hybridfree/eevblog-posts huggingface dataset:
fluke TPWS - Page 1
Forum section: electronics / beginners

author: M0BSW
author_rank: Frequent Contributor
timestamp: October 21, 2012, 06:46:21 pm
content: A simple question what is a fluke TPWS, is it a special type of multimeter ?

author: Monkeh
author_rank: Super Contributor
timestamp: October 21, 2012, 06:54:42 pm
content: http://www.rail-reg.gov.uk/server/show/nav.1559It's nothing more than a Fluke 287 which has been tested and approved for use on these systems.

author: M0BSW
author_rank: Frequent Contributor
timestamp: October 21, 2012, 07:02:26 pm
content: Quote from: Monkeh on October 21, 2012, 06:54:42 pmSo it would be fine on hobby electronics, I found out it was used on railway engineering.

author: Monkeh
author_rank: Super Contributor
timestamp: October 21, 2012, 07:05:56 pm
content: Quote from: M0BSW on October 21, 2012, 07:02:26 pmYes, it's just a multimeter.A little more digging shows Fluke 115, 117, 179, and 87V models are also available as TPWS approved, and there's one on ebay (I assume the one you're looking at) which looks like a 187. They're nothing special, just red tape.E: And clamp meters, IR thermometers, thermal imaging cameras, insulation testers, and power analyzers. Fluke are making a pretty penny here.

author: M0BSW
author_rank: Frequent Contributor
timestamp: October 21, 2012, 07:33:48 pm
content: Quote from: Monkeh on October 21, 2012, 07:05:56 pmYes it is the TPWS had put me off really, could do with another good meter.
Fluke type meter connectors? - Page 1
Forum section: electronics / beginners

author: Crambone
author_rank: Frequent Contributor
timestamp: November 16, 2022, 10:03:53 pm
content: I have a meter that has the old banana plug on the front and want to change it to the normal fluke type meter jack but not sure where to find them?

author: BillyO
author_rank: Super Contributor
timestamp: November 17, 2022, 12:33:05 am
content: I could be wrong, but I don't think that would be possible without some major re-building. It might be cheaper to buy a Fluke.

author: bdunham7
author_rank: Super Contributor
timestamp: November 17, 2022, 12:49:02 am
content: Quote from: Crambone on November 16, 2022, 10:03:53 pmJust so we're sure what you mean, can you define those two terms or show photos or state examples? Believe it or not I'm not being pedantic as I can think of multiple examples for either description. And what meter (make/model) do you have that you want to modify?

author: Jwillis
author_rank: Super Contributor
timestamp: November 19, 2022, 12:42:16 am
content: Quote from: Crambone on November 16, 2022, 10:03:53 pmShrouded or Safety shrouded 4mm banana plug/socket . Avoid the cheap ones because the plastic seems brittle and ware out faster. Staubi , Pomona , Tenma are good bets.https://my.rs-online.com/web/p/banana-connectors/2263051
fluorescent tubes and ambient temperature - Page 1
Forum section: electronics / beginners

author: hl68fx
author_rank: Newbie
timestamp: January 30, 2020, 12:37:49 am
content: Hi everyone,I would like to use fluorescent tubes in some kind of furnace. Can you tell me what happens to these lamps being used in an ambient temperature of 80 to 100 °C?What happens to light output and lifespan? Will it be possible at all?Kind regardsTom

author: Jwillis
author_rank: Super Contributor
timestamp: January 30, 2020, 01:20:22 am
content: Fluorescent tubes are very sensitive to ambient temperatures .Light output drops off significantly either direction of 25 to 30 degrees centigrade. For example exterior lamps go very dim at -20C and again grow dim in very hot areas.Different Types can be effected differently by ambient temperature.http://www.lamptech.co.uk/Documents/FL%20Temperature.htmandhttp://www.lamptech.co.uk/Documents/Journals/Thorn%20Lighting%20Journal%203.pdfdo a better job of explaining this.

author: amyk
author_rank: Super Contributor
timestamp: January 31, 2020, 02:32:03 am
content: I recommend using incandescent if you need it to withstand high temperatures --- lightbulbs are much hotter than that inside.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: January 31, 2020, 02:58:30 am
content: Another choice is to use a light pipe to bring light in from whatever source floats your boat. Glass fibers and pipes will easily handle the temperatures you mention.
Flux conductivity - Page 1
Forum section: electronics / beginners

author: alecto
author_rank: Contributor
timestamp: May 10, 2015, 10:39:28 am
content: I'm a Beginner with a capital B...I'm getting better at soldering...and I try to do what is supposed to be done....I use 0.38mm multicore solder(60/40), a temperature adjustable soldering station with chisel tip(2.4mm or 3.2mm depending on what I'm soldering)....and some cheap flux that contains zinc chloride.Recently I had problems with little projects...on the breadboard everything was fine... then I soldered those....and today, again... little project... breadboard ok...but once soldered...troubles!!so I begin to check:-if I made a connection mistake....nope(really easy project)-checked for bridges with a magnifier(8x with led ring)...no bridges...again with my DMM continuity tests...no buzz but a little resistance(60~80) between two pins where it shouldn't??? so back to the magnifier and again no bridge but some flux residue...So I scrapped the flux residue(last hope before desoldering stuff...)and BOOM everything was fine....can flux residue be conductive??or the flux I use?

