hybridfree/eevblog-posts huggingface dataset:
Safe then sorry - Page 1
Forum section: electronics / beginners

author: MrZwing
author_rank: Regular Contributor
timestamp: August 30, 2015, 08:57:10 am
content: I have been thinking about buying a air re-flow/ heat gun station specific the one Dave showed off on his Channel a long time ago.But the wall socket thing is the wrong kind but it says it can handle 220V -+10% and the standard where i live is 220–240 V 50 Hz.and maximum voltage it should be able to handle is 242V and the Hz is the corrects one. could I just snip off the wrong plug and mount the one I use here. I'm 99% certain that is the case but when it comes to high voltage I'd rather be 100% certain, especially now when I'm just getting started.

author: cs.dk
author_rank: Unknown
timestamp: August 30, 2015, 09:02:00 am
content: That should work fine.. I've got a Yihua 882D+ i'm quite happy with it.http://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p2050601.m570.l1313.TR0.TRC0.H0.XYihua+882D%2B.TRS0&_nkw=Yihua+882D%2B&_sacat=0

author: MrZwing
author_rank: Regular Contributor
timestamp: August 30, 2015, 09:25:30 am
content: thinking about getting a next pay check.www.aliexpress.com/item/Free-Shipping-ESD-safe-220V-HAKKO-936-HAKKO936-hakko-936-Soldering-Station-with-907-soldering-handle/524720490.htmlheard these Hako clones are quite good and the cheap soldering station i have now is well "ok" so far. it's mostly the hot air station that i need for de-soldering an some SMD work (i love small circuits so SMD is the way to go"

author: MrZwing
author_rank: Regular Contributor
timestamp: August 30, 2015, 09:30:47 am
content: And now a hot-air station is on the way and I'm nerdily excited of all the possibilities.
Safe to test stability of power supply board by shorting output? - Page 1
Forum section: electronics / beginners

author: skillz21
author_rank: Frequent Contributor
timestamp: November 05, 2018, 08:30:41 am
content: I have this:https://ebay.us/7Wb9oMI want to test the stability of this power supply. Since it has built-in current limiting, is it fine for me to simply set a voltage, say 5v, set a current limit of 5 amps, and just short the output and leave it? The website says not to short the output for very long, but since it has current limiting, is it safe? Or will i end up burning the board?

author: Rerouter
author_rank: Super Contributor
timestamp: November 05, 2018, 09:20:26 am
content: My eye is caught by the "0.8V" minimum on the output, It may not like a hard short.Equally full open to a sudden short will be the hardest test you can do on a PSU, until the control loop responds it can have far far more than your 5A set point, this can pop transistors if its not well builtThe fact it says not to short the output for long would back up that 0.8V minimum, it may be that with a hard short it cannot regulate it.

author: skillz21
author_rank: Frequent Contributor
timestamp: November 05, 2018, 09:38:04 am
content: Quote from: Rerouter on November 05, 2018, 09:20:26 amThe one that I bought wasn't that exact web page, it is just the same type. Well, maybe I should have asked first... I did actually try shorting, but at a very low voltage (3v). I took it up to about 3A before I disconnected and decided to ask on here. So I'm guessing you guys recommend I don't do this again? (PSU board it still working properly BTW)Thanks for the help.

author: pelule
author_rank: Frequent Contributor
timestamp: November 05, 2018, 12:14:12 pm
content: QuoteIMHO this is the lowest adjustable stable output voltage, not related to a short (0V).A short creates at the given current limit conditon the maximum power dissipation for the supply.Thus surviving depent on the thermal design mainly.If you like to test the performance on the safe side - short only a short time (pulse generator, ~100ms) and in addition observe the temperature of the gear./PeLuLe

author: David Hess
author_rank: Super Contributor
timestamp: November 06, 2018, 03:50:45 am
content: Just because it has current limiting does not mean it has sufficient thermal protection to drive a continuous short.
Safe to use Lipo battery with this chip ??? - Page 1
Forum section: electronics / beginners

