Dealing with mains power transients

Started by Sylvia Else in sci.electronics.design4 years ago 19 replies

I'm looking at protecting a power sense circuit from mains power transients, using a resistor and a zener diode. Spice says it works well,...

I'm looking at protecting a power sense circuit from mains power transients, using a resistor and a zener diode. Spice says it works well, but when the zener conducts, essentially the entire transient voltage appears across the resistor. A high voltage transient spike is likely to be very narrow, but I can find nothing to say I can put, say, 5000V, across a 1K resistor, even for a micro...


Zener voltage limiter without voltage drop to the load

Started by Anonymous in sci.electronics.design8 years ago 47 replies

Schematic at link below. https://picasaweb.google.com/bhavanireddy/Temp#5763185160849573218 Input voltage varies from 8-18V. The voltage to...

Schematic at link below. https://picasaweb.google.com/bhavanireddy/Temp#5763185160849573218 Input voltage varies from 8-18V. The voltage to relay shouldn't drop as long as it is less than 12V and remain at 12V when the input voltage raises above 12V. Will the above circuit do the job? All the Zener voltage limiters I see have current limiting resistor in between the input and load befor...


7809 vs 9.1v zener?

Started by Father Haskell in sci.electronics.design8 years ago 7 replies

Low current ( < 100 mA) power supply regulator. Any reason I'd want to use 7809s instead of cheaper 9.1v zeners?

Low current ( < 100 mA) power supply regulator. Any reason I'd want to use 7809s instead of cheaper 9.1v zeners?


Combating Zener Jitter

Started by Chris in sci.electronics.design3 years ago 44 replies

Has anyone got any suggestions as to how to best deal with the phenomenon of jittering zeners? Preferably without adding excessive complexity to...

Has anyone got any suggestions as to how to best deal with the phenomenon of jittering zeners? Preferably without adding excessive complexity to a circuit, I mean.


MOSFET gate protection

Started by circuitmaker in sci.electronics.design3 years ago 4 replies

I have an AC 230V relay built of discrete MOSFETs. Would a 12V 0.3W Zener diode in SOD323 coupled directly to the gates/sources be an...

I have an AC 230V relay built of discrete MOSFETs. Would a 12V 0.3W Zener diode in SOD323 coupled directly to the gates/sources be an appropriate protection against spurious turn-ons/oxide puncture due to high dV/dt on DS or do I need a TVS? c.


Best Way To Power This ?

Started by Anonymous in sci.electronics.design1 year ago 6 replies

I got these two pieces of equipment. One is a Data Precision benchtop DMM. It had a bad power transformer. It runs on a shunt Zener regulation...

I got these two pieces of equipment. One is a Data Precision benchtop DMM. It had a bad power transformer. It runs on a shunt Zener regulation using the impedance of the transformers. not something I would have done. But it's current drain is in the mA, maybe 100 or so. Might be a bit more if I happen to be reading 88.888 volts, it is LED. I prefer that, I find it easier to see a


Zener SOAR

Started by John Larkin in sci.electronics.design3 years ago 21 replies

Well, there don't seem to be SOAR specs on zeners. I suppose I'll have to blow some up. -- John Larkin Highland Technology,...

Well, there don't seem to be SOAR specs on zeners. I suppose I'll have to blow some up. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com


Zener Q

Started by Robert Baer in sci.electronics.design8 years ago 33 replies

Which voltage has the lowest average temperature coefficient (say 20C to +40C): 4.7V or 5.1V? "Average" is to mean a sample of 150 from...

Which voltage has the lowest average temperature coefficient (say 20C to +40C): 4.7V or 5.1V? "Average" is to mean a sample of 150 from hundreds of thousands. Is there a variation of the average TC between parts from wafer to wafer, and how much? Ref: Vishay MMBZ230, MMBZ5231.


Again with an oops.

Started by George Herold in sci.electronics.design2 years ago 14 replies

I semi-disabled the output of my opa2134 today. Output had right sign at rail, but not enough current. Crappy ascii. |\ ...

I semi-disabled the output of my opa2134 today. Output had right sign at rail, but not enough current. Crappy ascii. |\ v-ref--|-\ don't zener base, diode | > --R_5k--+--| | (pnp 450V) |--gnd Gnd /| | |


Why are IGBT's used in ignitions so much?

Started by Joerg in sci.electronics.design2 years ago 42 replies

Considering the typical saturation voltages of > 1V it doesn't look attractive yet they are...

Considering the typical saturation voltages of > 1V it doesn't look attractive yet they are popular: https://www.fairchildsemi.com/datasheets/FG/FGD3040G2_F085.pdf Why? There are plenty of cheap MOSFETs that are in the low tens of milliohms and thus show only a fraction of the losses while the coil current ramps up. You'd just have to add a zener from drain to gate in case the spark


79L05 stability, output capacitance

Started by Joerg in sci.electronics.design5 years ago 49 replies

Folks, Normally I never use them but today I need a couple of small negative regulators, one of them with an upfront 3-4V zener to burn off...

Folks, Normally I never use them but today I need a couple of small negative regulators, one of them with an upfront 3-4V zener to burn off some power outside its package. LM79L05 in SOT89. Older datasheets prescribe tantalums (not going to happen here) and newer ones don't mention anything other than "0.1uF" or they mention simply nothing. I want to use ceramci caps and the grand tot...


