Relay coil diode zener Mar 22, 2016 · In terms of relay coil voltage spike suppression, the following thread focuses on using a 1N4007 diode in series with a Zener across the relay coil: thread248-291225 But there are times when you need to suppress coil spikes but cannot put components across the relay coil. 5v - 0. 64W rather than 0. I have flyback diodes on every relay coil or commonly switched groups of relays. It suggests a diode and zener in series to be used for better contact life. When a Zener diode is connected in series with a diode type suppressor, the circuit will reduce the relay contact release time. Under normal operating voltage, the diode is reverse biased, so it doesn't conduct. What happens when you turn off the diode in a relay? In short, the diode takes that was recorded using an automotive ISO type relay with a 55 ohm coil and with 13. transistor) driving the relay has to withstand this Oct 20, 2021 · There was the technique of using a Zener diode in series with the classic freewheeling diode, and I am interested in knowing how to calculate the Zener voltage and power rating e. But just after the moment I press the button and energize the relay coil, the first line (no diode) shows a much bigger (in this case, roughly double) peak-to-peak voltage compared to the second line (with diode). 1V. This permits the relay to have optimum release dynamics and normally-open contact life. Sep 12, 2023 · In this article, we will explore the importance and usage of flyback diodes, covering their application in relays, solenoids, and DC motors. 9v / 80mA = 49 ohms After that the relay coil (with its diode) are connected between the PSU positive and the transistor collector. near optimum decay rate can be obtained by using a Zener diode in series with a general purpose diode. Dec 4, 2009 · For some high-end apps they use a zener across the relay coil, but in series with a diode and the zener is inversed to what is shown above. They certainly have sponsored products, as well as the Amazon prime, but I'm likely going with just a 3a multi pack, but I was just curious about the apparent popularity of the zener type. For the left it would just function a diode (with some supply clamping. Consult TE Relay Products Engineering for Current Rating: Ensure the diode can handle the maximum current that will flow through the inductor. Oct 15, 2022 · This results in the relay switching ON in sequence as desired by the application. 2 3. Created Date: 9/12/2022 2:09:54 PM. A flyback diode is also called as freewheeling diode. This near-universal practice is proof that the solution is practical and reliable. The larger the resistor, the better. When the relay turns the load off, fly back energy is shunted across the coil by the diode, thus eliminating extreme voltage potentials. When rapid opening of the contacts is important, a resistor or reverse-biased Zener diode can be placed in series with the diode to help dissipate the coil Jul 16, 2004 · relay coil snubber zener diode I assume you've already placed bypassing capacitors from VCC to GND as close as possible to the relay-coil and its driver? There are several factors that determine the effectiveness of the transient-suppressing diode, such as forward recovery characteristic, lead inductance and parasitic series inductances. It is also called by many other names like snubber diode, suppressor diode, catch diode or clamp diode, commutating diode. A zener can work in both but a diode wouldn't. The peak flyback voltage will be the resistor value multiplied by the relay coil operating current. A zener, as you have drawn it would go next to the mosfet. a diode is fast enough. It won't matter if the PSU is at 10v or 24v, the relay coil (when on) will always get 80mA. Thus the diode is placed backwards across the coil. Alternately, use just the zener but connect the anode to ground. A zener diode, however, can also be used for high voltage spike protection if connected ________. * The coil resistance were measured at a coil temperature of 23°C with tolerances of ± 15%. 