author: Rerouter
author_rank: Super Contributor
timestamp: May 10, 2015, 10:44:08 am
content: yes, and depending on what had deposited on the board surface before hand it can be on the same roder as what you saw there,There are different types of fluxes, but even if you use a non conductive one, the metals and oils that deposit out of the air over time, once it has a medium to move around in like molten flux tend to concentrate in, can cause exactly what you are seeing, and is part of why cleaning off the flux is a good habit to follow,

author: wraper
author_rank: Unknown
timestamp: May 10, 2015, 11:08:38 am
content: Zinc chloride flux is completely unsuitable for electronics and destroys soldering iron tips too.

author: wraper
author_rank: Unknown
timestamp: May 10, 2015, 11:10:33 am
content: Quote

author: alecto
author_rank: Contributor
timestamp: May 10, 2015, 11:39:57 am
content: first thanx for the fast replies...so buying the only flux I found at my local hardware store ...bad Idea...ok lesson learned...Quotethanx for that tip too(pun intended)I couldn't keep their efficiency over time, but now I know why....and also I just realized I should have search ggogle whith the terms "Zinc chloride flux"...so obvious...
Flux pen toxicity and Conductivity - Page 1
Forum section: electronics / beginners

author: 128ITSH
author_rank: Contributor
timestamp: January 20, 2019, 04:23:41 pm
content: Hello,Recently I started doing some SMD soldering, so I bought aCW8100 No clean flux pen.The thing came with lots of warning about the affects it has. All are inthis MSDS.For more background i'll say that I solder in my bedroom, while my door and a 1meterx1meter window are open, and the soldering station is 1 meter from the window, with a 12V DC fan sucking the fumes to the direction of the window (not necessarily making them go out of the room, just away from me).I would be happy if someone who knows about would check the MSDS and tell me what I should and should not do. I am able to set up a more advanced air cleaning system if that is needed.My other question is weather should I clean this flux after use in some way? Is it conductive? what about high voltage (230V AC mains)?

author: amyk
author_rank: Super Contributor
timestamp: January 20, 2019, 06:45:27 pm
content: Don't forget that MSDS are almost always going to overexaggerate risk, for reasons of legal liability. You can look up the ingredients separately and assess for yourself:- propan-2-ol: this is regular isopropyl alcohol, biggest concern is flammability.- adipic acid:https://en.wikipedia.org/wiki/Adipic_acidmildly toxic and irritating, like any acid (but has a higher LD50 than sodium chloride)- dimethyl glutarate:https://echa.europa.eu/documents/10162/13eda1a8-4f68-4b6e-8559-9bb66c1018bcshows that it is relatively safe- rosin: you should know what this is

author: 128ITSH
author_rank: Contributor
timestamp: January 20, 2019, 07:53:22 pm
content: Quote from: amyk on January 20, 2019, 06:45:27 pmI can conclude from this that I should just use gloves and have proper ventilation. I'm wearing glasses normally so I don't need extra eye protection (or do I?).
flux-shunt transformer - Page 1
Forum section: electronics / beginners

author: Sblanc
author_rank: Newbie
timestamp: June 13, 2022, 02:37:05 am
content: Hi there,I'm studying to get my electrical licence and on the website the school give as to study there is a picture of this flux-shunt transformer but not more information about.Anyone knows anything about this type of transformer?Thanks.

author: coppercone2
author_rank: Super Contributor
timestamp: June 13, 2022, 04:10:07 am
content: A flux shunt means that there is a magnetic element to allow the magnetic force to pass through the shunt rather then through the other core. So if you have a doughnut core with windings on both sides and you put a steel plate in the middle that fits nicely it will be a magnetic shunt (so it turns it into a 8 ), its like putting a resistor across a light bulb in parallel to drop the light outputit holds to the law of parallel resistors but with magnetic force rather then electric currentas you can imagine putting something to change the series magnetic path resistance of the device is difficult with a fixed core made out of glue and steel but you can always jam something into the hole with little effort to change the magnetic force going through the winding.

author: Zero999
author_rank: Super Contributor
timestamp: June 13, 2022, 08:25:02 am
content: It increases the leakage inductance, therefore the impedance, to limit the current.

author: jonpaul
author_rank: Super Contributor
timestamp: June 13, 2022, 09:53:58 am
content: Bonjour, where are you located? Any link to the website with this image?The image is a variable shunt neon sign transformer to create a variable current at high voltage for testing or bombarding neon gas tubes.In general shunted transformers are used to limit short circuit current, in arc lamps, neon signs, and microwave ovens.Special laminations are used in production with a fixed shunt built in, or a separate lamination bar is inserted after winding after the other laminations are assembled.As the lighting industry migrates from ancient arc lamps and gas tubes to modem LEDS these are used less and less.microwave ovens also have evolved from a HV shunt mains transformer and diode to a modern SMPS inverter.Thus these are more of historical interest, but still a very fine magnetic circuit example.Bon chance,Jon

author: Uunoctium
author_rank: Frequent Contributor
timestamp: June 13, 2022, 10:15:45 am
content: may be from here:https://electricalacademia.com/transformer/special-transformers-applications/( bottom, last picture )And don't believe what they wrote about it!THIS IS NOT A WELDING TRANSFORMER!Connecting welding cables to it qualifies for 1st prize at the Darwin Award
Fly back diode - Page 1
Forum section: electronics / beginners

author: SolidFloyd
author_rank: Contributor
timestamp: May 23, 2011, 09:57:23 am
content: Hi, I'm doing a project using some pneumatic valves that are controlled by selonoids, the selonoids are activated by some digital signals from a robotcontroller. All outputs are optically isolated outputs. The manual to the robotcontroller states the following:QuoteSo I need some sort of fly back diode to protect the controller, right?The cables to the valves got some electronics in them, does this act like a fly back diode? or do I need to add some diodes. Please se picture below. Tnx

