hybridfree/eevblog-posts huggingface dataset:
Opto-isolated input ground - Page 1
Forum section: electronics / beginners

author: AdamSparky
author_rank: Newbie
timestamp: May 15, 2013, 12:48:15 pm
content: I have only just started learning to use optocouplers to provide circuit isolation.I would like to use an optocoupler to protect my microcontroller from the outside world, everything is run from the one power supply as per the attached circuit. I have both sides of the optocoupler attached to a common ground, this feels wrong, but don't know how it should be done.How is this situation usually handled?

author: SeanB
author_rank: Super Contributor
timestamp: May 15, 2013, 01:13:09 pm
content: Ideally you want a separate supply, otherwise all you need is a simple one transistor inverter or a protected voltage divider into a buffer chip. You are negating the use of the optocoupler doing what you did.

author: digsys
author_rank: Unknown
timestamp: May 15, 2013, 02:04:19 pm
content: There are reasons why people do it - some covered in this thread -www.eevblog.com/forum/projects/design-microcontroller-circuit-for-industrial-noisy-environment/msg209648/#msg209648In the simplest case, it offers a 2nd level of protection. Blowing up / then repairing an opto is a heck of a lot easierthan blowing up an MPU - in which case everything is dead.
Opto Isolator - Page 1
Forum section: electronics / beginners

author: Iano
author_rank: Newbie
timestamp: July 15, 2013, 02:49:08 am
content: Can anyone tell me if an opto isolator still protects circuits from each other when both ground pins of the chip are connected to a common ground?Surely current doesn't travel back across the internal LEDs??

author: kaz911
author_rank: Super Contributor
timestamp: July 15, 2013, 03:16:54 am
content: Try to remove the ground from your circuit pins and see if any current will flow. If there is no "ground" there is no current flow. The ground can be "floating" (think virtual ground) or the ground can be earth connected (like a normal bench oscilloscope). Ground is just a "definition"And one last pointer.. can you measure current on the negative cable from your power supply with a clamp meter? That is usually connected to your board's ground. And yes - you can measure current on your negative cable.If you accidentally attach 110/220v A/C to the input - what happens to your circuit?So yes - you can force current through your ground plane from "the other side" of an opto isolated circuit if you connect grounds together.

author: Iano
author_rank: Newbie
timestamp: July 15, 2013, 04:15:13 am
content: Thanks for the pointers. I will see what I can do.This is only a 40V DC (max) circuit.

author: kaz911
author_rank: Super Contributor
timestamp: July 15, 2013, 05:56:24 am
content: 40 v DC is actually quite a lot.. Dependent on the Amps of course.Anyway - post a bit more of what you are trying to do - and how you are powering it.I'm working with Isolated CAN at the moment - with DC power input either from CAN side or from both - and they need to be fully isolated as well.But why do you need to connect the two grounds together? can't you just keep them separate? or does your isolated side need to get DC power from other "other side"

author: Paul Price
author_rank: Super Contributor
timestamp: July 15, 2013, 09:58:41 am
content: The answer is no! If the grounds are connected together you have no isolation. Connected together means no isolation.It is possible to us an optocoupler for something other than isolation of grounds, for instance the output portion of the device can float within a circuit to function as a switch of a way to change the circuit it is meant to control and in this way isolating the controlled device circuitry from the ground-referenced control input. But if the two grounds are tied together, this idea is to control something with the optocoupler's output and to not achieve ground isolation.
Opto-Schmitt question  - Page 1
Forum section: electronics / beginners

author: Chris Wilson
author_rank: Super Contributor
timestamp: July 29, 2019, 01:16:36 pm
content: I am experimenting with an opto-Schmitt device, an H11L1M. If I input a sine or square wave of 50% duty cycle I can only get the same duty cycle on the output pins at a certain input LEVEL. If I go under or over that level the duty cycle changes from the original signal's 50%. I assume this must be normal? If so why does this occur please? Thanks.www.farnell.com/datasheets/1793287.pdf

author: soldar
author_rank: Super Contributor
timestamp: July 29, 2019, 04:42:05 pm
content: While somebody else more knowledgeable comes along my guess is that all semiconductor switches have inherently certain Ton and Toff delays cause by different factors and only under certain circumstance would the delays be equal thereby preserving the duty cycle.

author: David Hess
author_rank: Super Contributor
timestamp: July 30, 2019, 09:24:11 pm
content: Square wave drive should produce a constant duty cycle on the output.The input is suppose to be driven with a current and not a voltage.

author: schmitt trigger
author_rank: Super Contributor
timestamp: July 30, 2019, 09:38:29 pm
content: Take a two-channel scope, and overlay the input and output waveforms, to determine the threshold changes.If you have a trianglewave signal generator, it becomes far easier.

author: magic
author_rank: Super Contributor
timestamp: July 30, 2019, 09:45:29 pm
content: I played with this device at one point. Both things are true.There is some LED current threshold which turns the output on and another (lower) which turns it off. So if your current waveform isn't symmetric around those points, output duty cycle has no reason to be 50%.At high speeds propagation delays become significant and they may be asymmetric and dependent on things like output pullup resistance and input current limiting resistor. Getting 50% duty cycle at 1Mbps takes some tweaking.In fact, propagation delay is so long that it approaches one full bit time at circa 1.3Mbps, right before the device gives up and starts dropping bits. It's fun to watch on the scope as input and output change their state almost in unison, even though it is an inverting device.
Optocouler using transistor... - Page 1
Forum section: electronics / beginners