9v emitter resistor = 3. Diodes inside relays without double Zener diode with double Zener diode To make it possible to connect the + at the –side and vice versa, and have surge protection: use a double Zener diode (= transil). Apr 10, 2015 · How do I calculate the resistor value needed in parallel with a relay coil to protect the switching transistor from the coil back EMF (I do not want to slow operation by using a flyback diode). WITH NO TRANSIENT PROTECTION: If the current in a relay coil is opened with contacts that have 1000 volt breakdown, then the energy in the relay coil is transferred to stray capacitance and the circuit From the standpoint of physics, the suggested technique for relay coil transient suppression is to use a reversed-biased rectifier diode and series zener diode in parallel with the relay coil. Despite this fact, the flyback diode is not an ideal solution. Jun 18, 2014 · The flyback diode is used on the coil of the relay, to protect whatever is driving it from being exposed to a high-voltage spike when the current through the coil is suddendly cut off. 2. 9 2. Does anybody know the value of it? If it is 1n4148, is it a Zener diode? What will be the biasing of it, whether it is wired to be forward biased for the relay coil or reverse biased and set to work in the breakdown region? If unfiltered half-wave or full-wave DC coil power is to be used, diode CR1 must be provided across the coil (and Z1 must not be used) so that energy will re-circulate to the coil and allow it to ride-through the low voltage portions of the power waveform without unseating the armature, buzzing, etc. Adding a simple catch diode will prevent any significant voltage from appearing on the solenoid or relay when it is released. The diode allows the current that was flowing through the driver to flow instead back through the coil itself, allowing the stored energy to be dissipated in the Apr 8, 2019 · Our Relay is rated at 24VDC (it is a Tyco Electronics 1432826-1). In my opinion the best compromise is a zener diode parallel to the driver. Aug 7, 2018 · The dual coil schematic would be clearer if you drew two coils. Feb 26, 2022 · However, a diode across the relay coil will keep the circulating current in a loop locally around the relay, instead of it having to go all the way back to the output driver, which would give some EMC advantages especially where the wires to the relay are long. (Refer to the following figure. You should ask that designer why (s)he wants to use a MOV while almost everyone else just uses a diode. Connect a diode in series with a Zener diode across the coil. diode is placed across the load. For example, if we use a 100Vdc SSR with a 48Vdc supply, then the voltage across the freewheel diode circuit must never exceed 52Vdc. Specify a diode for at least 79. We are basing the setup off of this picture. 3ms - transfer time 1. Flyback Diodes and Coil Suppression . In fact, manufacturers often integrate the diode into the relay socket or occasionally into the relay package itself. See full list on forum. Feb 14, 2024 · Counter electromotive voltage generated when the coil voltage of a relay is interrupted causes overvoltage to various elements in the circuit, resulting in malfunctions and breakdowns. For example, we have P-N junction diodes, light emitting diodes, and zener diodes. That way the current through the relay's coil decays faster. Oct 8, 2023 · Nor zener or schottky. Oct 13, 2020 · Diode +Zener diode type Snubber. It's purpose is to protect any solid state switching device (e. This is illustrated in Sep 5, 2009 · Mail order source for zener diode or suppressor? I went to town today looking for a bidirectional transient voltage suppressor as recommended or an 18 V or 24V 1 amp rated zener diode to put in series with a 1N4001 switching diode. Jul 8, 2019 · It's a 300V NPN transistor "MPSA42" driving the coil of a 12V relay (33 mA coil current) with no flyback protection whatsoever. 5 1. No zener diode or resistor should be in the recirculation loop because that reduces the ability to withstand the “off” time. Yes, relays can have diodes. 5v emitter = 4. In this case, a Nov 20, 2015 · I googled "zener in series with diode across coil" and came up with this circuit: - So, if the zener were shorted out what would happen when the transistor open circuits: The current that was formerly flowing into the BJT would flow through the diode and back to the top terminal of the coil. However, near optimum decay rate can be obtained by using a Zener diode in series with a general purpose diode. The diode will not see more than that. With repeated conduction, MOVs can eventually fail open. 4 mA current. Jun 21, 2015 · In the first design, you are limiting the induced voltage of the inductive relay to whatever the diode and zener diode are rated for. A zener. If the relay