Inductive spiking, and how to fix it!
Why Electrical Engineering Stack Exchange recommends it
Electronics Stack Exchange answerers point people to it when explaining why motors, relays and other coils need flyback diodes and what the voltage spikes look like without one.
Recommended by 5 people across 5 different months, 2011 to 2021.
What it is
A short explainer by Afrotechmods on inductive spiking, the voltage spike that appears when current through an inductor such as a motor or relay coil is suddenly cut off. It shows the effect on a scope and demonstrates how a flyback diode across the coil protects the circuit.
What people said
Strong rec Enric Blanco · 2017-03 · Electrical Engineering Stack Exchange · on “motor diode placement”
A flyback diode must be used this way: simulate this circuit [LINK] – Schematic created using CircuitLab [LINK] Otherwise, the collector voltage can overshoot well above the maximum rating of the transistor (and possibly destroy it) when the coil in the motor raises the voltage trying to compensate for its sudden current cut-off. Your circuit only protects the transistor against reverse current, but not from the overvoltage generated during cut-off. Take a look at this excellent video tutorial [this video] to see what happens with and without the flyback diode. Look at this snapshot from the video to see how big can the voltage spikes be: [LINK]
Recommends abdullah kahraman · 2011-12 · Electrical Engineering Stack Exchange · on “how to construct stepper motor driver?”
Controlling higher currents and voltages with the digital output is done using switches. Stepper motor driving is basically the same. It may change depending on your drive technique and stepper motor type, however it will be just your digital output to electronic switches that controls the windings. Go to here [LINK] and scroll down to "Using a transistor as a switch" to learn more about this. Also, this video [LINK] is a great tutorial. Don't forget the flyback (kickback, freewheeling) diode. Here [this video] is a video about that. Also it is important to know your stepper motor type. Driving techniques differ by stepper motor and winding type, however the electronic switch theory remains the s
Recommends JMaravalhasSilva · 2016-02 · Electrical Engineering Stack Exchange · on “Power Switch for 60V and 120A DC”
Something I would be cautious about is the inductive nature of any electric engine. Switching off a live circuit with inductive components will result in voltage spikes, and therefore electric arcs that can easily kill any switch and possibly even damage other components in the circuit. I recommend you watch this video [this video] for further information on that topic. Before trying to install a switch, I recommend trying to reverse engineer the power electronics in your scooter to make sure there are adequate protections against this, and if not, adding a flyback diode [LINK] to the engine should probably be enough to protect the circuit. I assume you are an EE student? It'll probably be a good
Recommends zeroskew · 2016-06 · Electrical Engineering Stack Exchange · on “How to connect flyback diodes on a h-bridge”
Add them in parallel to your motors, but in the reverse direction of the current flow. This allows the current still flowing through the motor (an inductor) to slowly dissipate back through the motor. This [this video] video gives a pretty good demonstration of the reasoning behind this.
Recommends Unknown123 · 2019-04 · Electrical Engineering Stack Exchange · on “Phototransistor relay circuit”
When light strikes Q1 (phototransistor), if the light is intense enough, Q1 is turned on, then current flows into the base of Q2 which also turns Q2 on, then what happens? Where is the current through the relay coil coming from The current in the relay coil is coming from VCC, because Q2 does turn on, and conducts that current to ground. – TimWescott how does the 2nd circuit work? The transistors on the first circuit is acting like normally open switch. So when there's no light shining on Q1 there will be no current through the base of Q2 and prevent the relay current to flow. Contrary to the first one, the transistors on the second circuit is acting like normally closed switch. When there i
Cites Mike Gleason jr Couturier · 2018-02 · Electrical Engineering Stack Exchange · on “Do I need a Schottky diode as a flyback diode with PWM @ 30 kHz?”
I use a regular diode ( 1N4007 ) as a flyback diode for a 250 mA 5 V fan. My transistor is a 2N 3904 and the PWM generator is an ATtiny85 : [LINK] I use this one because originally I was switching the PWM signal at low frequency ( < 1000 Hz ). I was able to ear a high pitch noise because the PWM signal was in the audible range. I decided to raise the PWM signal to 30 kHz . It seems to be working fine, I don't have a good scope to see the signal and most importantly, I can't hear the high pitch switching sound anymore. But after watching the video from afrotechmods ( [this video] ) he says that we need a Schottky diode when we are switching at > 1 kHz . Should I de-solder my diode and replace it w
Cites frr · 2018-04 · Electrical Engineering Stack Exchange · on “How to prevent a microcontroller to reboot due to Vcc fluctuations?”
I agree with Lucky Bot that PSU "holdover" is not a problem here, and I agree with Spehro Pefhany and Lucky Bot that this looks like an EMC problem. What happens when the pressure switch switches off is that an inductive load gets abruptly turned off. The "magnetic inertia" of the inductance tries to keep the current flowing, but you've barred the path by a very high resistance... which results in an immediate mighty voltage spike across the inductor's terminals, typically pulling an arc across the mechanical switch contacts, excited by the motor's winding. The arc itself is noisy, and the switch can be bouncey. Apart from the voltage spike, the brief but mighty dI/dT also produces an EM pul
Cites miksolo · 2021-10 · Electrical Engineering Stack Exchange · on “Controlling relays with logic gates”
To replace some simple logic such as CD4069UB with higher drive, you can use transistors. Such as MOSFETs or BJTs. Even the most basic transistors can give you power of 400 mW or more. This way, you can control the amount of output power you can drive by choosing a transistor (output current limited by open channel of transistor). If you drive relay when the output of inverter is high, you should take P channel inverter ( PMOS inverter on the picture). If you drive them low, you can use N side inverter. If however you need to have low output impedance on both LOW and HIGH output, use CMOS logic (P and N transistor). Here [LINK] are all representations of inverter with BJT or MOSFETs. To driv