author: Kedar264
author_rank: Regular Contributor
timestamp: March 08, 2015, 06:32:16 pm
content: Transistor turns on when mentioned base current is provided ,but the process behind it is to generate small amount of carriers in base regionWe can do this by shining light (of suitable wavelength) on to the semiconductor of the transistorSo, I've opened 2n2222a transistor and spotted under the laser and here's the result, it worked!!!Maybe this can be used as an optical isolator or optocouplerSee the videohttps://youtu.be/hdIEQJqHyvI

author: xrunner
author_rank: Super Contributor
timestamp: March 08, 2015, 06:41:05 pm
content: Yea it's interesting and fun but they already make them - they are called phototransistors -Quote

author: JohnnyBerg
author_rank: Frequent Contributor
timestamp: March 08, 2015, 06:42:50 pm
content: I remember scraping of the paint of a OC71 end 60's.Yes, it works, even after 45 years

author: T3sl4co1l
author_rank: Super Contributor
timestamp: March 08, 2015, 08:35:30 pm
content: Yup!Likewise, you can use a photosensor as a transistor, if the semiconductor is accessible in some way (electrical connection or electric field). FET example:http://sparkbangbuzz.com/cds-fet/cds-fet.htmTim
Optocoupler collector-emitter leakage - Page 1
Forum section: electronics / beginners

author: gus789
author_rank: Contributor
timestamp: December 13, 2016, 06:21:19 am
content: Hi,I am trying to use the circuit in the diagram to a generate 0-10V dimmer signal for a LED driver. The input is a PWM signal from an arduino (0-5V). The problem is that the voltage at the output only goes down to 2.56V minimum. The datasheet for this couplerhttp://www.mouser.com/ds/2/427/tcet1100-240288.pdfsays the max collector emitter cut off current is 100nA, which should translate to a negligible drop across the 12kOhm when the coupler is off. Am I missing something obvious or is there something wrong with the circuit?Thanks!

author: mij59
author_rank: Frequent Contributor
timestamp: December 13, 2016, 06:32:54 am
content: Check the collector and emitter connections, they could be reversed.

author: Seekonk
author_rank: Super Contributor
timestamp: December 13, 2016, 06:45:06 am
content: Something is wrong. I use this circuit as a quick and dirty high side FET driver at my camp with a 300K resistor and there is no noticeable leakage.
optocoupler CTR calculation - Page 1
Forum section: electronics / beginners

author: JeanF
author_rank: Regular Contributor
timestamp: May 18, 2020, 01:42:20 pm
content: Hi,I was not sure how to use the various CTR graphs that are included in optocoupler datasheets, and I came across this documenthttps://www.vishay.com/docs/83706/83706.pdf(funnily enough I also found another one by the same manufacturer titled "Guidelines for Reading an Optocoupler Datasheet", at least they now that it can be confusing for beginners)and I figured I could do a bit of homework while I'm at it.Then in Problem 1, step 2, equation 2 (in page 2), where does the IL= 50 µA come from ? Maybe it has to do with the leakage current of the 74HC04 but in the datasheets I found it's spec'd at +/- 1 µA, which is far from 50, so I'm not sure.Thanks!EDIT :By the way, I was reading this thread on RPi forumshttps://www.raspberrypi.org/forums/viewtopic.php?f=37&t=54024which is about ways to use an optocoupler in the most reliable (and hopefully safe) manner to detect if mains is live or not from a Raspberry Pi or another low voltage device.Somewhere in the middle, the author (Bud Bennett) says " So we now know that the output current is 100uA. The CTR of the 4N37 is estimated, using Figures 3 and 5 and iterating a bit, to find IF produces a CTR of about 0.15."(sorry, can't provide a direct link, please use Ctrl-F to find where it is in the rather lengthy post)the link to the datasheet he used is broken but I managed to find it with archive.org wayback machine,I've attached it here.Could someone help me replicate his estimation of 0.15? The best way could be to ask him directly but I don't have an account in RPi forums, and replying to a 7yr old thread is often considered bad etiquette...he is using IF= 1 mA to reduce LED aging. When I use fig. 3 with IF= 1 mA, I find the normalized CTR is about 0.9... even multiplied with the worst case 40% CTR @ 100°C, that's about 0.36, quite far from 0.15... and I don't know how to use fig. 5 in this case. Is it possible to extrapolate from the three curves shown?thanks again

author: David Hess
author_rank: Super Contributor
timestamp: May 18, 2020, 02:59:01 pm
content: That looks like the leakage from all sources including the HC logic input and they massively overestimate it just to be sure. I would have ignored it when operating at 150 microamps.
Optocoupler - dual, but "back to back"?? - Page 1
Forum section: electronics / beginners

author: max_torque
author_rank: Super Contributor
timestamp: April 04, 2015, 03:10:36 pm
content: I'm trying to find a dual optocoupler, ideally in a SO-8 package that has it's channels oriented "back to back" so that in effect i have the signals crossing the isolation barrier in opposite directions. I'm pretty sure this must exist, but obviously "back2back" isn't the right phrase to search for! What do you call such a device?

author: Ian.M
author_rank: Super Contributor
timestamp: April 04, 2015, 03:38:10 pm
content: Google: bidirectional dual opto

author: wraper
author_rank: Unknown
timestamp: April 04, 2015, 03:38:21 pm
content: "Bidirectional".http://uk.farnell.com/avago-technologies/acsl-7210-00re/optocoupler-digital-bi-dir-3750vrms/dp/2368140?ost=ACSL-7210http://uk.farnell.com/fairchild-semiconductor/fod8012r2/optocoupler-so-8-bi-directional/dp/2083181?ost=fod8012Two separate optocouplers would be much cheaper though. Especially if you need something low speed.

