hybridfree/eevblog-posts huggingface dataset:
7555 PWM wrong behaviour - Page 1
Forum section: electronics / beginners

author: m.m.m
author_rank: Regular Contributor
timestamp: April 18, 2015, 06:19:21 pm
content: Hi, I've made a 7555 pwm generator fromschematic and it worked well on the breadboard but it doesn't work well on the PCB when soldered. when I adjust the potentiometer the fan at first is at full speed and then when the potentiometer is on the half way it's on low speed and when it's on the other end it's again at full speed. what should I do?thanks a lot.

author: Simon
author_rank: Unknown
timestamp: April 18, 2015, 06:27:33 pm
content: check your diodes orientation sounds like they are both the same way round.

author: TerminalJack505
author_rank: Super Contributor
timestamp: April 18, 2015, 06:41:00 pm
content: Check to see if you swapped a couple of the wires on the pot as well.

author: m.m.m
author_rank: Regular Contributor
timestamp: April 19, 2015, 07:12:58 pm
content: no, the diodes are OK and I replaced the potentiometer but no sense.this pic might make sense.thanks

author: Simon
author_rank: Unknown
timestamp: April 19, 2015, 07:21:15 pm
content: Check your bread board very carefully maybe with a multimeter to check that all the tracks that need to be brocken are brocken and that there are no invisible solder bridges.

author: m.m.m
author_rank: Regular Contributor
timestamp: April 20, 2015, 06:56:09 pm
content: I checked the resistance between the two not-moving terminals of the potentiometer (i.e. the resistance of the whole potentiometer) and it was about 6k, but it should be around 80~100kOHM. It's definitely the diodes, and when I pull the potentiometer off it's place in the circuit it's resistance gets back to normal. And the resistance around the variable terminal of the potentiometer is about 20k when the knob is at the middle and around 10 ohms when it's on the ends of the potentiometer (even in the other end of the potentiometer where it should be around its maximum value).BTW I used 1N5819 diodes (as suggested inthis link)

author: Simon
author_rank: Unknown
timestamp: April 20, 2015, 07:40:46 pm
content: if it's a 100K pot and half way it measures 20K it could be a log one, what is the resistance in the place of the potentiometer, if you think the diodes are affecting the result then reverse the meter probes

author: m.m.m
author_rank: Regular Contributor
timestamp: April 21, 2015, 01:24:13 pm
content: no, it's not log scale, it's 50kOhm when not in circuit when the knob's half way, reversing the probes makes no sense (maybe because there is two diodes in both directions).

author: m.m.m
author_rank: Regular Contributor
timestamp: April 21, 2015, 06:18:40 pm
content: the problem was with the diodes, they were soldered like parallel but the had to be like series.my bad, sorry.
75ohm video signals - Page 1
Forum section: electronics / beginners

author: fabiodl
author_rank: Frequent Contributor
timestamp: November 01, 2020, 04:10:17 pm
content: In this pagehereread for instance the "Sega Genesis 1 / Mega Drive 1 / Master System" session.It reportsand a 10uF – 220uF / 10v (min) – 16v capacitor470 ohm, 1/4 watt resistorI do not see any valid reasoning for this. Video signals are 0.7vpp, and such consoles all work at 5V, it would seems to me 6.3V is already being "way too safe" for the caps.Same story for the csync line resistor. 5^2/470 is the max power, so a 1/16W resistor still seems a conservative choice.Are there some other reasons for which my reasonings are wrong?

author: Doctorandus_P
author_rank: Super Contributor
timestamp: November 01, 2020, 04:38:51 pm
content: I see some references to connectors and plugging into other stuff, and that may have something to do with it.Without schematics or other information you need to read some coffee grinds or dust of your crystal ball to their motivations.(Or ask them).

author: Benta
author_rank: Super Contributor
timestamp: November 01, 2020, 05:39:11 pm
content: Video signals are AC coupled, and you have no idea at all what the DC level difference between two devices is.In fact, 16 V seems too little to me, and normally VCRs and TV sets etc. use two back-to-back electrolytics for bipolar operation.The 0.7 Vpp signal level is irrelevant.

author: fabiodl
author_rank: Frequent Contributor
timestamp: November 02, 2020, 05:38:52 am
content: Quote from: Doctorandus_P on November 01, 2020, 04:38:51 pmSchematics are available, for instance,hereThe output is essentially the outputs of a CXA1145Quote from: Benta on November 01, 2020, 05:39:11 pmThank you, this is probably the culprit! Still, 1/4 w for charging/discharging the cap once still seems pretty beefy.
76.8 KHz quartz oscillator - Page 1
Forum section: electronics / beginners

author: tomeo.gonzales
author_rank: Regular Contributor
timestamp: September 19, 2016, 03:51:22 pm
content: I have an old quartz crystal with the frequency 76.8 KHz.I want to build a simple sinusoidal oscillator with it using MOSFETS (I have some 2N7000 for this project)Please help me with a circuit diagram.I don't find anything useful after searching on Internet.

author: Cerebus
author_rank: Super Contributor
timestamp: September 19, 2016, 04:01:30 pm
content: Search for "Hartley crystal oscillator" or "Colpitts crystal oscillator" and you'll be inundated with stuff to choose from.

author: JPortici
author_rank: Super Contributor
timestamp: September 19, 2016, 05:09:51 pm
content: "crystal oscillator circuit" will point you to an app note by jim williams

author: edavid
author_rank: Super Contributor
timestamp: September 19, 2016, 05:24:09 pm
content: Quote from: tomeo.gonzales on September 19, 2016, 03:51:22 pmIf it's actually an old crystal, in a large, flat metal can, look for 100kHz crystal oscillator schematics - close enough.(If instead it's a tiny cylinder, look for 32kHz schematics instead.)You will find some circuits using bipolar transistors... they can be adapted to 2N7000s... you may need to adjust the biasing. It's probably better just to buy some bipolar transistors though.There is no such thing as a "simple sinusoidal oscillator". To get a good sine wave, you need AGC, which is not really simple.As a compromise, you can take the oscillator output from the output side of the crystal (usually using an emitter/source follower so as not to load it). That waveform is filtered by the crystal, so it is close to a sine wave.