coil is fed with AC then maybe a MOV would be a solution but using AC to power a relay's coil is either rare or not allowed (for most relays as far as I Mar 2, 2010 · A relay that has a transorb across it's coil will have a higher voltage across the drive transistor than a relay with a diode across it's coil. As for diode voltage, look for 50V to 100V. ) The diode absorbs coil surge. I have also seen MOVs, TVSs and fast Zener diodes used in the configuration shown in Figure 1b. Of course this means that the driver (i. When the coil is energized, the flyback diode is reverse biased and does not affect relay operation. That's why wiring a diode in reverse bias (backwards) across the relay coil connections works to snuff out the spike. 1 9. Zener diodes are used to maintain a fixed voltage. A schematic for a relay's flyback diode circuit is shown below. In reality the kickback won't be infinite because the spike will trigger any sort of nasty effects in Feb 2, 2023 · One might note that relay life (in the relay datasheet) is typically specified without a diode across the coil. Speed: Choose a diode with a reverse recovery time that matches the switching speed of your circuit. This provided the fastest relay release possible while still allowing the flyback voltage to be "clipped" by the zener at whatever voltage is needed to ensure the Vce safety fo the switching device. 4 mA. 3) This arrangement gives the optimum protection of the drive circuit whilst ensuring the minimum effect upon the relay opening time (typically around +0. I probably should have replaced all 16 in the Hamplus when I first repaired it. Jan 23, 2024 · A relay being a relatively small load (high resistance coil), normally a 1 amp rated 1N4007 diode becomes more than sufficient for such applications, however in cases where the load is relatively huge or the coil resistance is very low, the generated back emfs could be equivalent to the applied current levels, meaning if the applied current is in the range of 10 amp, the reverse emf would also Suppression Technique Unsuppressed Diode & 24V Zener 680Ω Resistor 470Ω Resistor 330Ω Resistor 220Ω Resistor 100Ω Resistor 82Ω Resistor Diode 2 Drop-out Time (ms) 1. 6V x 130mA = 1. So I am looking for zener diode way. When the coil source is interrupted, the coil current is shunted through this series arrangement, maintaining a voltage equal to the Zener voltage (plus forward diode drop) until the coil energy is dissipated. Sep 10, 2021 · Using a Zener diode to prevent an LED from turning on until the power supply has fully ramped. You can clearly see that Why is there a diode connected in parallel to a relay coil? The purpose of a diode connected in parallel to a relay coil (flywheel diode or freewheeling diode) is to avoid damaging some nearby components sensitive to high voltage. 7V transient, and both the resistor-diode and the Zener-diode give about a 15V peak transient. A “recirculating diode” must always be used directly across the relay coil to allow the current to re-circulate and assist holding the relay in its operated state. So very simple and effective. The plot below shows this with a 5. 7 5. Why would you want a zener? You only want to redirect the back-EMF into the coil itself to prevent the spike. (Fig. ) For the right it will rapidly discharge the coil (if rated correctly - tvs) A diode. Although, I prefer the series zener diode combo across the relay coil instead: TVS diode should be redundant at this point (with the other two diodes), but it would go near the power supply/mosfet end, just in case something did get coupled into the long wires. I am using Panasonic ADW1212HLW relay. What zener diode (or regular diode if that would work better) would work best as a flywheel diode and why? Our Vin is also variable. g. But the diode is switched on when the circuit is opened and the EMF will be about 24. This causes the relay to generate more heat than in the recommended PWM circuit holding state because of the increased power consumption. Feb 6, 2017 · The signal diode blocks the zener when it [the zener] is forward-biased and would otherwise short the coil. In this schematic, the resistor R in parallel with the flyback diode wiring represents the coil's intrinsic DC resistance. May 21, 2021 · If you want the relay to turn off faster, you'll have to increase the voltage across it during turn-off, which you can do with an additional Zener diode in series with the flyback