author: eevfan007
author_rank: Contributor
timestamp: May 01, 2014, 12:00:54 pm
content: Hi!Im making a boost converter/charger for my iphone. I found this chip:http://www.ti.com/product/tps61032Is this safe to use with LiPo batteries? And do-able?I read the datasheet, and it seems to be fine. I have also placed a protection diode from the battery up to this chip to be super safe.Thanks

author: digsys
author_rank: Unknown
timestamp: May 01, 2014, 12:38:53 pm
content: It's exactly suitable for all common battery types, as per the specs. DON'T waste a diode drop for "protection",not with a 96% efficient chip !! That's criminal :-) and not necessary. It has UVLO, so all is good.

author: retrolefty
author_rank: Super Contributor
timestamp: May 01, 2014, 02:37:53 pm
content: Note that higher rate chargers to work properly with iphones have to have specific voltages applied to the D+ and D- signal lines via voltage dividers before the phone will except higher rate charge. This was an attempt to discourage 3rd parties charges from working, but was soon figured out. The Adafruit site has details as they were first developing their mintyboost product.
Safe voltage input into Cell phone mic - Page 1
Forum section: electronics / beginners

author: tiofilo75
author_rank: Contributor
timestamp: May 16, 2013, 08:30:27 pm
content: Does anyone know what a safe range is to input to a cell phone's 3.5mm jack? I was thinking less than .5V, what do you all think?

author: SeanB
author_rank: Super Contributor
timestamp: May 16, 2013, 08:45:26 pm
content: You will find the Mic input actually puts out around 1-1.5V as power for the microphone, and shorts that to ground to signal that the pushbutton on the mic is pushed. You need to feed it via a non polarised capacitor of around 220n with a 10k or so value resistor on the phone side to ground, as this will tell it the mic is connected, and the signal will probably be under 100mV peak to peak at most. Often the socket is 4 way as well, with ground as the last position, and mic as the next, with right and left audio being the top ring and tip respectively. you might have to use a cable for the handset ( or a knockoff) and trace the wiring for the mic to feed it the signal.
Safe way to bypass a transistor (temporarily)  - Page 1
Forum section: electronics / beginners

author: Sanxion
author_rank: Contributor
timestamp: December 11, 2023, 01:28:02 pm
content: Hi all,Could anyone explain how I can bypass PST518B in the reset circuit for an Amiga 2000?This may seem like an odd request, so please allow me to explain:I have been building a new motherboard (rev 6.2) and I don't have that transistor, I have ordered it but it may take days to arrive and I am curious if I can temporarily do without it to test the build. The earlier version of the motherboard didn't actually use the transistor so I am hoping it can be bypassed for now until it arrives. I have attached the schematics for both versions of the motherboard.Thanks.

author: shapirus
author_rank: Super Contributor
timestamp: December 11, 2023, 02:08:51 pm
content: It looks like the images were cropped so that the trasistor was left outside. Or maybe I just can't see it :).

author: macboy
author_rank: Super Contributor
timestamp: December 11, 2023, 02:10:56 pm
content: If you mean PST518B, that is not a transistor, it is a reset controller. It can assert the reset line when the +5 V rail is below about 4.4 V. Because of the open-collector output, which is wired-or connected to the '339 open-collector output, you can actually just leave the component out. The rest of the reset circuit will function just like the old version without this.

author: Sanxion
author_rank: Contributor
timestamp: December 11, 2023, 02:25:02 pm
content: Thanks Macboy.What do you mean when you say: It can assert the reset line when the +5V is below about 4.4V?Also, if it can be left out, what is its purpose?

author: Andy Chee
author_rank: Super Contributor
timestamp: December 11, 2023, 02:32:31 pm
content: Look at this diagram.Notice how the voltage is a bit sluggish reaching 3.3V? That slow ramp up/down time could cause unpredictability in your system. The reset controller creates a nice square edge, triggered at about 3.0V (it's not labeled on the diagram, I'm just visually estimating).In your case, the supply voltage is 5V and it will dropout at 4.4V.
Safely discharge stored current - Page 1
Forum section: electronics / beginners

author: fixit7
author_rank: Regular Contributor
timestamp: June 11, 2019, 03:49:45 pm
content: I would like to salvage some parts.I did so many years ago, but had a problem with leftover current.How do I safely discharge any stored current ?http://www.repairfaq.org/sam/crtfaq.htm#crtsdchttps://imgur.com/a/ZTg3dqvThanks.