author: Psi
author_rank: Super Contributor
timestamp: May 23, 2011, 10:14:12 am
content: Are you going to be driving the solenoid(s) with both polarities?That circuit looks to be designed so it will snub flyback for both polarities using two diodes. The forward voltage of one and the breakdown of the other (which swaps around when the polarity is reversed)When you need to use both polarities like that things are a little more complex as you can't just snub any reverse voltage with a single diode that's forward biased for any flyback voltage. You need to spec the diodes for breakdown as well.If you just want to drive a solenoid on/off (no reverse polarity) you can put a general purpose power diode across it, eg 1n4007 for a small solenoid or a larger general purpose diode if it's a big solenoid. Of course, there are diodes specially designed for the task if you want it to be a bit more robust/professional.(incase you don't know what i mean my driving a solenoid with reverse polarity.. Some solenoids have two coils so you can invert the power and drive them back to rest position faster, instead of relying on a spring)

author: SolidFloyd
author_rank: Contributor
timestamp: May 23, 2011, 10:33:35 am
content: Hi, tnx for replying..I'm only going to turn the solenoids on and off, no reverse polarity. Then I just put a diode across the solenoids...tnx

author: tecman
author_rank: Frequent Contributor
timestamp: May 23, 2011, 03:40:37 pm
content: I am very familiar with the type of suppression you indicated. We use them on solenoid vales all the time. The back-back zeners shown make it polarity insensitive, in other words you can wire it without paying attention to polarity. Using zeners will also make the drop out time of the valve faster and more consistent than just with a simple diode. Of course, it costs more. If you are doing induatrial wiring, the suppressor shown is a cheap, simple solution. If you are DIY, a 1n4004 or similar just wired across the coil, with attention to polarity work normally work just as well.paul
flyback calculation - Page 1
Forum section: electronics / beginners

author: sk614
author_rank: Contributor
timestamp: June 23, 2017, 06:21:58 pm
content: Hi I want design a multiple outputs flyback converter with outputs as following.Vo1=5@2AVo2=12@1AVo3=24@.5ATotal 34W.My question is when I start calculating do I calculate for each individual output or can I use the maximum output voltage (24@ 1.41A) for my calculation? Does my question make sense?

author: Benta
author_rank: Super Contributor
timestamp: June 23, 2017, 07:07:51 pm
content: For primary and core calculations, just use the total output power in some form, eg, like modelling it with one secondary such as your 24 V @ 1.41 A.How the secondary voltages are split is unimportant, and can even be changed along the way.In the end, you'll need some sensible turns ratios, of course.

author: sk614
author_rank: Contributor
timestamp: June 23, 2017, 07:19:32 pm
content: Thanks for the input. So after getting the primary side calculations I can then use each outputs separately (Vo1, Vo2, Vo3) to calculate each secondary parameters? i.e. I1_peak,I2_peak, I3_peak..etc

author: Benta
author_rank: Super Contributor
timestamp: June 24, 2017, 09:00:29 am
content: You' have to define which one of your outputs is the "master" from where you do the feedback. Calculate that one, the other two will be given automatically from the turns ratios. Same with wire gauge, this will be apparent from the wanted output current.You probably won't be able to get a perfect relationship between 5 V and 12/24 V, as "fractional" windings normally aren't possible.
Flyback diode 2 in series  - Page 1
Forum section: electronics / beginners

author: rakeshm55
author_rank: Regular Contributor
timestamp: March 22, 2017, 04:42:47 pm
content: Hi..I have a fan cntrl design where in I need to place a flyback diode across a 48V brushless type fan 19W .... I want to use smd type diode....i already have Schottky key type diode 40V max reverse voltage in stock....Can I place 2 of such diode in series as flyback (40+40)...Will such design be sturdy ??. Or do I need to choose diode with higher reverse voltage.....I was trying to avoid procurement of new parts .....pls advice

author: Zero999
author_rank: Super Contributor
timestamp: March 22, 2017, 05:35:48 pm
content: Please don't double post.https://www.eevblog.com/forum/beginners/flyback-diode-for-motor-brushless/
Flyback diode for a constantly-powered fan - Page 1
Forum section: electronics / beginners

author: amaningd
author_rank: Contributor
timestamp: July 25, 2022, 09:24:03 pm
content: I'd like to power a fan with a PCB I'm designing that has a +12V supply rail. I'm thinking of simply placing the fan across the supply/ground rails since I don't need PWM or any finer control for my particular application. I know that when I switch off an inductive load using a transistor, I need a reverse-biased flyback diode to suppress the induced voltage spike; but is a flyback diode from GND to +12V still necessary for when the PCB is disconnected from power?

author: RoGeorge
author_rank: Super Contributor
timestamp: July 25, 2022, 09:36:31 pm
content: Quote from: amaningd on July 25, 2022, 09:24:03 pmNo external diode is needed for 12V computer fans.Those fans have an integrated circuit inside that drives the coils, and any flyback diodes, if necessary, are already included in the fan's electronic (it's a brushless motor, has a small PCB with electronics inside).

