Discharging a Capacitor With a Screwdriver: Tips and Tricks

Capacitors are tiny devices that retain a significant amount of electrical power and pose a potentially lethal threat. And, of course, you don’t want to be electrified while replacing a device’s capacitor.

So, if you’re reading this, you quite probably have a good idea of how to do it. However, there are various “hacks” that you may employ to save time while being absolutely secure. Hence, below are some tips and tricks for discharging a capacitor with a screwdriver!

What is a Capacitor?

A capacitor is a type of device that stores electrical energy. It accomplishes this by establishing an electromagnetic current across two plates. And as a voltage is added to the capacitor, it charges it.

Additionally, a capacitor’s permeability/capacitance measures the number of charges it can hold and is commonly expressed in farads.

In fact, capacitors function similarly to rechargeable batteries in alternating current circuits. So, they serve to store electrical energy and transmit it to other circuit components.

Why Do Capacitors Need To Be Discharged?

Discharging your capacitors is indeed important because they contain electricity and can deliver harsh shocks if touched while still charged.

Additionally, they can hold the voltage in themselves for another few minutes after the current in the circuit ceases flowing. So, here are the two main scenarios wherein you need to discharge your capacitors:

  1. If you are fixing a piece of electrical equipment and therefore need to extract the capacitor from the circuit board.
  2. If you’ve recently changed a capacitor in your gadget and would like to remove any remaining charge that may have stayed.

Safety Precautions to Consider

A capacitor may retain an electrical charge even after a device has been turned off. The more charge a capacitor can store, the bigger it is. Dealing with capacitors with large voltage values (particularly those beyond 100V and with a high capacitance) can be hazardous if the right precautions are not followed.

So, when discharging a capacitor, you must always take measures to prevent any unanticipated risk and/or shock threat to anybody who may operate the device. Hence, the reason why all capacitors should indeed be depleted ahead of any usage.

Safety Steps Before Discharging Capacitors

Check Power Supply

It is critical to always cut off the power source before discharging capacitors while dealing with them. This will aid in the prevention of injuries and accidents. Capacitors can store a significant quantity of energy.

Protective Gears

Like in any other hazardous process, wearing protective equipment is a must. And here are several reasons why:

  • Capacitors may store a lot of energy and, if discharged, can release sparks.
  • When capacitors’ metal contacts touch the skin, they can cause electric shocks.
  • Most individuals find protective gear amusing, but they alter their thoughts when hurt by electric shock or sparks.
  • Goggles and gloves, for example, can assist protect you from these hazards.
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Conduct in a safe environment

Initially, keep in mind that you should be in a well-ventilated place. As you drain the capacitor, ensure no combustible objects or gadgets around you because you are dealing with a potentially dangerous operation involving electricity. Also, you mustn’t touch anything else while you’re discharging the capacitor, or you’ll be shocked.

How To Discharge a Capacitor Using a Screwdriver?

Discharging a capacitor using a screwdriver is easy. However, being precise with each step is critical since this may be deadly even if you’re an expert on this matter. So, the following are the steps so you can safely execute this procedure:

Step 1: Locate the Capacitor

The first step in discharging a capacitor with a screwdriver is locating it. Most of the time, these are located on any electronic device. It can be located in water pumps, air conditioners, washing machines, AC motors, etc., in your house. Other than that, it can also be in your car’s engine.

Since they are important for storing energy and controlling current flow, these are typically found near power supplies. However, If you can’t locate the capacitor, examine your equipment’s schematic diagram or the owner’s handbook.

Step 2: Set up Multimeters

In using multimeters, you must first set the voltage range on your multimeter. Then, switch off the electricity at the socket or disconnect the battery from the circuit.

Now that the battery has been removed, place one multimeter probe on each side of the capacitor’s leads, including positive and negative probes pointing in the same orientation.

In fact, it makes no difference whatever terminal you use as long as it is compatible with all of the other measurements obtained during this procedure.

Simply ensure that the black lead gets into the “-” (negative) socket and the red or blue lead enters into the “+” (positive) socket.

Step 3: Connect Leads to Screwdriver

In connecting the leads to your screwdriver, you must first remove approximately 12 inches of insulation from each tip of both leads. Then, twist each wire (negative on black and red) around the proper screwdriver head.

Lastly, check that the metal and wire are in excellent alignment; if required, use pliers to twist wiring more securely around screws.

Step 4: Monitor Multimeter Display

As you monitor the multimeter display, take note of it in a notepad if you see a shift. Then, while you contact each terminal, the needle must deflect upward and then drop back, indicating that the capacitor’s power has been discharged.

After contacting every lead, keep on watching the meter for a few seconds to ensure that no remaining charges linger from either side of the wires (which could give you an erroneous reading)

So, if the voltage is reasonably low (less than 50 V), you can discharge it using an insulated screwdriver. Alternatively, use a resistive receiver that can tolerate the voltage.

Step 5: Utilize Insulated Screwdriver

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You can use an insulated screwdriver to prevent contact with the live connections when discharging a capacitor.

Keep in mind that the metal screwdriver blades would now be charged. So, avoid touching any other metal objects unless they’ve had time to cool. A grip made of plastic or rubber will assist in reducing the danger of shock.

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Initially, you must locate the capacitor’s positive and negative connections. Afterward, using an insulated screwdriver, link the positive and negative terminals. Then, hold down the screwdriver for the next few seconds until the capacitor discharges.

Remember that a capacitor discharge might result in a spark or a flash of light. This is quite natural and should not frighten you.

