltage. As you can see in the diagram below, all of the electrical components have the same level of water in them (they have the same voltage). If you continue this analogy, you'll be able to imagine that the lower voltage capacitor would 'overflow' if the voltage would go too high (above 16 volts). The 20 volt capacitor could accept a higher water level (voltage) before it overflows. You can also see that when the capacitors are fully filled, the 20 volt capacitor can hold more water (energy). But... in this situation (and in a car), they hold the same amount of energy.

As a side note... The volume of water that a cylinder can hold is equal to the surface area of the cross section of the cylinder (which is analogous to the surface area of the capacitor's plates) multiplied by the height of the cylinder (which is analogous to the voltage that the capacitor's dielectric (insulator) can withstand). Increasing the surface area and/or height of the cylinder (the maximum voltage rating) will increase the maximum volume (charge) the cylinder can hold.

Overheating and Venting:

An electrolytic capacitor will generally overheat if subjected to adverse conditions such as overvoltage or reverse polarity. This will cause the electrolyte to boil off which will create pressure in the sealed aluminum can that envelopes its internal components. If there were no form of controlled venting, the capacitor would eventually explode. For safety's sake, capacitor manufacturers employ some sort of pressure relief that will fracture before the capacitor's aluminum enclosure. On smaller capacitors, the vent are simply a few stamped lines in the top of the capacitor. The stamping weakens the aluminum casing slightly and allows venting when the capacitor's internal pressure reaches dangerous levels. The other type of vent (used on very large capacitors) is a plug that will blow when pressure reaches dangerous levels.

Stiffening Type Capacitors:

A stiffening capacitor is connected to the amplifier much the same way a battery is. This means that the capacitor's positive terminal is connected to the amplifier's positive terminal (which also means that it's connected to the battery's positive terminal). The same is true of the capacitor's negative terminal (the cap's negative terminal is connected to chassis ground with the amplifier's negative ground terminal). Like this...

Stiffening capacitors are used as a sort of electrical shock absorber. As voltage starts to rise, the capacitor will absorb energy which will tend to keep the voltage from rising as quickly as it otherwise would. If the voltage starts to fall, the capacitor's stored energy will flow out of the capacitor to try to keep the voltage up. A capacitor's ability to absorb/release energy from/to external circuits depends on the capacitor's specs (capacitance, ESR, ESL...), the output impedance of the power source (alternator and power wire in this case) and the circuit's input impedance (into the amplifier's power supply).

Power Source with NO Capacitor:

In the following diagram, you can see that the output voltage (red jagged line) of the power supply is not very steady (with respect to the white reference line). This variation may be due to some defect in the power supply or from varying current draw from other devices that might be connected to the power supply. You can see that the capacitor is NOT connected to the power supply.

Power Source with Capacitor:

In the next diagram, you can see that the capacitor is connected to the power supply and the voltage is much more stable (smaller ripples). The actual amount of smoothing would depend on a lot of things like the source's output impedance, the resistance in the wire and the current draw from other devices.

Power Source with Series Resistance:

The following diagram shows how series resistance (not ESR) allows the capacitor to smooth the voltage even more. The series resistance will allow the cap to smooth the voltage but would cause a voltage drop if current is drawn from the capacitor. Some low current power supplies may be designed in this way to provide a very smooth output voltage. This will generally only work well if the current draw is constant and known when designing the power supply.

Stiffening Caps and Car Amplifiers:

The following diagram shows how the voltage could drop if the alternator's regulator couldn't react quickly enough to prevent a voltage drop. You should notice that the capacitor is not connected. The white line is the alternator's regulated voltage (approximately 13.8 volts). The dips are where the current draw is high. The deeper dips are points where the current draw is even higher.

The diagram below shows what a stiffening capacitor is supposed_to_do for a car audio system. You can see how the ripple is reduced now that the capacitor is connected. The dips in voltage are smaller. If the capacitor does its job, the added voltage (less voltage drop means higher voltage available to the amplifier) would give you more power output, especially with amps with unregulated power supplies. You probably noticed that I said 'supposed_to_do' earlier. This is because there has been some discussion as to whether a capacitor is a help or a hinderence when it comes to keeping the voltage at a higher level than without it. Of course, if you ask someone that's spent more than $100 on a capacitor if it helped, they'll tell you that it has. Why on earth would someone 'fess up' to wasting that much money on 'snake oil'. I've yet to see a capacitor increase the SPL in any system.

NOTE:

For maximum benefit, you should keep the length of wire between the capacitor and the amplifier to a minimum. Anything (wire, distribution blocks, fuses...) between the capacitor and the amplifier will reduce the capacitor's ability to quickly supply the current needed by the amplifier. Of course, if you have multiple amplifiers and want the capacitor to benefit all of them, you'll have to connect it to the distribution block.
TECH TIP:

Charging large capacitors:

When connecting a large capacitor (1/2 farad or larger) to the 12 volt source, you may want to charge it slowly before making the final connection to the power wire. Most capacitors come with a resistor to charge the cap slowly. If you're working on your system, and disconnect the capacitor, the cap may get discharged (something might accidentally touch across the terminals or it may partially self discharge over time). If you can't find the original resistor to recharge the cap, you can recharge it with a standard test light (you know, the one with a light bulb, not one of those fancy pants test lights with LED indicators). There's a somewhat helpful demo near the bottom of the page.

If you don't have a test light and want to use a resistor to charge or discharge your capacitor, use a ceramic encapsulated high power resistor like the one below (I'd recommend using a resistor rated for 10 watts or more and about 20 ohms). If you use a small resistor (i.e. a 1/4 or 1/2 watt) of too low value (less than 100 ohms), it may get hot enough to seriously burn your fingers.

Ruler values are in inches.

REASON:

The reason you may want to charge a cap slowly is to reduce the arcing involved with fast charging. This arcing won't hurt the cap but it might damage the chrome or gold finish on the connectors.

This demo shows how the test light brightness indicates the charge level in the capacitor. Put your cursor over each capacitor charge status and watch the brightness of the test light. If you have a slow connection, it may take a second or two for each image to load. Click on the amplifier below and the image's position will be optimized.

Charge Status
Completely DIScharged | Half Charged | Completely CHARGED | Finished

Discharging the Capacitor:

If you're going to remove your capacitor for some reason, you may want to completely discharge the capacitor to prevent creating a hazardous situation. To discharge the capacitor (after it's disconnected from the system), simply provide a path for the current to flow from one terminal to the other. You can use either the test light or the resistor. After it is discharged, you may want to connect the terminals together with a piece of wire or resistor. Some large capacitors will act like a battery and develop some small voltage across its terminals. Since the capacitor is likely a large capacitor (over 1/2 farad), the small voltage could be dangerous. Even if your capacitor's design doesn't cause it to develop a significant voltage when not in use, leaving the terminals connected will leave no doubt whether the cap is charged or not.

Charging with a Resistor:

If you need to know how long it will take to charge a capacitor with a given resistor, you can use the following calculator. The output data tells you how long 'one time constant' is (time to reach 63.2% of the difference in voltage between the capacitor's voltage and the supply voltage). It also tells you how much time it will take the capacitor to become charged. Lastly, it tells you the maximum power dissipation across the resistor (use this value as a guide in selecting a resistor).