author: MrAl
author_rank: Super Contributor
timestamp: July 26, 2022, 02:47:33 pm
content: Quote from: amaningd on July 25, 2022, 09:24:03 pmHi,Depends highly on the type of fan and the type of power supply.Some fans can even generate a voltage with the same polarity as the power supply output meaning a 'back emf' diode wont even do anything. You would need a zener unless you can use a diode to bypass the power supply itself (a diode from output to input instead of in reverse from output to ground).You might do some tests. Measure the voltage across the fan when powered from a battery then disconnect the battery and see what the voltage across the fan does. If it does negative you may need a reverse diode, if it goes positive you may need a diode from output to input of the power supply or a zener. There's a chance you dont need any diode if the power supply can take it.
Flyback diode for motor brushless - Page 1
Forum section: electronics / beginners

author: rakeshm55
author_rank: Regular Contributor
timestamp: March 22, 2017, 04:41:23 pm
content: Hi..I have a fan cntrl design where in I need to place a flyback diode across a 48V brushless type fan 19W .... I want to use smd type diode....i already have Schottky key type diode 40V max reverse voltage in stock....Can I place 2 of such diode in series as flyback (40+40)...Will such design be sturdy ??. Or do I need to choose diode with higher reverse voltage.....I was trying to avoid procurement of new parts .....pls advice

author: james_s
author_rank: Super Contributor
timestamp: March 22, 2017, 04:54:55 pm
content: Is this for a one-off hobby project or a commercial design?Generally you can get away with putting two matched diodes in series. It isn't always a good idea but it will probably be fine.

author: rakeshm55
author_rank: Regular Contributor
timestamp: March 22, 2017, 05:42:13 pm
content: This is for an industrial design....Since I was already using a similar part in other section of design I thought of using the same diode......If putting them in series is not a recommended practice then I would use an appropriate part......

author: Zero999
author_rank: Super Contributor
timestamp: March 22, 2017, 05:42:13 pm
content: The usual reason for doing this is to increase the reverse blocking voltage but it doubles the forward voltage and it can be problematic ensuring the reverse voltage is shared between each diode. In this case it's not a good idea and is completely unnecessary, as silicon and Schottky diodes with a higher reverse blocking voltage than 48V are widely available and aren't expensive.If this is just a quick prototype and you're on a tight timescale. Order the correct components, then use two 40V diodes in series, just to get it working, whilst you're waiting for your order and replace them with the correct diodes, as soon as they arrive.

author: MagicSmoker
author_rank: Super Contributor
timestamp: March 22, 2017, 08:29:00 pm
content: Wait just a second here... why do you need a flyback diode for a brushless fan? Brushless fans are essentially tiny AC motors with an integrated inverter, so you don't need an external flyback diode because they are already present across each switch in the inverter.edit: grammar

author: james_s
author_rank: Super Contributor
timestamp: March 22, 2017, 09:44:13 pm
content: That's a good point. I had assumed the OP was designing an inverter to drive a brushless fan motor rather than a self contained brushless fan but now that I read it again I'm not sure.

author: rakeshm55
author_rank: Regular Contributor
timestamp: March 23, 2017, 03:43:31 am
content: Great!! Thank you for your suggestion .... So I may not need flyback protection for a brushless fan ..... i am attaching my choice of fan and pwm controller ICFan spechttp://www.ebmpapst.com/en/products/product_search/productdetailaxialcompact.php?pID=53812PWM controllerhttp://ww1.microchip.com/downloads/en/DeviceDoc/21755C.pdf
Flyback diode for reversing 12V 3A DC motor - Page 1
Forum section: electronics / beginners

author: SlowBro
author_rank: Regular Contributor
timestamp: September 25, 2019, 03:29:44 am
content: What specs ought I be looking for, for a flyback diode on a 12V 3A DC linear actuator? (I don't know the RPM.) It's reversed using a pair of SPDT relays. I'm thinking a bidirectional zener but no clue how many volts/current/etc. I'm aiming to protect the relay points.

author: Zero999
author_rank: Super Contributor
timestamp: September 25, 2019, 08:03:32 am
content: If you have access to the 12V supply, then a bridge rectifier will do. Connect the negative to +12V, the positive to 0V and the AC part across the actuator.Failing that, two 18V zener diodes connected back-to-back, in parallel with the actuator, will do. They don't have to dissipate the full power continuously so something like 3W will probably do.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 25, 2019, 08:07:54 am
content: Or a bidirectional TVS, like a P6KE18CA or SMAJ18CA.Don't forget the DC input side of the relay needs to be well bypassed also; if it's supplied by long wires, you will get some flyback from that direction as well. A local TVS or capacitor there may be desirable then.Tim
Flyback diode on a transformer primary? - Page 1
Forum section: electronics / beginners

author: nsled
author_rank: Contributor
timestamp: May 01, 2024, 04:25:32 pm
content: A transformer primary is driven with a pulsed DC square wave source. Can I use a diode to prevent any EMF from returning to the driving circuit? Should it just be placed in series with the positive line input or in parallel with the coil?Is there any negative effect to doing this?

author: xvr
author_rank: Frequent Contributor
timestamp: May 02, 2024, 07:42:12 pm
content: In flyback topology all energy from primary side transferred to secondary, so no EMF on primary side (in ideal case). In real transformer there is a leakage inductance that prevent ideal energy transfer. To deal with energy excess used primary side snubber circuit. This is RC or TVS, placed across primary side of transformer.Just diode will not work.https://ez.analog.com/cfs-file/__key/telligent-evolution-components-attachments/00-330-01-00-00-06-34-74/FlybackSnubberDesign.pdf&ved=2ahUKEwiH3Pnt3O-FAxX0S0EAHbiVDjwQFnoECBIQAQ&usg=AOvVaw3ODNdk6a17dTEQepZh68zlhttps://www.analog.com/en/resources/technical-articles/snubber-circuits-suppress-voltage-transient-spikes.html

author: Benta
author_rank: Super Contributor
timestamp: May 02, 2024, 08:37:13 pm
content: Quote from: nsled on May 01, 2024, 04:25:32 pmWon't work.You're storing energy in an inductor, and when your driving signal (your square wave) is turned off, that energy has to go somewhere.As xvr suggests, you can dissipate it in a TVS.You can also dissipate it in the load on the secondary side of the transformer (if there is a load). Or you can send it back on the power supply line by having a second primary winding connected through a diode to the main DC power input.