diode. Flyback diode wiring in a relay circuit Jul 2, 2014 · In some circuits its important that the release time of the relay or solenoid is not increased by the clamping, so a zener and diode combination is used. Relay Coils: Flyback diodes are commonly used across relay coils to prevent arcing across the relay contacts. In the second design, you are allowing the inductive relay to create a very large voltage spike when the switch is turned off. Oct 5, 2023 · The relay coil is for 44mA and 12V. This is the voltage needed in order for the relay to be able to operate and be able to open or close its switch in a circuit. No luck at the auto parts place or, surprisingly, Radio Shack (they had only 2 zener diodes, 12V and 5. Can I use 15V(Vz = 15V) zeners for D1 and D2 instead of 5. For the medium size contactor RC snubber became okay but for the bigger and other coil device it need tuning. The values of the resistors can be 10 ohms or 20 ohms depending on the resistance value of the relay coil. Coil current is 33 mA. The switching transistor is a 2N3904, Absolute max rating Vce of 40V. The flyback diode acts as a Jul 21, 2021 · Dear all, I am building a PLC system which control 24vdc relay and the relay finally control 220vac coil 380vac magnetic contactor. The diode connected across the relay coil is called a flyback diode or freewheeling diode. Then you not only don't have to worry about the supply voltage (because the diode is directly across the voltage-sensitive part i. In your relay, the coil current is shown as 79. Then there is no current through the resistor while the relay is operated. 5 6. I would put a large cap (1000 uF) in parallel with the zener, that will give good pull-in of the relay as while the cap is charging (at first turnon) there will be more voltage and current in the coil. 6V x 130mA = 78mW with a single diode. Specifically, many relays include a flyback diode, also known as a freewheeling diode, which is connected across the relay coil. Jan 4, 2017 · As explained in "Coil Suppression Can Reduce Relay Life," (2) this slow decay of current can create problems such as "sticking" between relay contacts. In many relays a zener diode is used for the clamping action to speed up the release time of the relay. Jul 9, 2012 · In this schematic, two zener diodes D1 and D2 are connected back-to back across relay coil L1. The relay is a SS-112D, coil resistance of 320Ω, 12V rated voltage, nowhere on the data sheet mentions coil inductance. 7V instead of just V_supply + 0. When used with a DC coil relay, a flyback diode can cause delayed drop-out of the contacts when power is removed, due to the continued circulation of current in the relay coil and diode. It will also, however, cause the coil to remain magnetized for much longer than it otherwise would. Data below. The inductance will cause the voltage to rise until D3 breaks down in reverse mode. 5ms for a standard automotive relay). Zener diodes can be distinguished from ordinary diodes by their code and breakdown voltage which are printed on them. 6v = 3. Jan 21, 2016 · The diode installed across a DC relay coil in what you'd view as a reverse biased fashion is called a free-wheeling diode (at least they used to be). It's a 2 coil latching relay with a coil voltage of 12 V. When SW2 opens current flows as shown in the equivalent circuit Figure 1d. Results showing a Zener diode fitted. Nov 21, 2008 · The 100 kohms plus the diode could as well be non-existing if you add a relay coil and connect it to an external DC source higher than the internal voltage (+5 V). The diode in parallel to the coil is usually there to limit the inductibe kickback voltage to protect the driver and here also the LED. For applications where the current must decay quicker, an alternative solution is to use a Zener diode as shown in Figure 4, which gives a faster current ramp rather than an exponential decay. The flyback diode, however, is not a type of diode but rather a diode application Therefore the longer term (after around 350ns) effect of the diode is negligible (if any). Commonly, this happens in scenarios where the release time of a diode is very slow. Feb 5, 2020 · In the past, I've used simple diodes for DC relays and MOVs for AC relays. For the right you have a dead transistor Apr 18, 2017 · In "Circuit 3" below, the external terminals of the relay coil are connected to a Zener diode + PN diode; this clamps the external voltage to 15V (above the 12V