author: max_torque
author_rank: Super Contributor
timestamp: April 04, 2015, 08:23:17 pm
content: "bidirectional" seems to get me expensive devices that can actually send data in both directions across the isolation gap. What i want is to be able to send data in a single direction per channel, but that each channel should be in opposing directions! ie instead of having both LED's on one side, and both LDDs/transistors on the other, the device has one LED & one LDD/transistor on each side?

author: wraper
author_rank: Unknown
timestamp: April 05, 2015, 01:45:00 am
content: Quote from: max_torque on April 04, 2015, 08:23:17 pmYou are saying obvious. I rather assume you cannot read the datasheets properly, not we understand you wrong. Devices on the both links I provided do have 2 independent channels, except the power pins of course. Cheapest I can find at farnellhttp://uk.farnell.com/avago-technologies/acsl-6210-00re/optocoupler-smd-dual-bi-dir/dp/9130144
Optocoupler led - Page 1
Forum section: electronics / beginners

author: Raj
author_rank: Frequent Contributor
timestamp: September 20, 2020, 05:35:03 am
content: How come we never see leds lighting up at under 3v, outside of optocouplers? (sometimes even 1.5v)How strong (optical power/ electrical watts) would they be, outside of optocoupler? compared to standard ir led

author: greenpossum
author_rank: Frequent Contributor
timestamp: September 20, 2020, 05:45:45 am
content: What do you mean? The forward voltage drop of a typical red LED is between 1.7 to 2V.

author: magic
author_rank: Super Contributor
timestamp: September 20, 2020, 07:13:35 pm
content: I believe voltage drop is mainly a function of color, something to do with individual energy of emitted photons and stuff like that. IR is the lowest, UV is the highest. White is a modified blue LED so also quite high.

author: Benta
author_rank: Super Contributor
timestamp: September 20, 2020, 07:20:04 pm
content: Optocouplers use IR-LEDs.The >3 V you're quoting are for blue LED's (that can be converted to white with a fluorescent coating).

author: wraper
author_rank: Unknown
timestamp: September 20, 2020, 07:23:21 pm
content: Quote from: magic on September 20, 2020, 07:13:35 pmOnly sort of. LEDs are made by using different technologies. Thus LEDs of the same color have different forward voltages.

author: Raj
author_rank: Frequent Contributor
timestamp: September 22, 2020, 12:10:06 pm
content: I've been overvolting leds for such a long time**Except when the seller stated what voltage it should run at

author: BravoV
author_rank: Super Contributor
timestamp: September 22, 2020, 12:12:46 pm
content: You should learn what is called constant current driven device.

author: Raj
author_rank: Frequent Contributor
timestamp: September 22, 2020, 12:21:26 pm
content: Quote from: BravoV on September 22, 2020, 12:12:46 pmYes indeed. Used them with lasers since their forward voltage is all over the place depending on uncontrollable factorsWith Led, I was like, eh, 3v is ok... if the current and supply voltage is high, like for flashlight, I just throw an LM317(easy to use constant current driver, but I'm looking to find better, more efficient drivers) in there set usually at 75% of max current.
Optocoupler protection - Page 1
Forum section: electronics / beginners

author: cosminnci
author_rank: Regular Contributor
timestamp: April 03, 2013, 06:15:59 pm
content: Hello,I use a transformerless power supply from Microchip AN 954, the purpose of this is to detect on off from an microcontroller.I have the setup as in attachmentso far from my tests when I get a power fluctuation or a spike the optocoupler output is dimming and finally burns out.how can I protect the optocoupler from this?, maybe somme shotky diode near the zener?thank you.regards,Cosmin

author: SeanB
author_rank: Super Contributor
timestamp: April 03, 2013, 06:50:59 pm
content: Make R2 higher in value, 1k is better, it will dissipate a little more power. R11 can be 1k, this reduces the current through the opto to be lower, making the LED last longer. Instead of the LED on the output, use a 10k resistor and a low current LED, as this is a low transfer ratio unit, so it will have at most a 500uA drive capacity. C5 can be 47uF, and add a VDR across the input, 275VAC will do. This will make the opto last longer.

author: Alana
author_rank: Frequent Contributor
timestamp: April 03, 2013, 07:32:29 pm
content: If it goes bad on brown out it means that phototransistor in the optocoupler has too little light from LED to go into saturation and starts working in linear mode - and this means heating up and eventually damage. VDR or other over voltage protection tricks wont work here.Minimizing current via phototransistor may do the work. Try this :

author: cosminnci
author_rank: Regular Contributor
timestamp: April 03, 2013, 08:38:33 pm
content: The calculations for the values are from this form:http://www.daycounter.com/Circuits/Transformerless-Power-Supplies/Transformerless-Power-Supplies.phtmlwith R1 220 and C1 0.33uF the circuit produces 5.1v, 12.9mA and R1 dissipates 0.168Wthe 4n25 is calculated to be powerd with 1.5v 10mA and the R11 value of 390 would limit the current, the opto max is 60mAreplacing with 1K the R2 would dissipate 0.68W and produce 12.1mA, not much change, the power is calculated to be dissipated trough R1 and R11 in either combination.during normal operation all look well but during a spike the led from the opto gets damaged the part after is not too relevant the other led is for local test and can be ignored.I will try a varistor.does the zener diode actualy work in this circuit? do I need it?

author: SeanB
author_rank: Super Contributor
timestamp: April 04, 2013, 05:37:37 pm
content: The zener is needed, it limits the forward current applied to the LED. You can place a 1n4001 in parallel with it as well, as some zener diodes are composed of a single zener diode in series with some forward biased regular diodes.