author: Terry Bites
author_rank: Super Contributor
timestamp: May 03, 2024, 01:16:54 pm
content: A snubber is a more suitable remedy

author: Benta
author_rank: Super Contributor
timestamp: May 03, 2024, 06:28:59 pm
content: Quote from: Terry Bites on May 03, 2024, 01:16:54 pmDoesn't really solve the problem, does it?From your PDF:· Reduce or eliminate voltage or current spikes· Limit dI/dt or dV/dt· Shape the load line to keep it within the safe operating area (SOA)· Transfer power dissipation from the switch to a resistor or a useful load· Reduce total losses due to switching· Reduce EMI by damping voltage and current ringingI see nothing about dissipating the energy stored in the inductor. Try again.
Flyback power supply output voltage - Page 1
Forum section: electronics / beginners

author: argintviu
author_rank: Contributor
timestamp: March 25, 2022, 11:48:49 pm
content: Hi all. I am working on a small step-up converter for a battery operated project and I discovered a little problem (LTSpice file and picture below).The circuit works as follows: The primary's swing is limited by the 30V Zener diode (which also protects the transistor). After passing through the 1:10 transformer, the energy is stored in C4. The expected voltage on the VOUT node would be 300V minus one diode drop, but it only gets to about 270V. Probing the VPULSE node shows that the output pulses dip below 0 quite a bit. Why is this occuring? Is this negative component normal for the flyback topology or am I doing something wrong?

author: xavier60
author_rank: Super Contributor
timestamp: March 26, 2022, 12:14:12 am
content: The negative half cycle at the secondary is due to VCC applied across the primary while Q1 is on and multiplied by the turns ratio.Although the Zenner is clamping the flyback pulse at the Collector of Q1 to 30V, the primary sees something less because of the presence of the VCC subtracting from it.

author: argintviu
author_rank: Contributor
timestamp: March 26, 2022, 09:40:42 am
content: Thanks, that's very helpful!
Flyback Transformer - Page 1
Forum section: electronics / beginners

author: khatus
author_rank: Regular Contributor
timestamp: August 03, 2018, 03:34:51 pm
content: Hi,This is Flyback Transformer also called Pulse transformer.Widely used in SMPS circuit.I have some Chinese smps. While i trying to reverse engineering those Smps,i have faced one problem i can not decide which one is primary and secondary,Auxiliary winding.It has 2 lead at one side and 4 lead at other side.Can anybody tell me how to decide primary secondary and Auxiliary winding.And how to determine the dot convention of those transformer??

author: ArthurDent
author_rank: Super Contributor
timestamp: August 03, 2018, 07:41:46 pm
content: The picture you posted of the transformer looks like a catalog picture. A photo of an actual power supply that you have would be a big help. If you have a SMPS that is all assembled then it should be easy to trace out the circuit. Generally the secondary is much lower voltage and higher current than the other windings so it probably have fewer turns of much larger wire.

author: khatus
author_rank: Regular Contributor
timestamp: August 03, 2018, 08:03:09 pm
content: Actually the smps still working well. I can desolder it.Its a 12V 2A SMPS

author: Jwillis
author_rank: Super Contributor
timestamp: August 04, 2018, 04:31:20 am
content: Its dependent on the circuit . Some times a secondary winding falls back to the High side of the SMPS to power the PWM.With these high frequency transformers its much harder to know by the resistance alone because of fewer winding s .Some can have as few as a half winding on a secondary.If its still in circuit the primary will be on the high side (mains input side) and will be tied to the drains of one or more MOSFETS and will have larger copper traces.If theirs a secondary on the high side will most likely be,but not directly , linked to the PWM .All remaining secondaries will be on the low voltage side.Think of the transformer as the border between the high voltage side and low voltage side.If the transformer is out of circuit and your unsure of the orientation then a arbitrary function generator can be used to find the pin outs of the transformer.If you have a function generator.
flyback voltage - Page 1
Forum section: electronics / beginners

author: macross
author_rank: Contributor
timestamp: February 20, 2014, 06:39:14 pm
content: I have built a pulse induction metal detector, but since it has some problems i need to use an oscilloscope to figure out whats wrong. But i'm concerned that flyback voltage from the coil might damage my scope, since it's rated only for 300vrms. I have read an article of another PI detector which also included scope images which showed flyback voltages of ~320v... Crazy!So could a flyback voltage damage my scope?

author: commongrounder
author_rank: Frequent Contributor
timestamp: February 20, 2014, 07:34:48 pm
content: When you start getting up into that voltage range, you should be using a 100x scope probe. Normally you would us the 10x probes that (I assume) came with the scope. This gives you,in theory only, 10 times the maximum voltage handling, i.e. 3000 volts max instead of 300volts, but most 10x probes have a much, much lower maximum voltage rating. Check the documentation that came with the probes. 100x probes divide the voltage by 100 which gives you a very comfortable margin and most 100x probes have a 1kv maximum voltage (again check the documentation). I use 100x probes for my work on vacuum tube amplifier circuits.Please be very careful around these voltages, as they can be fatal if contacted. Best to connect everything with power off and stand back for testing!

author: macross
author_rank: Contributor
timestamp: February 20, 2014, 08:06:26 pm
content: Checked my probe documentation it says x1 - 150v x10 - 300v so it's a no go.