author: tomeo.gonzales
author_rank: Regular Contributor
timestamp: September 19, 2016, 08:49:04 pm
content: Quote from: edavid on September 19, 2016, 05:24:09 pmThank you edavid. Its a crystal made in 1968 in the former Soviet Union. Build in a glass enclosure like a vacuum tube with the quartz visible. I want to use it for the nice retro look. I found a simple circuit with JFET 2N5484 designed for 100Khz.
7805 regulator related Question - Page 1
Forum section: electronics / beginners

author: khatus
author_rank: Regular Contributor
timestamp: January 22, 2019, 03:03:24 pm
content: This is the datasheet of 7805 voltage regulator produced by "Continental Device India Limited"My question is1. What is Load Regulation(REGL)2. What is Dropout Voltage??I know it's 2V But i want to know it's definition?3. What is Quiescent Current and4. Quiescent Current Change5. Why peak output current is greater than Short Circuit Output Current?? The Short Circuit Output Current should be > peak output current since at short circuit resistance is zero and maximum current will flow??

author: iMo
author_rank: Super Contributor
timestamp: January 22, 2019, 03:27:12 pm
content: 1. What is Load Regulation(REGL)It is a change of output voltage (delta_Vout) when changing the output current (delta_Iout)2. What is Dropout Voltage??I know it's 2V But i want to know it's definition?It is a minimal difference between the Vinput and Voutput such the regulator works reliably3. What is Quiescent Current andIt is the current flowing off the regulator's GND pin (ie. to ground or elsewhere)4. Quiescent Current ChangeIs how the QCurr changes (delta_Iqc) when input voltage or output current changes by an amount.5. Why peak output current is greater than Short Circuit Output Current?? The Short Circuit Output Current should be > peak output current since at short circuit resistance is zero and maximum current will flow??Because the internal protection electronics needs some time to react accordingly (ie current limiting, temperature sensor).

author: mvs
author_rank: Frequent Contributor
timestamp: January 22, 2019, 03:38:52 pm
content: Quote from: khatus on January 22, 2019, 03:03:24 pm1.-3.https://en.wikipedia.org/wiki/Voltage_regulator#Regulator_specification4. Max change of quiescent current over specified junction temperature, input voltage and load current ranges.5. This Vreg has built in short circuit current limiting protection.

author: Wolfgang
author_rank: Super Contributor
timestamp: January 23, 2019, 09:18:19 pm
content: You need to understand some electronics theory to get the meaning of datasheet values.My recommendation: Art of Electronics by Horowitz and Hill.

author: khatus
author_rank: Regular Contributor
timestamp: February 01, 2019, 03:59:52 pm
content: So at the time of theoretical calculation Which value(The peak value of current or short circuit output current) should i take as maximum output current??

author: metrologist
author_rank: Super Contributor
timestamp: February 01, 2019, 04:40:26 pm
content: short circuit is a protection mode so limits the current. Use 2.2A as max possible output.
7812 regulator question - Page 1
Forum section: electronics / beginners

author: Chris Wilson
author_rank: Super Contributor
timestamp: August 13, 2015, 03:44:08 pm
content: I have a circuit where the CMOS and other bits and bobs run off a 15V DC supply feeding a 7812 regulator. The 15 or so volts DC comes off a winding on a toroidal 240V AC transformer, and a full wave bridge. This transformer also supplies a 100 V DC circuit via a full wave bridge and smoothing. I want to run the transformer off a Variac, to make the device, an RF amp, give less power by reducing the 100 V DC. But reducing the 100V DC down low enough to reduce the power sufficiently means the 15 V drops low enough so it will not drive the 7812. What will happen if I feed the low voltage circuits from another regulated DC supply, so the 7812 is effectively back fed, tapping in *after* the 7812? Will it damage anything? If I put a hefty diode after the output of the 7812, would that work, if the circuit doesn't mind the forward voltage drop of the diode? I would like to put a DC in socket on the amp to enable me to test on low power, feeding the low voltage stuff remotely, when required.Need to see the circuit? it's attached, many thanks.Thanks. I know i could just try it, but the 7812 is pretty buried and replacing it is not trivial.

author: unitedatoms
author_rank: Frequent Contributor
timestamp: August 13, 2015, 03:54:08 pm
content: If freqdoubler has low output impedance, has no DC blocking cap, and is powered independently, and timing of powering up powering down is not simultaneous, then CMOS ICs will have their embedded diodes fried.Say, you have freqdoubler AC signal +/-1V. The ICs are unpowered, yet to be powered in few msec, effectively their inputs are still at ground potential. The diodes inside ICs will work like a short to filtering cap, the voltage starts to ramp slowly being rectified, the ICs will heat and may fail.

author: edavid
author_rank: Super Contributor
timestamp: August 13, 2015, 04:01:26 pm
content: No, you can't apply voltage to the output of an unpowered 7812. Diode or-ing should work OK.