author: cosminnci
author_rank: Regular Contributor
timestamp: April 04, 2013, 07:52:21 pm
content: I tested today and managed to damage the zener, it started conducting, but the opto was fine.I tested extreme conditions that should never occur (shorted the power resistor).will test the 1n4001 diode solution but I hope I won`t need it.thank you.regards,Cosmin
Optocoupler Reverse Active mode - Page 1
Forum section: electronics / beginners

author: csheldon
author_rank: Contributor
timestamp: March 23, 2019, 07:27:25 am
content: Hi.Can someone explain how will the optocoupler behave in reverse active mode, if we swap the transistor side leads (swap C-E)?Lets take for example PC817. This is what I found in datasheet for normal active mode if we set the current of the internal LED to 1.9mA:PC817 Forward Current If = 1.9mAPC817 Forward Voltage Vf =1.4VPC817 transfer ratio @ 1.9mA = 670%PC817 max collector current @ if->1.9mA Ic=12.73mACan someone now explain how will these parameters change if we reverse the C and E leads of the optotransistor side?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: March 23, 2019, 09:01:09 am
content: No idea, it's not spec'd.It may just be the raw photodiode current, since the photosensitive area is, I forget what it is -- is it a thick collector region beneath a thin emitter and base, so the photodiode is effectively the C-B junction, which in turn causes B-E current and amplification? Or is it the other way around, thick emitter or base near the top?In any case, you'll have to characterize it yourself.Tim

author: David Hess
author_rank: Super Contributor
timestamp: March 23, 2019, 03:26:22 pm
content: I know I measured it once but I do not remember how much difference there was between the photodiode collector-base current and base-emitter current. I was interested in using standard cheap 4N35s as low voltage current sources for single supply applications and they worked great. Want a true zero input or output with a single supply? This works great although it costs power.The phototransistor will happily work with the collector and emitter reversed but the reverse beta (current gain) is low limiting current transfer ratio and of course the reverse collector-emitter breakdown voltage is only like 5 volts.
Optocoupler to microcontroller input  - Page 1
Forum section: electronics / beginners

author: villager
author_rank: Newbie
timestamp: April 23, 2014, 02:10:09 pm
content: I'm doing some simulations with optocoupler as a switching circuit to isolate between between high voltage input and a PIC16F690 mcu. Using Proteus simulator, I made the following circuit:The forward current and typical voltage for the LED of the 4N25 are 50 mA at 1.3 V typically as rated in the datasheet. The 215 ohm anode resistor was calculated based on an assumption that the input is a 12V swinging signal (high and low), which I mimic by using a button, so it was chosen to provide the 50mA current at 1.3V drop for the LED. The 10Kohm pull-down resistor is used so that whenever the input signal is high, the collector will conduct current via the 5V supply down through the emitter.I wrote code that tells whenever the signal at RB4 is high, RC0 goes high and the blue LED illuminates. Whenevr RB4 goes low, RC0 goes low and the blue LED turns off. The code is written using Mikroc IDE.Code:void main() {ANSEL = 0x00;TRISC = 0x00;TRISB=0xFF;PORTC = 0x00;OSCCON = 0b01110001; /* set internal clock to 8 MHZ */OSCTUNE = 0x1F;for(;;){if(PORTB.B4==1){PORTC.B0=1;}elsePORTC.B0=0;}}The problem is that when I run the simulation, the blue LED doesn't illuminate regardless of the button state (pressed or not). But when I reverse the condition statement to if(PORTB.B4==0), it illuminates. It's been so long since I typed a code, so it could be a problem in code, configuration or hardware. What do you suggest?

author: Skimask
author_rank: Super Contributor
timestamp: April 23, 2014, 03:24:19 pm
content: Quote from: villager on April 23, 2014, 02:10:09 pmQuoteQuoteQuoteJust one code?QuoteBuy some real physical hardware and forget the simulators...

author: Kjelt
author_rank: Super Contributor
timestamp: April 23, 2014, 05:34:20 pm
content: I personally always ground the emitter of a npn transistor and place a resistor in series with the supply and the collector.Then place the input of the microcontroller at the collector and it should be '1' when optocoupler is off and '0' when on.Quotesounds more like a maximum current then typical, at 5mA - 10mA it should already conduct.

author: villager
author_rank: Newbie
timestamp: April 23, 2014, 08:20:38 pm
content: I tried doing the pull-up resistor but it changes nothing. I used the voltmeter to see if there's voltage between the terminals of the pull-down resistor when I press the button, and yes, there's around 4.9 volts. When the button is not pressed, it reads 0 volts of course. It's really weird. Could it be a problem with the simulator? I look for other answers.
Optocoupler - Page 1
Forum section: electronics / beginners

author: mclaugh100
author_rank: Newbie
timestamp: February 20, 2014, 11:20:56 am
content: I have an optocoupler that I need to find out information on.Can anyone tell me what the numbers mean on the top of the chip?It reads like this 4N26V 313 A63Thanks in advancePat

author: Rerouter
author_rank: Super Contributor
timestamp: February 20, 2014, 11:23:47 am
content: http://www.vishay.com/docs/83725/4n25.pdf
Optocouplers --  Collector dark current vs Off-state collector current - Page 1
Forum section: electronics / beginners

author: MicroControllerGuy
author_rank: Newbie
timestamp: March 16, 2019, 05:35:12 pm
content: If i place a voltage across the Collector-Emitter of an octocoupler when the LED is completely off, what is the datasheet term for the Collector-Emitter leakage current?Is it the "Off-state collector current", or the "Collector dark current?I found this definition of collector dark current on a website:"When the phototransistor is placed in the dark and a voltage is applied from collector to emitter, a certain amount of current will flow. This current is called the dark current (ID). This current consists of the leakage current of the collector-base junction multiplied by the dc current gain of the transistor. The presence of this current prevents the phototransistor from being considered completely "off", or being an ideal "open" switch."If the quote is correct, what is "Off-state collector current"?Here is an example of a datasheet specifying both parameters (Toshiba LTP185):https://toshiba.semicon-storage.com/info/docget.jsp?did=14111&prodName=TLP185(SECan someone please tell me the difference between these two currents, I'm confused?Thanks!