author: commongrounder
author_rank: Frequent Contributor
timestamp: February 21, 2014, 02:25:29 pm
content: 100x probes can be had for reasonable prices from the 'bay. If you plan to scope out higher voltages very often, they are a good investment for safety of your scope inputs and for you as well. Best of luck!
FM Demodulators - Page 1
Forum section: electronics / beginners

author: helix1
author_rank: Contributor
timestamp: December 11, 2015, 01:52:23 pm
content: I am in the planning stages of a new project - building a basic compact FM receiver circuit. My requirements for the project are that it should receive a single frequency up to around 100MHz, the receiver should be battery powered and as small as possible without going to SMD components, and kept at a reasonable cost.I have been considering either a PLL approach or a quadrature demodulator approach so was wondering which might be better for my particular project.Any input would be really helpful, suggestions for good existing designs, PLL chips or mixers for the quadrature demodulator etc.

author: Cliff Matthews
author_rank: Unknown
timestamp: December 11, 2015, 02:12:53 pm
content: Lots to look at here:https://www.google.ca/search?biw=1280&bih=656&tbm=isch&q=transistor+only+FM+Demodulator

author: helix1
author_rank: Contributor
timestamp: December 11, 2015, 02:26:24 pm
content: Thanks Cliff, I've done some basic Google searches, and am now at the stage where I need a bit of guidance from an experienced hand to help zoom in on one of the better designs.

author: Ian.M
author_rank: Super Contributor
timestamp: December 11, 2015, 02:31:32 pm
content: Discretes only? If so, the most bang for your buck would probably be aFoster Seeley DiscriminatorHowever if you are willing to use ICs, and can source a N.O.S.Philips TDA7000, its more or less a complete FM radio on a chip, just add an AF amplifier, a tuned circuit for the L.O. and a few passives.Edit: you are lucky, Futurelec still have stock:http://www.futurlec.com/Philips/TDA7000pr.shtml

author: moya034
author_rank: Regular Contributor
timestamp: December 11, 2015, 03:46:47 pm
content: Quote from: Ian.M on December 11, 2015, 02:31:32 pmI agree.There are tons of good FM IC's out there which will outperform any thing you are likely to make with discretes most likely, no need to reinvent the wheel.

author: helix1
author_rank: Contributor
timestamp: December 11, 2015, 04:10:13 pm
content: Thanks for the tip - that IC looks perfect for the job. I will give it a go!
FM modulation in miniature transmitter - Page 1
Forum section: electronics / beginners

author: helix1
author_rank: Contributor
timestamp: December 30, 2015, 12:12:31 pm
content: I've been trying to understand the circuit shown below. I have a few questions that it would be great if someone could help me with.I don't really understand how frequency modulation happens in this circuit. From reading around, the general explanation seems to be that the amplified signal from the electret microphone somehow alters the internal capacitance of the transistor Q2 to create the modulation. Which junction capacitance is this that is getting altered? Is it the capacitance between base and emitter? How exactly is the capacitance being altered by the input signal?Also, C5 is providing the positive feedback to the emitter of Q2 in common base configuration. This looks like a Colpitts type setup, but why is the signal fed back through just one capacitor instead of the usual capacitive divider?

author: flynwill
author_rank: Regular Contributor
timestamp: December 30, 2015, 02:57:35 pm
content: The varying capacitance is the base-collector junction -- which, thanks to to C4, is effectively in parallel with C6.

author: helix1
author_rank: Contributor
timestamp: December 30, 2015, 03:36:22 pm
content: I'm still not clear how the capacitance of the base-collector junction changes with base voltage. Is this a documented effect?And the capacitor C4 is not always present in these kinds of circuits to put the base-collector junction in parallel with the tank circuit. For example, the circuit below. Is this still working the same way?

author: PA0PBZ
author_rank: Super Contributor
timestamp: December 30, 2015, 03:54:42 pm
content: Quote from: helix1 on December 30, 2015, 03:36:22 pmQuoteYes, look at the 1N and 22N

author: helix1
author_rank: Contributor
timestamp: December 30, 2015, 04:23:47 pm
content: @PA0PBZ that graph looks good. Where did you get it? I'd like to know how those curves are derived

author: PA0PBZ
author_rank: Super Contributor
timestamp: December 30, 2015, 05:45:44 pm
content: Quote from: helix1 on December 30, 2015, 04:23:47 pmIt was the 7thhit when I typed "collector base capacitance" in google image search, I just wanted to find something to show you that it was not imaginary

author: alterbaron
author_rank: Contributor
timestamp: December 30, 2015, 07:52:17 pm
content: There's some formulas here:http://ecee.colorado.edu/~bart/book/book/chapter5/ch5_6.htmThe capacitance in the base emitter junction is a consequence of voltage-dependent charge separation in the depletion layer. (When a change in voltage changes the amount of charge separation, you have a capacitance!)More details here:http://ecee.colorado.edu/~bart/book/book/chapter4/ch4_3.htmIn short, it turns out that you can treat the capacitance between the base and collector terminals as being due to a parallel plate capacitor, where the plates are separated further apart the higher the reverse bias the junction sees. I.e. the capacitance goes down with increasing reverse bias.
FM Radio signal improvement - Page 1
Forum section: electronics / beginners

author: WaynesWorld
author_rank: Contributor
timestamp: March 06, 2023, 07:22:20 am
content: I guess this a noob question so I'll ask here. How do I connect my FM radio Antenna to my house Antenna for better reception...I have an old Panasonic Tape/Radio/Alarm clock. I use the FM radio as the first alarm, and sometimes the reception can be patchy. It has a single wire Antenna, which I have tried connecting to the centre pin of a coax plug and to my house Antenna system but with no improvement. Yes, the Antenna was an Analog full VHF, at the time. I realise that FTA is horizontal and FM is vertical but I have had success doing this with other radios in the past.The issue I think, will be that the housing is plastic and there is no earth. Whats the best method here?