author: Chris Wilson
author_rank: Super Contributor
timestamp: August 15, 2015, 06:23:11 pm
content: OK, understood. Thank you both for the replies, appreciated, have a good weekend!
7812 stuck on 0.7V - Page 1
Forum section: electronics / beginners

author: kamtar
author_rank: Regular Contributor
timestamp: May 06, 2020, 03:24:58 am
content: Hello,I have a problem which occurs like once a few days, when I'm switching my board on, sometimes happens that my 12V power rail is stuck on 0.7VI have 12V and -12V rails regulated by 7812 and 7912 from 23V. -12V rail is okay, the problem happens only on the 12V. To solve it I just need to switch it off and on a few times.Everything is properly decoupled and I have 100uF tantalum bulk caps.The regulator isn't heating up and my PTC fuse isn't tripping.When the 12V rail is running on 12V it's perfectly fine and clean.I didn't have the chance to look with an oscilloscope when it's stuck on those 0.7V yet.My question would be can you tell something from that peculiar value of 0.7V?It's possible it's due to some inrush current?I'm not sharing schematics at this moment, I'm mainly curious if you can deduce something specific from that behavior.

author: Jwillis
author_rank: Super Contributor
timestamp: May 06, 2020, 03:35:43 am
content: 0.7V is a typical forward voltage of a diode.

author: Mp3
author_rank: Frequent Contributor
timestamp: May 06, 2020, 12:24:35 pm
content: Is there a voltage divider somewhere before the regulator? Is it the proper resistance still?

author: TimFox
author_rank: Super Contributor
timestamp: May 06, 2020, 01:31:27 pm
content: Re latch-up:Latch-up occurs in ICs when any pin goes negative with respect to the most-negative rail on the device, which is the substrate, by at least a P-N voltage drop. (Similarly for positive excess.) If there is a path between the negative supply (7912 output) and the 7812 output, and the negative power supply comes on before the positive supply, the 7812 output can go negative and cause the latch-up. Before the 7812 powers up, the output impedance is high, and it does not take much current to take the pin negative. The usual cure for this type of latch-up is to put a Schottky diode (with less voltage drop) across the relevant pins (reverse biased), to prevent the parasitic SCR from turning on. In this case, put the diode from the 7812 output to ground. Latch-up may destroy a device if the current supplying the input is sufficient to exceed its power rating, but if there be insufficient current available, the device may survive until the power is cycled.

author: kamtar
author_rank: Regular Contributor
timestamp: May 07, 2020, 01:47:00 pm
content: Thanks, I will try out Schottky on the output.

author: David Hess
author_rank: Super Contributor
timestamp: May 08, 2020, 02:54:50 am
content: If the schottky diode across the output does not solve the problem, then there is another possibility.When power is first applied, if the load on the regulated positive supply is great enough at low output voltage, like with current drawn to a negative supply, then the regulator may latch off due to foldback current limiting and a high input to output voltage difference.This really should not be happening with an input supply voltage of only 23 volts but it might if the regulator was a counterfeit.
78xx capacitors.... WHY? - Page 1
Forum section: electronics / beginners

author: ironduh
author_rank: Newbie
timestamp: May 03, 2014, 05:41:27 am
content: could anyone explain with detail the purpose of the input and output capacitors of the 7805 voltage regulator? I mean, why the input cap must be ceramic and the output should be a ceramic in parallel with an electrolytic, being this ceramic around some nF and the electrolytic around some uF. Almost all the explanations i could find online are just "to improve stabilty" or "to improve the transient response" but they don't explain anything beyond that.examples:http://savedonthe.net/image/1593/7805.png

author: mariush
author_rank: Super Contributor
timestamp: May 03, 2014, 06:13:16 am
content: The ceramic capacitors are DECOUPLING capacitors. You'll find plenty of videos about them just by searching youtube for the term, or Google for articles and so on.Here's a very good example:They have to be ceramic because electrolytic capacitors have poor characteristics for decoupling, they're more suited for bulk storage of energy (to store a lot). The electrolytic in the 7805 circuit is actually optional but it's a good idea to use a small one.

author: ironduh
author_rank: Newbie
timestamp: May 03, 2014, 06:14:10 am
content: thanks a lot man!

author: sleemanj
author_rank: Super Contributor
timestamp: May 03, 2014, 06:15:54 am
content: Quote from: ironduh on May 03, 2014, 05:41:27 amA capacitor (in this configuration) smooths the input and output voltages.A ceramic capacitor has low ESR but also low capacity, however it reacts fast (because of the low ESR).An electrolytic is the opposite, comparatively high ESR, high capacity, however reacts slow (because of the high ESR).Without the capacitors, noise on the input and current draw fluctuations in the demand on the output can both cause poor regulation.In simplified terms, the capacitors react faster than the regulator and fill in the gaps while the regulator catches up with the demands.
8 bit Alu - Page 1
Forum section: electronics / beginners

author: Andy56
author_rank: Newbie
timestamp: July 09, 2022, 08:38:15 am
content: Hi guys. I got a Problem. I dont know what i am doing wrong. The controlline "011" is B+=1. So if i make B=3 my output should be 4. I need help.

author: Andy56
author_rank: Newbie
timestamp: July 09, 2022, 09:09:42 am
content: Ok, i solved that problem.

author: jpanhalt
author_rank: Super Contributor
timestamp: July 09, 2022, 09:20:02 am
content: OK, so what did you do? Did you really get d.4 (b 100) or d.8 (b 1000) as shown?
8-mode christmas controller - Page 1
Forum section: electronics / beginners

author: sdancer75
author_rank: Frequent Contributor
timestamp: January 20, 2020, 05:38:15 pm
content: Hi,I have a Christmas controller like the one attached (PCB marked PD-4F1-A). It seems that it uses a similar schematics like the one I also attached.My question (maybe stupid one) is that LED's in series are connected directly to 230VDC (after the bridge without any voltage step down circuit) which is too high for a led that normally works ~4V.So where am I wrong here?Regards,
8 volts AC to DC hack - Page 1
Forum section: electronics / beginners

author: J4e8a16n
author_rank: Regular Contributor
timestamp: January 09, 2014, 09:06:06 pm
content: Hi,Is it pössible to do something like that?JP

author: Dave
author_rank: Super Contributor
timestamp: January 09, 2014, 10:03:54 pm
content: I'm confused. What exactly are you trying to accomplish here?