author: magic
author_rank: Super Contributor
timestamp: March 16, 2019, 05:48:18 pm
content: One is specified for Vf=0.7V, the other presumably for Vf=0.Extrapolate figures 11.4 and 11.9 to see what's likely to happen at Vf=0.7V.Friendly reminder to always look at test conditions, including those "unless stated otherwise" at the top. These really define what the spec means in practice, not just the spec's name.That being said, I think in most optocoupler datasheets "dark current" will be the exact thing you are looking for.

author: MicroControllerGuy
author_rank: Newbie
timestamp: March 16, 2019, 06:13:32 pm
content: Thanks for the reply, Magic, this makes sense nowI guess if Toshiba had specified 'VF = 0" in the Test Conditions for the Dark Current, or had specified IF down to 0.0mA in figure 11.9, it would have been more obvious to me.
Optoisolator CTR 100% or 35% - Page 1
Forum section: electronics / beginners

author: Poe
author_rank: Frequent Contributor
timestamp: December 14, 2019, 05:34:49 pm
content: The below datasheet lists a minimum CTR of 100% at table 4.2, yet graphs 4 and 11 imply 35% MAX.http://optoelectronics.liteon.com/upload/download/DS-70-99-0012/4N3X%20Series%201115.pdfBefore I contact them, just wanted to check to see if I'm missing something.

author: David Hess
author_rank: Super Contributor
timestamp: December 14, 2019, 07:33:58 pm
content: It looks like a mistake to me.

author: MagicSmoker
author_rank: Super Contributor
timestamp: December 14, 2019, 11:57:53 pm
content: Yeah, the 100% CTR at 10mA spec is definitely a typo; the figure 4 graph looks about right for a 4N25/4N35 series opto.
orange pi one, is WIFI worth it? - Page 1
Forum section: electronics / beginners

author: MechEng87
author_rank: Contributor
timestamp: October 31, 2016, 09:55:42 pm
content: Hello again, I'm fairly new and this is only my second posting. I have gotten myself a few orange pi one's recently and I am trying to set them up on my home wireless network. I got some wifi dongles from edimax, EW-7811Un and am trying to get the orange pi ones on the wireless. I have very little to no knowledge of Lunix programming or the environment in particular but I am learning. I have the ethernet working fine and I am running Debian system Armbian 5.20. I have tried looking online but there seems to be very little support for the PI one in this topic. If anyone has some ideas or places I could go to learn the methods to get the solutions I seek, I would be very greatfull. my end game at this point is to get my two orange pi's and my other computer with the external hard drive set up on tjhe same network worelessly so i dont have to deal with ethernet cables.
OrCAD - temperature analysis help - Page 1
Forum section: electronics / beginners

author: username
author_rank: Newbie
timestamp: February 18, 2017, 08:51:23 am
content: I have a basic circuit with a diode, resistor, and a voltage source. I am getting the following error when trying to change the X Axis variable toVd(diode voltage):ERROR(ORPROBE-3217): Only 1 expression allowed for the X variable.I have set three different temperatures inTemperature (Sweep). Default variable for X Axis is the voltage source, and when trying to change it toV(D1)which is a diode voltage, it gives the above error.My question is how to get diode characteristic (or any other characteristic)Id=f(Vd)when multiple temperatures are used in the same simulation?
modelsim force input simulation.  - Page 1
Forum section: electronics / beginners

author: hatokay
author_rank: Newbie
timestamp: January 10, 2019, 12:55:18 pm
content: this software is a nightmare!!i have a simualtion running, it is a 32bit multiplier.but for some reason when i force a "10" it outputs "16".so for example if i try to multiplie 10*2 it gives me the result 16*2 =32;i put the radix in decimal but it still goes on like this. why?btw, its like that with all the numbers with zero, meaning 20 is 32.

author: andycsmith
author_rank: Contributor
timestamp: January 10, 2019, 04:27:54 pm
content: I know nothing about the software but it looks like its accepting Hexadecimal numbers and converting to DecimalHex Decimal10 1611 171A 2620 32etc
Ordered FX-888, received FX-888D? - Page 1
Forum section: electronics / beginners

author: dnix
author_rank: Newbie
timestamp: April 30, 2013, 06:57:58 pm
content: Not sure if the seller ran out, it was an accident, or what. This is my first actual soldering station. My research pointed towards the Hakko, but also that the digital version wasn't "all that".Should I just keep it? What would you do?

author: eKretz
author_rank: Frequent Contributor
timestamp: May 01, 2013, 12:37:45 am
content: I would just keep it if I were you. Look at it as a free upgrade. I'm not sure why the digital version wouldn't be as good as the analog, unless it's just down to personal preference.

author: dnix
author_rank: Newbie
timestamp: May 01, 2013, 01:44:04 am
content: It seems to me like the knob could easily outlive the digital controls.But hey, I don't know! Maybe I'll keep it.

author: Psi
author_rank: Super Contributor
timestamp: May 01, 2013, 01:46:29 am
content: Who did you order from?I wouldn't mind a FX-888D for FX-888 price.And if they ship a normal FX-888 so be it.Personally I like being able to read the digital temperature at a glace without having to see where the knob is at.