author: Terry Bites
author_rank: Super Contributor
timestamp: March 06, 2023, 08:45:26 pm
content: If your near to the station horizon and the signal is very low and intermittent, there's not a lot you can do.You'd need a very tall antenna to make a difference. Have you considered a VHF booster amp?Earthing VHF recievers doesn't usually help much. Give it a go if you like.https://www.ebay.co.uk/itm/314111654738?hash=item4922837b52:g:2TgAAOSwadli~XDf&amdata=enc%3AAQAHAAAA8EFZIQksl7P2o%2FtQ3%2FDkX%2BaSSW3%2BpCphSc8lsm5oHPiCg7g%2BmvlY5uKWg1glK%2FfK9EbeDlKqwaZRAUbt15eW3ZTM9fqV7e%2Blu5C2ty65pcEZWkST1hdTHyLqOxFAnMzwmu1pWR2Q0xgZRnkbA5nk7T177DpqUqP%2Fq4CpB9nIt8LSw69E4b55wkO%2FOTOsPL5vrwa0Hd8xxsMDmAiKRnyXEXrwCPHYMsvBaqJFjc9KFYB0cSn018FGvJ8fvB2lGeFse12VpfXS%2B4VQo6C%2BjpZqn4aGiRj24lZnUY11ntvrkrFxcJzrlhHNgGiTXTajG9xsUQ%3D%3D%7Ctkp%3ABFBM9NPcitdh

author: AFTORF
author_rank: Contributor
timestamp: March 06, 2023, 09:31:29 pm
content: Since some years, many indoor reception problems comes from EMI problems close to receiver. Low-cost Switching power supply and LEDs are the mainly source of interference in house.You could check if you are concern this problem like this :1) Use battery as power supply for your receiver.2) Switch off your main AC power supplyIf quality reception is better without AC in your home, you could use an outdoor antenna.

author: WaynesWorld
author_rank: Contributor
timestamp: March 07, 2023, 12:54:20 am
content: Quote from: AFTORF on March 06, 2023, 09:31:29 pmThere's not much near it. The clock radio is 2 pin AC only. 9v battery only for clock backup, which I don't think has ever worked.AC interference doesn't seem to be a problemQuote from: Terry Bites on March 06, 2023, 08:45:26 pmI have got decent FM from my outside Antenna on an AV receiver that has an actual 75Ohm connector. This radio only has a single wire, which when connected to the house Antenna didn't seem to make any difference.

author: AFTORF
author_rank: Contributor
timestamp: March 07, 2023, 07:03:25 am
content: The EMI problems are often radiated not conducted from domestic sources (PC, LED light, TV screen, IP Box). AC switch off is a test to check if you don't have any domestic noise generator in your home.
FM reciever project:  alignment without RF generator? - Page 1
Forum section: electronics / beginners

author: resurgance2001
author_rank: Newbie
timestamp: December 05, 2013, 07:40:14 am
content: Hi AllI am a newbie to this forum. I bought a kit in Thailand recently for a 2 IC stereo FM receiver.The first IC is a TA8127 Toshiba complete Fm tuner including stereo decoder. The kit only had instructions in Thai. There is an RF coil, two trimmer capacitors, a OSC coil, and IF transformer and and RF detector that all need to be aligned.I don't have an RF generator but I do have a scope that will display waves up to 100MHz and give a reading of the frequency up to 200 MHz.I tried (just for fun) to see if I could align it blind, just using my ear. All I think I have succeeded in doing is turn it into a slope detector, at least it has all the characteristics of super-regen and not a pLL receiver.Any suggestions? If it simply is not possible to allign it properly without an RF generator, how difficult would it be to build a really simply RF generator?Thanks in advance.PeterPS. I have been watching Dave's you tube videos for a while and think they are brilliant. Keep up the good work. Cheers

author: mhzghz
author_rank: Contributor
timestamp: December 06, 2013, 06:41:43 am
content: You can use the local oscillator frequency of a nearby radio as a signal generator.It may be 10.7 MHz higher (or lower) than the target frequency you need for alignment.Older Radio Shack scanners (PRO-2xxx series) are perfect for this, though they won't tune the FM broadcast band.

author: vk3yedotcom
author_rank: Frequent Contributor
timestamp: December 06, 2013, 09:36:41 am
content: Quote from: mhzghz on December 06, 2013, 06:41:43 amFurther to this I'd get two old-style (dial) battery powered FM broadcast receivers.Try to find the local oscillator of one on the other.Open one radio up.If you want an output connection or a stronger signal use (say) a 2pF capacitor connected to a few cm of wire and poke around on the circuit board (to find the output of the local osc) until the signal gets stronger. This may however detune its frequency.
FM TRANSMITTER - Page 1
Forum section: electronics / beginners

author: Adhith
author_rank: Frequent Contributor
timestamp: December 20, 2015, 05:54:22 am
content: hello everyone..iam working on a miniature fm transmitter & have connected most of the components. could you please tell me how to connect the electret microphone & also the connection from battery, i can't understand from the diagram. iam attaching the circuit diagram.

author: ataradov
author_rank: Super Contributor
timestamp: December 20, 2015, 06:44:26 am
content: What is not clear about the microphone? It has two pins, schematic has two points where those pins attach. Just do what the schematic says.The point with "+9 Volts" next to it is "+" of the battery, the node marked as ground (the bottommost wire on the schematic) is "-".But chances are that it will not work right away and will need tuning. Those FM transmitters can be fiddly to make work right.