supply). The primary purpose of this diode is to protect sensitive components in the circuit from voltage spikes. A zener diode is normally used for voltage regulation. How the addition of a Zener diode to the ordinary diode can provide both voltage suppression and reliable switching performance. Otherwise the combined Aug 4, 2023 · Hello people, I need a bit of clarification regarding the below module, especially with the diode that is used. Usually a zener and diode clamp is less effective in reducing radiated EMF. D2 is forward biased and D3 is reverse biased. This is illustrated in I am following this application note for relay coil suppression. Jan 27, 2025 · Actually, a diode-Zener in series is the fastest. transistor) from the colapsing field of the coil when the transistor turns off to de-energize the relay. This is illustrated in Fig. The trade off, however, is that the switch will see V_supply + V_zener + 0. 6V and the initial dissipation will be 12. Jul 18, 2019 · Can a single Zener diode suppress a relay coil? In this case, a single Zener diode across the Collector and Emitter of a common-emitter BJT (which drives the low side of the relay coil), should be adequate to suppress the coil’s voltage spike to the Zener voltage. The cathode of the diode is connected to the + 5 V DC and the anode to the relay coil end that goes to the ground. Nov 2, 2023 · A single diode parallel to coil is the best protection to your relay driver but it also comes at the cost of the worst influence on relay lifespan. From a technical point of view, the best solution is a diode in series with a Zener diode and in parallel with the relay coil. 2ms The major difficulty comes from the capacitor volume. digikey. A simple diode can slow the opening of the contacts leading to arcing and premature wear. May 10, 2022 · A flyback diode in the relay circuit can be used to do just that. e. The most common coil suppression technique in relays is to connect a reverse-biased diode in parallel with the relay coil. This voltage is generated in the coil when the current flow is interrupted. In terms of relay coil voltage spike suppression, the following thread focuses on using a 1N4007 diode in series with a Zener across the relay coil: thread248-291225 But there are times when you need to suppress coil spikes but cannot put components across the relay coil. What is the optimum Zener diode voltage? When a Zener diode is connected in series with a diode as shown in the above figure, the large voltage drop of the Zener diode shortens the decay time of the coil current, which increases the opening speed of the relay contacts and prevents failure due to premature welding of the contacts. This type of suppressor is also not suitable for an AC circuit but good for a DC network. They are designed to 'breakdown' in a reliable and non-destructive way so that they can be used in reverse to maintain a fixed voltage across their terminals. The diode reverse voltage rating should be at least the voltage applied to the relay coil. Apr 24, 2023 · With the Zener diode bypassed, the time taken to discharge all the magnetic stored energy from the relay coil via the diode can be several ten of milli-seconds. For the non-latching case, you can speed up the switching off of the relay by connecting a Zener diode in anti-series with the freewheeling diode. com From a technical point of view, the best solution is a diode in series with a Zener diode and in parallel with the relay coil. Real-world Applications. Jun 6, 2013 · This can be avoided by inserting a diode is series with the resistor. May 15, 2023 · When relay coil is turned off, voltage is removed , relay coil generates voltage spike of opposite polarity , and only then the mentioned diode will conduct, and that spike is limited to roughly 1V . The operation time becomes: - time to start the movement 2. 