author: dnix
author_rank: Newbie
timestamp: May 01, 2013, 02:04:47 am
content: Quote from: Psi on May 01, 2013, 01:46:29 amA vendor on eBay who sells lots of Hakko stations.The price difference isn't more than $10 nowadays. I realize the FX-888 is discontinued, but the seller has stock listed. I guess this was just a mistake.
Ordered some opamps - Page 1
Forum section: electronics / beginners

author: lordvader88
author_rank: Frequent Contributor
timestamp: March 21, 2019, 12:40:15 am
content: I have lots of LM358, LM386, a few TL082 or 072, and not much else. So it's about time I ordered some, even anything cheap is better for now. So I orderedLMC6482LT1013NE5532What are they like for low level hobby use, any suggestions for the next $20 worth ?

author: Audioguru
author_rank: Super Contributor
timestamp: March 21, 2019, 12:56:35 am
content: The datasheets tell you all about the opamps.The LMC6482 is Cmos rail-to-rail so its max output current is low, its gain with a fair load resistance is low, its max allowed supply is only 16V and it is noisy.The NE5532 is an old audio opamp with low noise and the ability to drive a 600 ohm load well.I did not look at the LT1013.

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: March 21, 2019, 02:05:31 am
content: Hi,The LT1013 does not have the standard pinout in the SMD SO package:Regards,Jay_Diddy_B

author: bson
author_rank: Unknown
timestamp: March 21, 2019, 03:07:26 am
content: Quote from: Audioguru on March 21, 2019, 12:56:35 amWell, it's an old audio opamp that will drive loadsdown to600Ω well... A modern opamp like an LME49720 will drive anything you care to hook up - 30Ω headphones, an 8Ω PCB mounted transducer... with an order of magnitude lower output impedance the load is not even a specified test condition. If it's a sensible load, it'll drive it.
ordered wrong voltage cob led lights - Page 1
Forum section: electronics / beginners

author: ME
author_rank: Frequent Contributor
timestamp: April 05, 2025, 09:02:41 am
content: I ordered 115v led cob lights in error, I meant to order 230v ones, Can i run 2 of the 115v ones on 230v and wire them in series?https://www.aliexpress.com/item/1005003189658696.html?spm=a2g0o.order_detail.order_detail_item.3.7035f19chN01QR

author: ME
author_rank: Frequent Contributor
timestamp: April 05, 2025, 03:09:38 pm
content: Can anyone answer this?.

author: Xena E
author_rank: Frequent Contributor
timestamp: April 05, 2025, 04:32:47 pm
content: No.Options:transformer.Modify for 230. (The Data sheet for the driver chip will give clues how to do that, or order a 230 one and compare.)

author: ME
author_rank: Frequent Contributor
timestamp: April 06, 2025, 08:22:14 am
content: well i wired 2 cob led units in series and they seem to run fine on 230v.

author: Gyro
author_rank: Super Contributor
timestamp: April 06, 2025, 08:41:12 am
content: Well you'd better check that they are sharing the voltage equally then.

author: Xena E
author_rank: Frequent Contributor
timestamp: April 06, 2025, 10:54:53 am
content: Quote from: Gyro on April 06, 2025, 08:41:12 am...And hope that one of them never becomes faulty...Just because you can doesn’t mean you should.Xena

author: SteveThackery
author_rank: Super Contributor
timestamp: April 06, 2025, 12:58:58 pm
content: Quote from: Gyro on April 06, 2025, 08:41:12 amSo, is it possible that the 240V product is just two of the 120V product in series?

author: Xena E
author_rank: Frequent Contributor
timestamp: April 06, 2025, 01:12:27 pm
content: They have on board drivers, the problem will be when one starts to current hog at some point, even if they're balanced to start with.There is probably little difference between the two modules and it may be possible to hack one to the other supply easily. It depends on the arrangement of leds in the cob, and if it is a switcher supply or linear type.I bought a few similar units (coloured), they had linear current regulation and the difference was the configuration of the cob LEDs so not hackable to a lower supply had I wanted to.As an aside those were claimed as 50Watt but were nearer 10!Worked OK though.X

author: tunk
author_rank: Super Contributor
timestamp: April 06, 2025, 04:37:10 pm
content: From the one of photos in the aliexpress listing,the board is marked with 110V and 230V. There'salso three jumper positions and a guesstimate isthat they are used for setting voltage. You couldget another 230V version and see what the differenceis (or do a web search to see if you can find outmore).

author: Zero999
author_rank: Super Contributor
timestamp: April 07, 2025, 12:47:14 pm
content: Quote from: ME on April 05, 2025, 09:02:41 amWhy not simply return them?You're in the UK, which mean the distance regulations apply, so you can return them and only have to pay postage.
Ordering Reels - Page 1
Forum section: electronics / beginners

author: krivx
author_rank: Frequent Contributor
timestamp: July 31, 2013, 01:10:51 pm
content: I need to order some parts for a build that has a bunch of 0805 passives. The BOM for the boards I have lists some thick film resistors that are only available in minimum quantities of 5000. I can just find an alternative part, but working out the reel costs shows they are much cheaper than I would've thought, usually 10-15€ for 5000 resistors. Is getting a couple of reels in common values a terrible idea? Having stock is always nice but I'm a little worried I'll be carrying around these reels for the rest of my life. I don't do any production building right now, just hobbyist stuff and one-offs for work.

author: Psi
author_rank: Super Contributor
timestamp: July 31, 2013, 01:21:15 pm
content: A few common values is a good idea, maybe 1k and 10k, but i wouldnt get more than thatWhats so special about the resistors that makes them only available in reels?