author: filip_cro
author_rank: Regular Contributor
timestamp: January 09, 2014, 10:10:52 pm
content: Are you trying to connect this into the mains?AND redraw schematic !!!!!!!!!!!! You need 5 minutes just to figure out will rectifier work. It's totally unreadable.

author: Matt_Heilman
author_rank: Newbie
timestamp: January 09, 2014, 10:24:31 pm
content: The peak inverse voltage of an LED is 5V, so you probably want to place that after the bridge rectifier.

author: TerminalJack505
author_rank: Super Contributor
timestamp: January 09, 2014, 10:40:23 pm
content: It looks like you're trying to implement acapacitive power supply. If that's what you're really trying to do then--now that you know the name of the design pattern--you can do some more research. I've never played with that particular circuit since I like to avoid mains voltages so I can't really give you any further advice.

author: filip_cro
author_rank: Regular Contributor
timestamp: January 09, 2014, 10:57:42 pm
content: Quote from: TerminalJack505 on January 09, 2014, 10:40:23 pmProbably, but he did everything wrong. For example rectifier after LE diode, 120 peak voltage (should be 120 * sqrt(2) ) ...

author: J4e8a16n
author_rank: Regular Contributor
timestamp: January 09, 2014, 11:54:27 pm
content: Quote from: TerminalJack505 on January 09, 2014, 10:40:23 pmThanks

author: Psi
author_rank: Super Contributor
timestamp: January 10, 2014, 02:24:10 am
content: If making a capacitive powersupply for the first time i highly recommend you use one of the designs that has the output negative at earth potential and not floating.

author: digsys
author_rank: Unknown
timestamp: January 10, 2014, 03:20:39 am
content: Quote from: PsiFrom the Wiki - ADD a C1//R2 in series with R1 as well !! Having a "hard ground" may trigger earth leakage, so usually people puta 1M // 0.1uF from -ve to fake GND. NEVER tie it to REAL GND, as it is not isolated from the mains.

author: J4e8a16n
author_rank: Regular Contributor
timestamp: January 10, 2014, 12:41:27 pm
content: You mean that circuit?

author: digsys
author_rank: Unknown
timestamp: January 10, 2014, 10:12:07 pm
content: Quote from: J4e8a16nYup. Having a capacitor on both A/N means that IF you ever plug into an incorrectly wired point, you won't get FRIED.BUT, remember, it is still referenced to mains, so 0V is not a safety point ie I wouldn't have it exposed.IF there is ANY chance of touching the OP, I'd add a 2nd protection device, either a say 18VAC MOV on the AC side of the bridge,or a say 18VDC Transorb on the DC side of the bridge. If the secondary goes O/C, then you have the full AC on the OP.
8 YO Logitech wireless mouse stays powered on despite physical switch in off - Page 1
Forum section: electronics / beginners

author: jimmyc_
author_rank: Contributor
timestamp: March 08, 2024, 09:12:19 am
content: Hello chaps,Back with a question - I have a 8 YO Logitech mouse that stays powered on even when the physical switch is in off mode. What are the possible issues and how should i go about diagnosing it? I would prefer to get some technical background before opening the mouse (I am still using it for work).Also, the 1 x AA battery dies off pretty easily these days. It used to be couple months before I have to change batteries but now, I've got to change batteries every 5 days.jim

author: Minerva
author_rank: Newbie
timestamp: March 08, 2024, 10:24:57 am
content: Could be as simple as the external switch slider cover having cracked. You can try moving the internal switch directly and see if it shuts off.If you're hesitant to work on it though, the best solution may be simply removing the battery when not in use.

author: rsjsouza
author_rank: Super Contributor
timestamp: March 08, 2024, 10:24:58 am
content: When something is crossing a physical barrier such as a mechanical switch, always consider that something is crossing this barrier - either the switch or its surroundings are contaminated with a substance that conducts electricity or the internal contacts of the switch itself might have been displaced and keep a constant contact.Given you mentioned an increase in battery consumption, I think the first scenario is more probable.You have no option other than opening the mouse.Good luck in your repair

author: wraper
author_rank: Unknown
timestamp: March 08, 2024, 11:23:56 am
content: Could be as simple as faulty switch. I had a weird failure in one device that was draining batteries at 1mA when off despite having a physical switch. Turned out the issue was with 3 pin miniature slider switch, the same type I've seen in Logitech mice. I don't recall for sure what the issue was, but I think sliding contact was making a contact with metal shell.

author: jimmyc_
author_rank: Contributor
timestamp: March 08, 2024, 11:26:58 am
content: Thank you all for your time and kind comments. I will open up look into the mouse innards.Have a Great Friday ahead!
850 ohms between switching regulator output and 5V? - Page 1
Forum section: electronics / beginners

author: soFPG
author_rank: Frequent Contributor
timestamp: June 11, 2021, 07:54:59 pm
content: Hello,I was just fitting components onto my board and during a short circuit test my multimeter noticed a connection with 850 Ohms between 1.2V and 5V.I only had a 3.3V LDO and a 1.2V switching regulator with passives soldered so I was wondering whether this is ordinary behavior for a switching regulator?This is the schematic I am working with:

author: viperidae
author_rank: Frequent Contributor
timestamp: June 11, 2021, 08:08:22 pm
content: Is it the same if you swap the meter polarity? There will be a reverse biased diode between vin and out, either for ESD or the body diode if it's switching MOSFET

author: Manul
author_rank: Super Contributor
timestamp: June 11, 2021, 10:04:18 pm
content: Hard to say. What sometimes happens is that low voltage coming from multimeter is enough to turn on low Vgs(th) mosfets. This phenomena migh be mistaken as a short or some resistance. You may try to short the 5V input and repeat the test. Or maybe short 1V2 and repeat test. Could be some small voltage buildup which causes something in an IC to conduct.