8 Theoretical Transient -24. For the left it will be a normal chopper with a free wheel path. A double Zener diode prevents a surge generated by the relay coil and makes the relay polarity insensitive. Suggested Methods for Relay Coil Suppression From the standpoint of physics, the suggested technique for relay coil transient suppression is to use a reversed-biased rectifier diode and series zener diode in parallel with the relay coil. Connection of Diodes to the Operation Coil • Connect the standard diode and zener diode (or varistors) to the relay coil. Oct 8, 2023 · The same effect as a fixed resistor flyback suppression can be obtained by using a Zener diode, but across the driver transistor rather than across the coil. Regular Diodes, Zener Diodes and BJT transistors: is Zener diode-based voltage divider a good solution for gate driver supply? Zener control relay? Can I use a Zener for 556 protection from relay coil back EMF? Sep 8, 2017 · The placement of a flyback protection diode is rather simple; it should be placed directly across the relay's coil. May 23, 2015 · As you probably know, without any flyback diode, be it a rectifier or a Zener, you'll have a (theoretically infinite) kickback voltage from the inductor (valve coil, relay winding or whatever) whenever you try to interrupt its current abruptly. All the diodes are 1N4001 or 1N4007 so that they are better able to withstand lightning surges than the 1N4148. The relay Apr 27, 2009 · A diode can also be placed in series with a resistor to avoid the wasted power in the resistor, yet still largely improve contact release time over a diode alone across the coil. 3 2. The rating of the zener (current-wise) does not mean that the rated current (5. In your case, a 1N4001 current rating far exceeds the requirement. The record shown opposite is performed on the same relay as above. No diode, no zener diode, no resistor, no capacitor, nothing. If you need to suppress the back EMF of the relay coil, Sensata recommends the use of a zener-zener or diode-zener combination with the zener v oltage at 2 times, or more, of the coil source voltage. The back EMF will exceed the supply voltage by the zener voltage + the diode voltage. The diode acts like a short circuit with a small forward volt-drop and with the resistance of the relay (maybe 100 ohms), it will delay the relay de-activating Sep 26, 2023 · Well, when I go to Amazon and search "12v diode", I expect it to be their engine giving me the results 🤣. 7V, causing the inductor current to decay more quickly, switching devices more quickly. The reason it is slow is because when the circuit to the relay coil opens, all the energy stored in the relay coil forces a current thru the flywheel diode until that energy is "spent". The real situation with the open coil after the circuit has been opened is not that the voltage would become enormous anyway, if you measure it, you'll find "ringing" (a damped sinusoidal waveform) as the coil inductance resonates Nov 16, 2016 · It is also possible that the freewheeling diode can damage the relay. To fully protect the SSR, a zener diode placed across the Apr 27, 2009 · For some high-end apps they use a zener across the relay coil, but in series with a diode and the zener is inversed to what is shown above. 6 -20. Its main purpose is to protect other components from voltage spikes when the relay coil is de-energized. Jul 21, 2022 · That is the case for the Hamplus switch with its 16 diodes and 24 relays. In this case, a Apr 17, 2018 · The long and short of why you might want a zener in the first place is that the relay coil has quite a lot of inductance and when the relay coil is opened by turning off the drive transistor, the energy stored in the magnetic field has to go somewhere. In our example of a relay with a 290 Ω coil and time delay of 8 ms, a Feb 21, 2018 · Short answer: select a diode with a reverse voltage rating (often expressed as "peak inverse voltage", abbreviated "PIV") a bit higher than the power supply voltage and with a forward current rating greater than or equal to the relay coil operating current. 2 mA) flows in it. However, this diode will not pr otect the relay from transients generated from other sources. Thus countermeasures to suppress counter electromotive voltage are necessary. 5VDC applied to the coil. Nov 19, 2012 · If the relay just switches audio then you should be fine with any normal diode (1N4148 or 1N4004 etc) across the coil, release speed does not matter and most commercial audo equipment that uses relays in the signal path just uses a standard diode on the relay coil. Zener Diode Circuit for Over Voltage Protection Feb 14, 2024 · A typical PWM circuit & Zener diode combination requires a duty ratio of 86% or more to keep the coil current to maintain the relay on. This is called on a relay's datasheet its rated coil voltage. somethingV. Diodes are generally used for DC coils, but for some high-capacity relays a combination of a Zener diode as well as a diode is Apr 10, 2018 · a zener diode isn't going to be faster than a diode. This allows a higher flyback voltage and faster relay drop out without the power wastage incurred by the resistor in the on state. 