author: krivx
author_rank: Frequent Contributor
timestamp: July 31, 2013, 01:26:34 pm
content: Quote from: Psi on July 31, 2013, 01:21:15 pmYeah, I was thinking 1k, 10k, 100k. Maybe 0805 100nF ceramic caps as well.Nothing special, the P/N was just for parts packaged as a reel. It's not unusable to have a separate P/N for a reel service with some suppliers.
ORG1411-PM04 GPS module - I2C integration without 1.8V - Page 1
Forum section: electronics / beginners

author: timmbo
author_rank: Newbie
timestamp: January 08, 2020, 04:01:00 pm
content: Hi all,I'm currently designing a circuit including the small ORG1411-PM04 module, which runs on 3.3V (the PM01 runs on 1.8V).I would like to avoid an external 1.8V LDO, but now ask myself if the I2C SCL and SDA lines will work (IO output level of the ORG1411 is 1.8V). They are pulled up by 4.7k to 3.3V (near my ESP32 MCU).The ORG1411 datasheet says:"SCL and SDA are pseudo open-drain lines, therefore require external pull-up resistors of 2.2kΩ to 1.8V, or 3.3kΩ to 3.3V.".Means it should work, right? Even if SCL and SDA are on 1.8V level on ORG1411 side and 3.3V on MCU side? I'm not a big I2C expert.I attached the schematic (without the 4.7k pull-ups for I2C, they are located near the ESP32 MCU).Thanks in advance,Timm

author: mvs
author_rank: Frequent Contributor
timestamp: January 09, 2020, 12:41:45 pm
content: Quote from: timmbo on January 08, 2020, 04:01:00 pmYesQuoteYou will get I2C with 3.3V levels on both sides. But it is fine, since ORG1411 inputs are 3.3V tolerant and I2C output (SDA) is open drain.

author: timmbo
author_rank: Newbie
timestamp: January 09, 2020, 04:31:42 pm
content: Cool, thank you very much for the help! Greets, Timm
organ keyboard reed switches - Page 1
Forum section: electronics / beginners

author: minibutmany
author_rank: Regular Contributor
timestamp: July 23, 2014, 05:17:17 pm
content: Lately I have been working on a pipe organ project and right now i'm trying to get the keyboard to work a bit better. I was thinking I would replace the mechanical switches with reed switches so that it wouldn't have that "click" when you push the key down. I Don't know much about reed switches and I was wondering if I would even be able to use them in such close proximity of each other, about a 1/2 inch apart. My fear is that when the magnet comes down to the switch it will trip the other switches around it. Will this be a problem and is there anything I should look for on the data sheet? Thanks.

author: Richard Crowley
author_rank: Super Contributor
timestamp: July 23, 2014, 05:27:29 pm
content: Are you sure you want to remove the tactile "feel"? One of the great disadvantages of electro-pneumatic pipe organs is that they remove all the "feel" from the keyboard. And it ends up feeling like pushing an electric doorbell button.That is why people still make "tracker" organs with hard mechanical linkage between the key and the "pallate" valve. Here are photos I took at the Rieger Orgelbau factory in Bregenz, Austria...

author: minibutmany
author_rank: Regular Contributor
timestamp: July 23, 2014, 05:34:27 pm
content: The tactile feel I was getting from these switches was nothing like a tracker organ. I have considered doing a complete tracker overhaul of the project, when I started this two years ago my woodworking skills weren't really up to the task of completely mechanical. I have never played an electric organ that felt anything like a tracker so I don't really see how I could come close to replicating that. The main advantage to the reed switch is that the pipe can start to play before the key is all the way down, then I could use some felt pads as a depth stop.
orico usb mod - Page 1
Forum section: electronics / beginners

author: radish
author_rank: Contributor
timestamp: April 17, 2016, 01:32:54 am
content: Hey guys, and gals.i went out and got one of thses over priced usb chargers this weekend, when i noticed that under my tv there's not enough room to have the wires stick out on either end. so i decided to make a weekend project out of modding the power jack to the same side as the usb port so i can route both cables in the same direction in hopes of saving a bit of space on the left side of the unit.unit in quesiton:long story short i soldered the jack and was hoping to change it to a different style...from thisto thisi like the idea of having a screw on jack, i guess my question is if there is anything im missing or can i just swap the 3pin jack that is originally there (has a V+ and 2 grounds i looked around on the internet and found that info so if its wrong please dont hesitate to correct me.) with the new 2pin screw in jack.thanks in advance!

author: michaeliv
author_rank: Frequent Contributor
timestamp: April 17, 2016, 06:47:51 am
content: Yes it should work.However don't trust the info that you found online about the jack, it might be about a slightly different model.Test the jack connections by yourself.Make sure the + and - are ending up exactly where you want them to end up, avoid creating a short or powering the hub with reverse polarity.
Original Fluke 87 (1A) Fuses - Page 1
Forum section: electronics / beginners

author: osteichthyes
author_rank: Contributor
timestamp: March 15, 2019, 02:36:23 am
content: Is there any reason that I can't use the newer 440mA and 11A fuses in place of the 1A and 15A fuses in a fluke 87 and 27? I know protection wise it's fine, but I'm sure the internal resistances are slightly different, will that make the reading inaccurate?
Original Hakko tips seller recommendation - Page 1
Forum section: electronics / beginners

author: grevan
author_rank: Contributor
timestamp: December 19, 2016, 12:25:35 pm
content: Hi guys,does anybody recommend a trusted original Hakko tips seller on eBay, or elsewhere?I´m looking for tips for the FX-888D station.Thank you.