PNPs with high BV_EBO

Started by Phil Hobbs in sci.electronics.design2 years ago 44 replies

I'm doing a Class G driver for a thermoelectric cooler. (I don't want to use Class D because of the switching trash--with Class G it's a lot...

I'm doing a Class G driver for a thermoelectric cooler. (I don't want to use Class D because of the switching trash--with Class G it's a lot easier to get good filtering in a small space.) One issue is that the power supply on the Class G will be only a few volts, and the control electronics is running on +12, so it's easy to zener the BE junctions of various transistors. The 2SD270...


Zenering a big transistor

Started by George Herold in sci.electronics.design3 years ago 57 replies

I'm using a TIP31C (pnp in to-220 pac) as a temp sensor (diode connected) There's a couple of depletion fets in series as current limiters....

I'm using a TIP31C (pnp in to-220 pac) as a temp sensor (diode connected) There's a couple of depletion fets in series as current limiters. (LND150) The b-e junction starts to zener at ~30 V (only two tested so far). So I've got ~1.5 mA flowing at 30 V. Is this going to damage the junction? Will it take time? I'm going to measure forward voltage again after zenering for 15 minutes. Sho...


Simple ad hoc design continues to be useful

Started by Pimpom in sci.electronics.design5 months ago 13 replies

Have you ever designed and built something ad hoc (usually a simple one) but later found it useful for other applications? I have a few of...

Have you ever designed and built something ad hoc (usually a simple one) but later found it useful for other applications? I have a few of those. For example, I made an adjustable constant current source in the late '80s, specifically for sorting out my old collection of zener diodes. It supplies a regulated current that can be adjusted from 0.5 to 15mA at up to 50V. I fully expected ...


Radiation effects on 2n2222 or similar

Started by Robert Baer in sci.electronics.design1 year ago 19 replies

Placing the working unit (open base) in a very high dose area for 2 months, where it will see approximately a rate of approximately 15...

Placing the working unit (open base) in a very high dose area for 2 months, where it will see approximately a rate of approximately 15 Rem/hour. Not steady state, but plenty every day. In the Apollo daze, some data may have been collected concerning this question (uA709 W-stepping, input pair). Is there any data concerning E-B zener voltage changes, and is there any materi...


Zener noise / oscillations

Started by Robert Baer in sci.electronics.design8 years ago 145 replies

Zeners all seem to behave: quiet, no oscillation IF run at or near the spec current (usually in the tens of mA). But, if one needs to run...

Zeners all seem to behave: quiet, no oscillation IF run at or near the spec current (usually in the tens of mA). But, if one needs to run them at low currents (say 10uA to 500uA) then _watch_out_! Some brands at certain voltages are extremely noisy and subject to oscillation. The waveforms seen at low currents (2-50uA) look like randumb sawtooth generation, and as the curren...


More methods to salvage leakage energy in a flyback?

Started by Joerg in sci.electronics.design6 years ago 58 replies

Folks, Have to do a flyback-PFC but this time with a really good efficiency, > 90%. The output voltage is high enough that sync...

Folks, Have to do a flyback-PFC but this time with a really good efficiency, > 90%. The output voltage is high enough that sync rectification isn't needed. AFAICT the only other way to boost efficiency is to not flare off the leakage inductance spike via zener or snubber but to recycle it instead. Unfortunately a recuperating winding only works if the duty cycle stays under 50% at all


Transformerless power supply

Started by mkr5000 in sci.electronics.design8 years ago 20 replies

I have a simple circuit on a breadboard that has been doing fine 24/7 for months which is -- 120vac, hot into a 200k 1/2 watt that feeds a...

I have a simple circuit on a breadboard that has been doing fine 24/7 for months which is -- 120vac, hot into a 200k 1/2 watt that feeds a dropping cap (.47uf, 400v) that then feeds a bridge rectifier. The output of the bridge has a zener and a filter cap which supplies my DC. I breadboarded it because I really never used a transformerless design in a project and just wanted to see how relia...


Zener Vs PN diode difference in forward mode

Started by Clive Arthur in sci.electronics.design3 years ago 47 replies

Apologies for the on-topic post. I have a class B amplifier with complementary Darlingtons for output, and an op-amp driving the...

Apologies for the on-topic post. I have a class B amplifier with complementary Darlingtons for output, and an op-amp driving the tied-together bases with -ve feedback from the output. It's simple and works pretty well. I was tinkering with LTspice to reduce the crossover distortion. I don't want class AB quiescent current, but putting three diodes between the bases to make the volta...


Turn signal flasher question

Started by amdx in sci.electronics.design3 months ago 8 replies

I have a turn signal flasher that I no longer hear. After both my kids commenting on my turn signal being on, I decided to do something about...

I have a turn signal flasher that I no longer hear. After both my kids commenting on my turn signal being on, I decided to do something about it. I tried just adding a mechanical piece to make it louder, it did but probably not enough. So I found a Sonolert and wired it to the output. However the output of the Flasher sets at 6V. I don't know why. I just put a zener in series and that...