author: ocset
author_rank: Super Contributor
timestamp: June 11, 2021, 11:56:48 pm
content: jw5033shttp://www.bmsemi.com/upload/file/20160317/14582062915395185.pdf..with no vin you metered from 1v2 node to vin node and you saw 850R?....sounds ok as your meter could have "woken up" various things inside the chip, and given your 850R reading. I hope you didnt have the 5v on when you used the ohm-meter though.

author: bobbydazzler
author_rank: Regular Contributor
timestamp: June 12, 2021, 12:24:34 am
content: I've measured similar level of resistance between linear regulator pins(I think between output and ground). Checked the schematic and saw around 3 parallel resistors connecting these pins.

author: soFPG
author_rank: Frequent Contributor
timestamp: June 12, 2021, 01:53:05 pm
content: Yes you guys were right. "Shortage" disappeared if I reverse the polarity. Thank you!
852d Replacement Iron Handles - Page 1
Forum section: electronics / beginners

author: SkrillBill
author_rank: Regular Contributor
timestamp: December 06, 2017, 10:22:34 pm
content: I've had a 2-in-1 hot air rework and soldering station for a while now (https://www.amazon.com/dp/B01N55FC6T/ref=sspa_dk_detail_3?psc=1&pd_rd_i=B01N55FC6T&pd_rd_wg=CuX9d&pd_rd_r=669E7YKBC08J9CD5BRZ1&pd_rd_w=NrLi9']this one specifically ). The handle of the iron is starting to break; the threats that hold the metal tip to the rest of the handle. It uses a barrel style connector to connect to the station. Is there a certain brand or handle that is better than others, or will the generic handle for that station work fine?

author: Terry01
author_rank: Frequent Contributor
timestamp: December 07, 2017, 12:01:45 am
content: I have one of those too,same problem. Not a bad wee unit otherwise but the iron does suck ar5e! I have genuine Hakko tips for mine and it solders great,holds heat even when doing bigger stuff. The proper tips have made a difference but maybe that's whats helped in the downfall of my junk iron handle. It heats the plastic bit up after I've been using it a while and I keep needing to stop and tighten the handle to the iron again. I'm on the lookout for a decent iron too. You have to watch how the plug that connects to the unit is wired up. Maybe someone more knowledgable than me can elaborate it a bit more.I'll let you know if I find anything suitable.

author: SkrillBill
author_rank: Regular Contributor
timestamp: December 07, 2017, 12:35:47 am
content: Quote from: Terry01 on December 07, 2017, 12:01:45 amThats exactly what happens. After having it on for a bit I have to stop and tighten it. Really annoying. But I haven't considered proper tips.. Im just using the ones that came with it. I'll have to pick up some hakkos. Thanks for info tho, glad to know it isn't just me.

author: saike
author_rank: Regular Contributor
timestamp: December 07, 2017, 07:56:04 am
content: I got 4 new irons for the 852d off Ebay for $6 each but beware, I have another solder station which uses the same iron body with the same connector but they are wired differently. Plug them into the 852 and the transformer output windings are short circuited

author: Terry01
author_rank: Frequent Contributor
timestamp: December 07, 2017, 08:54:46 am
content: Quote from: saike on December 07, 2017, 07:56:04 amYup,can't remember where I came across the info but that's exactly what I'm talking about. I have looked for better irons to use with the unit but not found anything yet. Even if I find a better iron with the same plug it's well worth making double sure it can be plugged into the unit.I do like the unit but may end up buying something else completely.I suppose it proves you get what you pay forThere are some nice 2nd hand units on eBay for not too much. I may get one and keep this unit as a back up or whatever.
852Dplus Nozzles - Page 1
Forum section: electronics / beginners

author: bostonman
author_rank: Super Contributor
timestamp: June 01, 2021, 02:55:33 am
content: Has anyone purchased nozzles for the 852Dplus hot air pencil?I'm looking to replace an Agilent hybrid chip (see attached) and looking to get a square nozzle, however, the few I've found are expensive.Does anyone know a good place to get these?

author: knapik
author_rank: Regular Contributor
timestamp: June 01, 2021, 06:07:00 am
content: Any specific need for a square nozzle? I would expect just a large circular one to be good enough for the job.

author: bostonman
author_rank: Super Contributor
timestamp: June 01, 2021, 01:26:18 pm
content: I assumed a square one would apply heat evenly.You're correct, a large round one would work too, but I'm uncertain if you mean to use the smaller circular that came with it or buy a large one that would fit around the square IC.If you mean buy a large circular to fit around the square IC, then I'd imagine buying a square would be ideal.