author: vk3yedotcom
author_rank: Frequent Contributor
timestamp: December 20, 2015, 07:45:26 am
content: Some electret mics have three pins. You may need to connect one to the 10k resistor, another to the 0.1uF audio input and the other to ground. The ground pin is the one that, when checked with a multimeter, reads a short circuit to the microphone's metal case.
Trimmer Capacitors - Page 1
Forum section: electronics / beginners

author: Polybus
author_rank: Contributor
timestamp: May 30, 2015, 05:49:14 am
content: Following on from the success (??!?!?) of my recent AM Transmitter - I'm going to have a go at an FM one.I need a couple of 6pF to 40pF Variable Capacitors.Now here is the real newby question.Are these things Variable Capacitors??http://www.ebay.com.au/itm/50-x-40pF-6mm-2-Pin-Ceramic-Trimmer-Capacitor-Replacement-Yellow-/331551678628?pt=LH_DefaultDomain_15&hash=item4d320520a4They call them Trimmer capacitors - which I guess is just another name for Variable Capacitors, but in the specs they only nominate them as 40pF. I've seen very similar components that are adjusted with a little screwdriver.Specification:Product Name Trimmer CapacitorCapacitance 40pFMounting Type DIP Through HoleDiameter 6 mm / 0.24"Pin Spacing 5 mm / 0.2"Total Length 8 mm / 0.3"Material Ceramic, MetalWeight 16gMain Color YellowPackage Content 50 x Trimmer CapacitorsShould I just take it as assumed that they are 0pF to 40pF?? And they just leave the 0pF out of the specs because its just assumed?? Or am I missing something here?Thanks heaps.Polybus

author: ivaylo
author_rank: Frequent Contributor
timestamp: May 30, 2015, 06:18:01 am
content: Yes, they are variable capacitors. You can ask the seller what the range is. Here is a similar listing where it is spcifiedhttp://www.ebay.co.uk/itm/Ceramic-Trimmer-Variable-Capacitor-Green-5-2-40pF-2Pk-/121545592980Tolerance isn't great on these things though, so expect variation from they say the range is...

author: Polybus
author_rank: Contributor
timestamp: May 30, 2015, 07:06:46 am
content: OK thanks.From that answer I take it that I can't assume they start from 0pF.I'll write to the vendor and see what they say.Cheers.

author: SeanB
author_rank: Super Contributor
timestamp: May 30, 2015, 07:23:53 am
content: 40pF max, and probably minimum is 10pF or so. The low value ones are pretty poor, and you will find that they are fiddly to adjust, you need the right non metallic ceramic tool to do it.
FMMT597 transistor not working - Page 1
Forum section: electronics / beginners

author: Chris Hasler
author_rank: Newbie
timestamp: July 12, 2018, 02:01:04 pm
content: I have a transistor circuit which is not working properly. There are six of them all failing the same way.There is a PNP transistor (FMMT597, datasheethttps://www.diodes.com/assets/Datasheets/FMMT597.pdf) switching a 24V line to a LED and resistor.This is switched on/off from a 24V line via a potential divider.24V - 1k5 - Base - 12k - NPN transistor - 0VThe NPN transistor is triggering correctly, but the PNP transistor is continually passing 15V.Does anyone have any idea what I have managed to screw up on this?edit: I have swapped out the PNP transistor for a MPSA92G and achieved the same result, but with 15.6V passing the current.

author: Zero999
author_rank: Super Contributor
timestamp: July 12, 2018, 04:13:53 pm
content: Please post a schematic. It's impossible to know what the problem is, without one.

author: Chris Hasler
author_rank: Newbie
timestamp: July 13, 2018, 11:36:38 am
content: Please see attached image with the schematic and measurement points highlighted. The rest of the circuit is not attached to the connector at the moment.

author: Zero999
author_rank: Super Contributor
timestamp: July 13, 2018, 12:36:45 pm
content: The PNP transistors are connected backwards, so are behaving like 7V zener diodes. If the collector emitter connections are corrected, it should work, but it's also possible the transistors have been damaged, due to the reverse voltage. I recommend replacing the PNP transistors with new ones, connected correctly.The schematic is also drawn in a confusing manner, which makes mistakes more likely.

author: CJay
author_rank: Super Contributor
timestamp: July 13, 2018, 12:47:34 pm
content: Sure that schematic is correct only it looks wrong to me, emitters of the transistors should be connected to +V and collectors to 0V surely?*edit* damnit, Hero999 posted while I was editing

author: Zero999
author_rank: Super Contributor
timestamp: July 13, 2018, 12:59:03 pm
content: Dough, I wanted him to figure out the correct places for the collector and emitter connections.

author: CJay
author_rank: Super Contributor
timestamp: July 13, 2018, 01:08:34 pm
content: Ooops....'Left as an exercise for the reader'

author: Chris Hasler
author_rank: Newbie
timestamp: July 13, 2018, 01:15:30 pm
content: Didn't realise that the schematic would be wrong as its a rework of a through hole board to smd.So the next question is how did it work on the last 2 board revisions?I will have to work out if the boards are salvageable.

author: Zero999
author_rank: Super Contributor
timestamp: July 13, 2018, 01:50:40 pm
content: One possibility is the footprints for the transistors, on the previous board revisions, had their collector and emitter connections reversed, so it worked.

author: CJay
author_rank: Super Contributor
timestamp: July 13, 2018, 02:22:53 pm
content: Quote from: Hero999 on July 13, 2018, 01:50:40 pmOr if the last boards were through hole the transistors might just have been fitted bass ackwards and the schematic has never been correct...