author: stj
author_rank: Super Contributor
timestamp: December 19, 2016, 07:17:50 pm
content: your looking for T18 series tips.AFAIK there are no T18 clones.

author: grevan
author_rank: Contributor
timestamp: December 19, 2016, 07:41:41 pm
content: No clones, really?I´ve seen so much difference in price, that i could only guess some were fake.

author: stj
author_rank: Super Contributor
timestamp: December 19, 2016, 10:33:02 pm
content: well 900m series tips will fit - but not perfectly.

author: grevan
author_rank: Contributor
timestamp: December 20, 2016, 12:19:53 pm
content: mmm, i noticed that too, the 900m series seem to be the previous one.

author: stj
author_rank: Super Contributor
timestamp: December 20, 2016, 01:26:31 pm
content: bookmark this link - it's very usefull.http://www.hakko.com/english/tip_selection/series.html

author: grevan
author_rank: Contributor
timestamp: December 20, 2016, 06:11:00 pm
content: Thanks stj!
Original PS1 Screen Issue and Modchip? - Page 1
Forum section: electronics / beginners

author: k2Rob
author_rank: Newbie
timestamp: July 08, 2023, 11:38:22 pm
content: Howdy,I recently got hold of a Playstation 1 model SCPH-9002 which has display issuesWhen it's turned it does play the startup sound however all you get of a image is what I've shown in the picture.I've removed the caps on the AV side and they had leaked so I've ordered replacements.Didn't these things have 2mb of memory? This thing has an 8mb chip that sadly has one of the legs broken off. (Model of the chip is km4132g271bq-10)Also there's this crazy wiring going on, is this a modchip of some kind?

author: Shonky
author_rank: Frequent Contributor
timestamp: July 09, 2023, 05:15:04 am
content: Yes that will be a modchip. Possibly a PIC 12C508 or similar.
Original Xbox Replacement VRM Capacitors & Other Questions - Page 1
Forum section: electronics / beginners

author: Nuckenfutz
author_rank: Newbie
timestamp: April 10, 2023, 06:03:33 am
content: Hey guys, new member. Experienced at soldering/some BGA and repaired some 32+ electronics (I'm sure that's nothing special around here). I started all of this around 15 months ago so I'm still learning and have gaps in my knowledge.I had a question about replacing ultra low impedance caps and other caps in general.1. When replacing 3300uf 6.3v (Nichicon Hm series) with an impedance of about 9 mOhms, is it suitable going with Nichicon UHW at 17 mOhm and closely matched ripple handling? Or Panasonic FR at 18 mOhms and fair ripple handling?2. I've heard that when replacing electrolytics with polymers, you're supposed to cut the capacitance to 1/2 or 1/3 depending. Does this remain true for ultra low impedance electrolytics as well, or should you keep the capacitance the same due to both being high end caps?3. I'm attempting to put together a list of suitable replacement caps for 5 versions of disc drives. I had great success with a proof of concept test run. Inappropriate dimension caps. However, most SMD caps I can't identify the manufacturer/series. To me, they appear as polymers due to not having any visible vent - even under the microscope. Do some electrolytics not have vents? One particular example being a SMD 220uf 6.3v. Or could they be hybrids?Finding suitable replacements for the disc drives has been quite a nuisance due to treading territory where few or none have gone before as well as the form factor of some caps (6mm seated height). Would like to open up my options outside of electrolytics.
ORing +5V from two USB hosts - Page 1
Forum section: electronics / beginners

author: rea5245
author_rank: Frequent Contributor
timestamp: November 14, 2012, 07:14:49 pm
content: Hi,I have two USB hosts, a PC and a Sony Blu-Ray player. When either one is on, I want the +5V from its USB port to trip a solid state relay to provide power to my plasma TV (which would otherwise be a monstrous energy vampire).My first thought is to have diodes on the +5V wires, then tie them together at the SSR. The ground wires would be tied together directly. But I'm worried whether I need to isolate the grounds from each other (and whether the diodes sufficiently isolate the +5V lines from each other).If I do need to isolate them further, how would I go about it? I can imagine a solution with two SSRs in parallel. I can also imagine two low-power relays in parallel that turn on an independent 5V supply that then turns on the SSR. But both of those solutions seem like overkill and I'm hoping for something simpler.Thanks,Bob

author: SeanB
author_rank: Super Contributor
timestamp: November 14, 2012, 07:26:44 pm
content: Use the 2 diodes and common the ground and the USB shield wires. They are both connected together ground wise through the TV set.

author: hlavac
author_rank: Frequent Contributor
timestamp: November 14, 2012, 07:31:03 pm
content: USB is usually not isolated, usb ground is usually connected to the case and mains earth.Two diodes will work fine with SSR, don't forget current limiting resistor the SSR control input is usually an IR LED. SSR that switches on zero crossing will be best.

author: rea5245
author_rank: Frequent Contributor
timestamp: November 14, 2012, 07:46:52 pm
content: Thank you SeanB and hlavac.hlavac, I hadn't thought about the limiting resistor, but I just checked the SSR data sheet and it says the input impedance is 1500 ohms. Looks like I'm OK without a separate resistor. But thank you for pointing it out; it's better to check these things than to be unaware of the issue.- Bob

author: Psi
author_rank: Super Contributor
timestamp: November 14, 2012, 10:28:24 pm
content: 1N5817 is pretty common and has a low vdrop.

author: ptricks
author_rank: Frequent Contributor
timestamp: November 16, 2012, 01:10:58 am
content: Also check that the USB ports are indeed powered off when the pc is off, some pc leave the USB power intact which would mean the relay wouldn't ever turn off.