author: RayRay
author_rank: Frequent Contributor
timestamp: June 03, 2021, 01:25:36 pm
content: Aliexpress:https://www.aliexpress.com/item/32915193874.htmlhttps://www.aliexpress.com/item/32950510066.htmlhttps://www.aliexpress.com/item/1005002747984903.html
8846A Fluke DMM has a proplem with the reading and it shows as bellow  - Page 1
Forum section: electronics / beginners

author: Gen.Eng
author_rank: Newbie
timestamp: November 30, 2024, 12:44:02 pm
content: 8846A Fluke DMM has a proplem with the reading and it shows as bellowThe Reading of the applied value on the range adds to half the applied value + the readings in the above tabelsVoltage DC Open Loop ValueRange Unite Reading Uint100 mV OL mV1 V 0.128 V10 V 0.128 V100 V 4.08 V1000 V 3.95 VCurrent DC Open Loop ValueRange Unite Reading Uint100 µA OL µA1 mA 0.41 mA10 mA OL mA100 mA 41.5 mA400 mA 41.5 mA1 A OL A3 A OL A10 A 4.22 AResistance Short Loop ValueRange Unite Reading Uint10 Ω 8.08 Ω100 Ω 40.73 Ω1 KΩ 0.0406 KΩ10 KΩ 0.0406 KΩ100 KΩ 4.04 KΩ1 MΩ 0.0039 MΩ10 MΩ 0.039 MΩ100 MΩ 0.039 MΩ1 GΩ 0.039 GΩThe Reading of the applied value on the range adds to half the applied value + the readings in the above tabelsFor Example at range 10 ohm the value show up 8.08 if we applied 1 ohm it will equal (8.08 + (applied Value /2)) and it shows 8.58 ohmFor Example at range 100 ohm the value show up 40.73 if we applied 100 ohm it will equal (40.73 + (applied Value /2)) and it shows 90.73 ohmFor Example at range 100mA the value show up 41.5 if we applied 10 mA it will equal (41.5 + (applied Value /2)) and it shows 46.5 mAVoltage AC Open Loop ValueRange Unite Reading Uint100 mV 7.3 mV1 V 0.0072 V10 V 0.0072 V100 V 0.0475 V1000 V 0.638 VCurrent AC Open Loop ValueRange Unite Reading Uint100 µA 0.09 µA1 mA 0.0006 mA10 mA 0.005 mA100 mA 0.06 mA400 mA 0.575 mA1 A 0.00087 A3 A 0.0057 A10 A 0.0062 A

author: coromonadalix
author_rank: Super Contributor
timestamp: December 03, 2024, 03:10:29 am
content: don't double post it pisses of peopleyou are in the repair thread already
898d+ soldering station help - Page 1
Forum section: electronics / beginners

author: Asjimenez51”
author_rank: Newbie
timestamp: February 13, 2021, 05:08:33 am
content: So I posted here a year ago I accidentally pulled out the wires I was looking for a wiring diagram well I figured that out thanks to help from herebut now, the ceramic piece that’s connected to the heating circuit board has disconnected and How do I glue it back to the piece? It gets too hot and falls right back off… I purchased three different solder iron handles and they all immediately get super hot turn cherry bright red and burn the crap out of the tip and the base.There’s a fuse dial on the back of my soldering station I did mess with it I don’t know what that is though.Yes I am an extreme noobPlease help

author: bob91343
author_rank: Super Contributor
timestamp: February 13, 2021, 05:58:33 am
content: It's the Humpty Dumpty syndrome. I certainly wouldn't be able to fix that. Bite the bullet and buy a new one. Just my opinion.
93LC46/56/66 Serial EEPROM - A Few questions. - Page 1
Forum section: electronics / beginners

author: erikhedb
author_rank: Newbie
timestamp: February 01, 2015, 06:43:47 pm
content: Im trying to dump the content of a salvaged ATC 93LC46 Chip. The 93LCXX chip seams to be very common and also made by many different manufacturers.http://pdf.datasheetcatalog.com/datasheet/Ceramate/mXruxvr.pdfHave done a few Arduino and AVR projects but cant get a grip ion this chip.I do know that I must shift out bits with commands and then shift in bits to read the EEPROM.byte READ = 0b110; //read instructionbyte WRITE = 0b101; //write instructionetcIn order to read I must shift out the read instruction together with the adress to read. After that shift in the data in that adress.The data sheet specifies:START BIT 1READ 10ADDRESS A5 A4 A3 A2 A1 A0DATA D15 - D0 25So what do I shift out to get something in?How do I specify the different adressess?A0 = 160 = 10100000A1 = 161 = 10100001Also, how are the memory organized. A0-A5 is just six differend values.Can someone please point me in the right direction?/ErikMore, its a petty the timing diagrams are so short, a full low-high sequence would explain it all.Also, is this a SPI device? I suspect it might be.

author: elgonzo
author_rank: Unknown
timestamp: February 01, 2015, 06:51:12 pm
content: Quote from: erikhedb on February 01, 2015, 06:43:47 pmSeems you have a misunderstanding. A0 ... A5 are address bits. Thus, you have 6 address bits, giving an address range of 0...63.Also, read the datasheet carefully, especially about timing and necessary clock impulses. It might be that only 6 address bits are used by this chip but the protocol still demanding 8 (or less/more) clock impulses as if there were 8 address bits...

author: erikhedb
author_rank: Newbie
timestamp: February 01, 2015, 07:11:51 pm
content: Ah,So A0 is address bit 0 etc.So: 000000 is the start address and 111111 is the end address?Also 1024 / 64 = 16 -> Shift in D15-D0 ie data bit 0 to Data bit 15.Thanks

author: elgonzo
author_rank: Unknown
timestamp: February 01, 2015, 07:14:53 pm
content: Quote from: erikhedb on February 01, 2015, 07:11:51 pmYupp.

author: woodchips
author_rank: Frequent Contributor
timestamp: February 02, 2015, 05:39:35 pm
content: Don't know which manufacturer you have, but these chips can work in 8 or 16 bit mode. And some will only work either in 8 or 16 bit mode.
9A761 ic in wireless charger - Page 1
Forum section: electronics / beginners

author: u666sa
author_rank: Frequent Contributor
timestamp: April 05, 2025, 12:07:07 am
content: I have this desk which has a wireless charger inside of it. It feeds via 12 volts. When 12 volts is connected to charger iPhone detects it, charger for a few seconds, on charger red LED flashes, and then iPhone uses charge.However, if I lower the voltage of 5V, LED on charger is solid green and iPhone charges just fine.Just trying to figure out how to make it work here, either lower the voltage to 5V, in which case the charger becomes uselessly slow, or maybe find out what that IC does, it's datasheet and figure something out. Perhaps get a new charger board?I don't know, suggest something.