8 -167 -115 -81 -54 -24. Schottky are meant for pretty low voltages, rarely over 100V. Although, of course the zener diode and 9V are incorrect. the transistor), but it also means the coil current isn't being dumped into your positive supply where it could end up affecting other circuit components. The diode make the relay a little slower to turn off. using a zener diode for coil suppression; the sum of the zener diode voltage, Vf of the freewheel diode, and DC supply voltage must not exceed the maximum voltage rating of the SSR. Dec 18, 2023 · Return to the Industrial Control and Automation Index Installing a flyback diode across the coil of a relay is a common practice. All relays come with a voltage rating. positive to cathode, ground to anode Sep 17, 2019 · A way to capitalize on this is to use a Zener diode back to back with the standard diode. . Nov 4, 2013 · Yes that should work ok provided the relay voltage and zener and supply voltages are all chosen correctly. 7 Volt using the figures from the above example. I measured this data using a 2N7000 MOSFET, and ICL-7555 chip, a 12V bench power supply, and this relay (12V coil, 16A contacts). In theory this should be better than a single diode because the coil voltage will increase to 12. During most of this period, the relay may stay energized enough to hold the contacts closed. I monitored the collector voltage with my least expensive {most expendable} oscilloscope. This will result in the back EMF generated being clamped to the forward voltage of the Zener diode and so controlling the amplitude but still aiding the faster collapse of the magnetic field. The BVds = -30V for Q1. 99% of the relays use a 1N4148 (Small signal relays) or 1N4007 (Beefier relays). Long answer: A relay coil is an inductor. 3 The specifications for all Sensata relays, unless otherwise specified, are without the use of coil suppression. So, I thought I'd give bidirectional TVS diodes a try on some 24VAC relays and contactors. Adding a zener diode in series (diodes with a precisely engineered breakdown voltage) increase the voltage drop across the inductor to V_zener + ~0. As for diode current, look for 50mA to 1A. Jul 9, 2016 · An improvement can be made by adding Zener diode D3 as shown in Figure 1c: D2 prevents forward current through D3 shorting out the relay coil. But the only Zener diodes. Application circuit looks like this: Z5, Z6 are 24 V zener diodes. Mar 1, 2022 · The purpose of a freewheel diode is to provide an alternative route for the coil current - if the current in the coil is forced to drop rapidly to zero it will fight back generating whatever voltage is necessary to keep that current flowing, which can be 100's or 1000's of volts. 1 V zeners? Will the relay coil or contacts can get damaged during turn-off of relay? If required, I'm using this relay (5V DC Standard Coil). 8 3. cause the coil holding voltage to fall below this level. 1 -0. This is the current that will flow through the diode when the coil is switched off. We Jul 18, 2024 · The relay may include an additional diode anti parallel to the LED - than one may get away without the extra external diodes. Second. These spikes occur when the relay coil is de-energized and the magnetic field There are many types of diodes. 1V zener diode in series with a conventional signal diode as a clamp, limiting the coil back-EMF to around 6. So with 12v supply to relay transistor is getting close to 13v spike. These appear to have disadvantages. This allows the current in the inductor to dissipate at a stable rate through itself. 7V. In this case, a To drive a DC relay, all we need is sufficient DC voltage which the relay is rated for and a zener diode. 8 Suggested Methods for Relay Coil Suppression From the standpoint of Jun 20, 2013 · That acts as a constant current relay driver; base = 4. Below is an LTspice sim for a 1H, 120Ω inductor for three voltage suppression configurations: a diode, a 130Ω resistor-diode, and a 12V Zener-diode: The diode give about a -0. capacitor inrush current in the case of a low resistance coil. for a 24 VDC/400 mW relay coil. The app note “Coil Suppression Can Reduce Relay Life” from TE says that a diode and zener in series work better than the diode alone. lnrfhmgzaepcszkuhqwenkdteydfnhjrxhqhtjouugznqosqgxwhozhslitxxeeupcnjzti