Step 6: Put Screwdriver Across Both Leads

If the capacitor has been discharged, it is now safe to remove the screws from the gadget.

Put the screwdriver through both ends of the capacitor to short both out and avoid unintentional shocks. It will also assist in keeping things structured and make it much easier to deal with later.

Step 7: Check Multimeter Again

After putting the screwdriver in across both leads, you can now remove them from the capacitor terminals, and you can repeat the previous step to ensure that it’s empty.

Check the meter again with a multimeter to measure the capacitor voltage. This ensures that there is no charge in either lead.

Afterward, connect the probes and metal contacts as the order of connection (polarity) is unimportant.

If the result is more than zero, the capacitor has not been entirely drained. The method should be repeated numerous times to verify that the capacitor has been properly depleted.

Other Discharging Tools

Aside from a screwdriver, you can also use other tools to discharge capacitors. Below are these tools and how you can use them as an alternative to a screwdriver.

Pen tool

This is the simplest and quickest method. An elevated resistor in the discharging tool allows the electricity to be discharged fast.

Simply short off the two plates using a pen tool to discharge a capacitor. This will produce a spark, which will rapidly disperse the charge.

It is important to exercise extreme awareness when discharging capacitors since they may store a substantial amount of energy.

Light Bulb

A light bulb can also be used. The bulb has an edge above other instruments in that it contains a light pointer that indicates when the capacitor is full or empty.

First, you will need to take one light bulb that is wired to a bulb socket. After that, attach one wire to the positive terminal and the other to the negative terminal. As a result, the bulb will begin to light up, and when it shuts off, it signals that the capacitor has run out of charge.


A resistor prevents a big current surge from passing through the capacitor, which might destroy it. So, you may avoid any possible difficulties by gently discharging the capacitor using a resistor.

To begin, ensure that the capacitor is disconnected and that no energy is supplied. Then, attach the high-value resistor across the capacitor’s terminals.

Next, connect the resistor’s edges to the capacitor’s metal contacts. Hold until the capacitor is completely depleted. After that, unplug the resistor from the capacitor. Finally, connect the capacitor and turn it on.

Make Your Own Capacitor Discharge Tool

To start building your own capacitor discharge tool, you must first gather these tools:

  • 100 microfarad 450 volt capacitor
  • 100 ohm. 2-watt resistor
  • Crop clip
  • Probe
  • Small steel box

So first, a probe on the upper/left side and the cropped clip on the other. The probe will serve as an external capacitor while the cropped clip will attach to the chassis or the negative terminal.

Generally, the 100 microfarads, 450-volt capacitor, and 100 ohms are inside the box. 2-watt resistor. The 100 microfarad capacitor will be placed straight across the probes at 450 volts. For the spring-loaded momentary switch, it goes via the 100 ohms. 2-watt resistor on the ground.

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So, to discharge the capacitor using this invented tool, attach the cropped clip to the amplifier’s chassis. Then, you can use the probe to probe onto the capacitor with the high voltage or the positive terminal.

After this, you can press the switch for a few seconds, discharging the capacitor through the 100 ohms 2-watt resistor.

As for the 450-volt capacitor, it sits across the probes. This is important for amplifiers if the hum is present, caused by a leaky or faulty capacitor. Then a good test to see if the capacitor has a problem is to clip it on a good capacitor across it.

Then, you can clip the negative on the left side while touching the probe on each capacitor, in turn, to see if the hum goes away. If not, you can turn to the next capacitor until you notice the hum go away.

Frequently Asked Questions (FAQs):

What is the fastest way to discharge a capacitor?

The fastest way that you can discharge a capacitor, as mentioned above, is by using a pen tool. This contains high-value resistors, allowing the current to be discharged immediately.

Is it safe to use a screwdriver in discharging a capacitor?

It is normally safe to discharge a capacitor with a standard insulated screwdriver. But, for electronics with bigger capacitors, such as home appliances, it is advisable to assemble together a capacitor discharge tool.

Does a capacitor discharge on its own?

Of course, a capacitor will ultimately drain on its own if it is not linked to any external power or any other charging equipment (internal battery, for instance). This is caused by the normal passage of electrical current through the dielectric material that divides the capacitor’s two plates.

What capacitors are considered safe from electric shocks?

This question has no answer. Any capacitor can cause you to harm in some way. However, capacitors up to 50 volts cannot cause current to travel through the body and cause death.

Capacitors less than 50V frequently induce stinging, a minor electrical shock, and tingling in the fingertips. Keep in mind that only empty capacitors are completely safe.

How to avoid accidents when working with capacitors?

If not done correctly, capacitors can be hazardous. Hence, below are some of the few tips to assist you to prevent accidents while discharging a capacitor:

  • Before dealing with the capacitor, ensure that it has been discharged. You may accomplish this by connecting the capacitor’s two metal contacts.
  • When working with capacitors, always wear gloves. This will shield your hands from any electrical shocks.
  • When carrying capacitors, exercise extreme caution. They may be rather hefty and can tumble off a table or seat.
  • Never exceed a capacitor’s maximum voltage rating. This can cause an electrical explosion.

Discharge your capacitors with Screwdrivers today!

A capacitor may be gently packed to the required voltage and immediately discharged to deliver the required energy.

Discharging a capacitor can be tricky, especially if you aren’t equipped with the right tools and information. So, given the information above, it’s indeed safe to use an insulated screwdriver in doing so. However, you certainly need a lot of practice to avoid mishaps, especially if you are new to this.