author: amyk
author_rank: Super Contributor
timestamp: April 06, 2025, 03:13:51 am
content: Pictures please...9Axxx matches AAT2601A if it's a QFN36, otherwise it could be something else.

author: BILLPOD
author_rank: Frequent Contributor
timestamp: April 07, 2025, 12:46:06 pm
content: Good Morning U666sa, Too many unknowns. The status that the LED is indicating is the big one; what color is the LED when the phone is fully charged? The amount of current going into the phone is another one. What happens during any of the voltages between 5 and 12? If the desk has an owners manual would be great, but apparently you don't have one, so look over the circuitry closely and see if any of the components has voltage parameters. Good luck and be sure and report your progress.
9DoF sensor with fusion algorithm - Page 1
Forum section: electronics / beginners

author: Tantalum
author_rank: Regular Contributor
timestamp: January 09, 2025, 12:59:04 pm
content: HelloAre there other 9DoF motion sensors available that integrates a fusion algorithm, like the BNO080/5/6?There are Invensense (TDK) but they seem to have only 6-DoF's.ThanksEdit:Found the ICM-20948, but it's NRND
"9F" marking sot23-5 voltage regulator? - Page 1
Forum section: electronics / beginners

author: flolic
author_rank: Frequent Contributor
timestamp: March 17, 2020, 10:25:34 am
content: Anyone can identify this voltage regulator? It is sot23-5 device with 9F marking.Input voltage is 12V, output voltage is 5V. Chip is used in PS4 game consoles to provide 5V to HDMI connector.Pin 1 should be output enable input, but I am not 100% sure.Looking for part number or equivalent device with the same pinout.

author: Zero999
author_rank: Super Contributor
timestamp: March 17, 2020, 11:03:07 am
content: Why do you think it's the voltage regulator which is faulty?I suspect it's fairly generic. Any regulator rated for >12V in and 5V out and can supply over 50mA will probably do. The challenging bit is finding one in the right package.

author: flolic
author_rank: Frequent Contributor
timestamp: March 17, 2020, 12:34:55 pm
content: No, this one in the picture is just fine. Because I replaced the dead one with the salvaged part.That regulator very often die as a result of lightning, or when someone connect or disconnect HDMI cable while the devices are on.I've replaced many of those, salvaged from the dead boards. But now I am out of those and would like to find adequate part.There are many voltage regulators with the right specifications and wrong pinout, that's the reason for original post.I would like to find a drop in replacement, or hope someone can decipher "9F" marking

author: Mechatrommer
author_rank: Super Contributor
timestamp: March 17, 2020, 12:52:25 pm
content: if you cant find compatible pins in digikey, its time to make a breakout/daughter/deadbug board...https://www.digikey.my/products/en/integrated-circuits-ics/pmic-voltage-regulators-linear/699?k=voltage+regulator&k=&pkeyword=voltage+regulator&sv=0&pv1065=i1&pv1779=249171&pv69=409393&pv1291=405420&sf=1&FV=-8%7C699&quantity=&ColumnSort=0&page=1&pageSize=25
9v power and return signal in the same cable? - Page 1
Forum section: electronics / beginners

author: ramphands
author_rank: Contributor
timestamp: March 08, 2022, 01:51:45 am
content: Hello all!I created a variation of this TI reference electret microphone line-level preamp:https://www.ti.com/lit/ug/tidu765/tidu765.pdf?ts=1644907822477&ref_url=https%253A%252F%252Fwww.ti.com%252Ftool%252FTIPD181Here's my version:I shrank it down to fit on the side of a 9v battery, added a power switch and used 3.5mm jacks to allow the microphone and output to be unplugged.It works fine, but of course it would be preferable to have the microphone as close to the circuit as possible to minimise bad stuff. That led me to start a revision where the mic is soldered directly to the board in a perpendicular fashion, with the board being approximately the same shape as before, albeit narrow enough that the entire mic and electronics could be housed in a 6mm internal diameter bit of steel tubing.My issue with this is of course the 9v power. I'm planning on using two of these microphones to record binaurally, so the cables will be roughly 1m or so in length. Would it be bad to use a multicore shielded cable to both supply the power and take the resulting audio signal? How would grounding work in such a case?Many thanks for any help!

author: james_s
author_rank: Super Contributor
timestamp: March 08, 2022, 02:01:28 am
content: I don't see any problem with this, it's DC from a battery so it shouldn't interfere with anything. A lot of microphones even use phantom power, I've never looked into exactly how that works though.

author: ramphands
author_rank: Contributor
timestamp: March 08, 2022, 03:19:40 am
content: Thanks for the reply!I guess I have to be concerned about voltage drop on the battery, but I was also concerned about whether the -ve lead of the 9v battery should be tied to the cable shield along with the ground from the circuit or should be run on a seperate ground wire. Not really a big deal to add a seperate pad on the pcb and test it both ways, but grounding is still a rather confusing subject for me.

author: Zero999
author_rank: Super Contributor
timestamp: March 08, 2022, 10:18:24 pm
content: There is no benefit to using a separate wire for 0V. Only signal current will flow through the external cable. The drop in battery voltage is a non-issue, as the OPA172 can work down to 4.5V.

author: ramphands
author_rank: Contributor
timestamp: March 11, 2022, 07:21:10 am
content: Thank you very much!
_ _ _ possible 100khz SINE osc for ESR ? _ _ _ - Page 1
Forum section: electronics / beginners

author: 3roomlab
author_rank: Frequent Contributor
timestamp: March 23, 2014, 04:17:49 pm
content: not sure where to post this, but probably somebody have already gotten their head around to this kind of oscillator. i have not used it before, any one tried a oscillator like this before for their ESR? just happened to be diggin around and happened to pop my head in the simulator to try this version.(if you have tried this on a breadboard, do post a pic)

author: SeanB
author_rank: Super Contributor
timestamp: March 23, 2014, 04:32:28 pm
content: Phase shift oscillator. Each section has 60 degrees ( or pretty close) of phase shift and this combined with having enough gain to exceed unity through the loop makes an oscillator. Has poor stability, and is sensitive ( and non linear as well) to both supply voltage, temperature and component aging. Can be difficult to start at times with particular component values, but can be made to work. Do not expect a sine wave out of it unless filtered. Having the capacitors like that makes it very noisy as it amplifies harmonics quite well.
"adaptive" pre-regulator for linear power supply with pass-through - Page 1
Forum section: electronics / beginners

author: exe
author_rank: Unknown
timestamp: January 10, 2016, 10:52:34 am
content: Hi!I'm designing a bench power supply for hobby needs. And I wanted to make it small, efficient and low noise. I found an idea of buck pre-regulator very interesting, but certainly it adds some noise. However, in my applications noise is only of concern for low-power loads. So, a small analog circuit may be sensitive to the noise, but my micro-dril consuming 3A l will be fine. Keeping this in mind, I decided to make the buck regulator "switchable", i.e., it can be disabled under light loads and activated only when the dissipating power is higher than what the heatsink can safely dissipate.So, here it is, please see attachment (Vrect is unstabilized rectifier output, SiZ300DT is mosfet half-bridge, sorry for ugly representation). The idea is that the buck is managed by a MCU PWM signal. When we want to pass through the preregulator we just write "1" into PWM pin and buck's half-bridge is "always on". What do you think about this?There are a few potential issues though. First, high-side mosfet is normally driven by a bootstrap circuit that will not work if there is no switching. I solved this by supplying required driving voltage into the driver (VHI pin on U7). But I've never seen such configuration in any datasheet. Do you think this will work?Second, do I need a snubber(C27 R12)? I saw snubbers shunting bucks' diodes to reduce the noise. So I left one here. But may be I don't need it?I would like to reduce switching noise as much as possible so I chose low frequencies (<100KHz) to drive the buck and slow mosfet switching speed (R5,R7,R20) to make it quieter. But in the datasheet for UCC27223 () there are no gate resistors. Does this mean they are not really helpful? The datasheet only tells about R20 to slow down the high-side mosfet. Does this mean gate resistor R5 is not needed for high-side? And what about low-side?PS forgot to say, input is 15-18V, up to 3A. Output up to 5A, if this all matters.http://www.ti.com/lit/ds/symlink/ucc27223.pdf
"Connect test leads" message on Uni-T multimeter - Page 1
Forum section: electronics / beginners

author: NottheDan
author_rank: Frequent Contributor
timestamp: January 24, 2018, 02:25:09 pm
content: Yesterday I got a second-hand Uni-T UT58C multimeter and the damn thing keeps showing the abovementioned message. And yes, I do have test leads connected and it works. The message is just annoying me.So do I have to go through some secret ritual to make it go away?

author: stj
author_rank: Super Contributor
timestamp: January 24, 2018, 05:58:31 pm
content: maybe it wants you to touch the probes together to zero itself.

author: kasone
author_rank: Contributor
timestamp: January 24, 2018, 06:29:47 pm
content: Here is a link to the user manual:https://www.manualslib.com/manual/538636/Uni-T-Ut58a.html?page=10#manualMaybe this will help.

author: NottheDan
author_rank: Frequent Contributor
timestamp: January 26, 2018, 11:37:27 am
content: Quote from: kasone on January 24, 2018, 06:29:47 pmYeah, seen that but all it does is tell you to plug the test leads into the correct sockets. Which they are.Quote from: stj on January 24, 2018, 05:58:31 pmFirst thing I tried. Unless it expects some naughtier touches that isn't it.

author: Karlo_Moharic
author_rank: Regular Contributor
timestamp: January 26, 2018, 12:05:37 pm
content: Open in up and see if all connections are OK on input jacks. It can easily be a bad connection on one of the split jacks that is causing device to think that leads aren't connected

author: daveshah
author_rank: Unknown
timestamp: January 26, 2018, 11:20:20 pm
content: I'm pretty sure that meter has no actual lead detection, it just displays a static indication based on the mode you're in showing you how to connect the leads - you just have ignore it.
'Dead' pixel remapping for Sony DXC-950 - Page 1
Forum section: electronics / beginners

author: Unknown
author_rank: Unknown
timestamp: November 08, 2009, 11:51:34 pm
content: I'm not 'new' to electronics, but since this is my first post I picked here. I have a Sony DXC-950 camera that has developed several 'dead' pixels. In the camera's menu, there isn't an automatic function for re-mapping dead or 'hot' pixels. Does anyone know if there's a software routine or anything that can be run somehow to identify and re-map these dead spots? I'd assume that since there is a 9-pin serial type connector normally used for RGB out that in some service mode it may be able to be used as an I/O port?? Their documentation of this problem leaves much to be desired and I don't have a service manual for this camera. I set up a couple of JVC industrial cameras at a community college and one of the first routines the installation manual suggested you run was the dead pixel re-mapper, since this is a common problem with CCD's. Any suggestions?Thanks!

author: Simon
author_rank: Unknown
timestamp: December 27, 2009, 10:52:24 am
content: you will have to contact the camera manufacturer. if you want help from forums try camera forums, I've found lots of photographers also have electronic/computer skills too and can handle most of their own maitenece