author: bob91343
author_rank: Super Contributor
timestamp: June 11, 2019, 04:27:09 pm
content: You don't have stored current. Perhaps you are thinking of stored energy in capacitors. You get rid of it by short circuiting the capacitors. Small capacitors rarely store enough energy to cause trouble but larger ones can.When working on gear that uses high voltage, by all means discharge the capacitors. It's also wise in case you are going to connect sensitive test equipment.Sometimes it's as simple as laying a screwdriver blade across the capacitor terminals. Other time you need to be a bit more savvy to avoid various kinds of damage.We all make mistakes but as long as they have no permanent results we can learn from them.

author: fixit7
author_rank: Regular Contributor
timestamp: June 11, 2019, 04:35:41 pm
content: thanks. I just want to pull the boards and salvage the components.That link mentioned using a 5 watt resistor.I will be using gloves and an insulated wire cutter after I have discharged capacitors.

author: Zero999
author_rank: Super Contributor
timestamp: June 11, 2019, 05:00:31 pm
content: Using a resistor is a good idea, because a limits the current and discharges the capacitor in a more controlled manner, rather than producing huge sparks, which can fire out pieces of molten metal and weld whatever it is you're shorting it with to the capacitor.Afterwards, measure the voltage on the capacitor to check it's safe to touch.
safely switching bias resistor built-in transistors in a car - Page 1
Forum section: electronics / beginners

author: erik_m
author_rank: Newbie
timestamp: September 19, 2021, 08:58:15 am
content: In the attached circuit, is it safe to connect the inputs of Q703 and Q726 (near the blue text) directly to the line from ACC as indicated, or should I add resistors and capacitors similar to what is on the ill+ line going to Q713 and Q733? Datasheet for Q703 and Q726:https://www.rohm.com/products/transistors/digital-transistors/standard/dtc114wka-product#productDetailIf you want more background info:I'm trying to replace the stereo in my 2005 Mazda Demio but it shares circuitry with the climate controls. It has a large circuit board with the display and controls attached to the front console which connects to the radio's main pcb which is inside a more normal looking metal case. The main pcb supplies power for the front panel illumination bulbs and climate controls. I've traced the relevant parts of the circuits in both boards (I hope) and it looks like I can cut the radio's LCD display out and remove the controls without affecting the climate controls. I've also traced the power supply circuit in the stereo and plan to build a smaller pcb with just this circuit to power the climate controls. There's a separate smaller pcb that plugs in to front pcb that then controls the rear demister, hazard lights, inside or outside air, and A/C. Here's some photos:https://photos.app.goo.gl/dYFd4N8tFjDKzsRC8
Safety of measuring the circuit powered by switching power supply by osciloscope - Page 1
Forum section: electronics / beginners

author: marekpasek
author_rank: Contributor
timestamp: July 16, 2017, 10:16:52 pm
content: Hi, I have ordered some switching power supplies from china (originally supposed to supply LED strips) and I want to make a power supply from them, but I measured that the ground of the 12v output of the supply has a voltage about 90v referentially to The Ground (meant the ground which the most of oscilloscopes is grounded to) but when shorted with The Ground ,only few hundreds of miliamperes flows (I think it was about 300mA at most). And I have also watched Dave's video called "How to not blow up oscilloscope". There he said that the measured circuit should be isolated from the scope otherwise the scope may blow up, when falsely connected. So I have a question, is it safe to measure circuit connected to the power supply I am gonna make by oscilloscope when attaching the ground aligator clip to the ground of the supply having 90v to The Ground?Thanks a lot (I would like to not blow up my new scope immediately)

author: Zero999
author_rank: Super Contributor
timestamp: July 16, 2017, 10:35:10 pm
content: It's normal for a switched mode power supply to float at around half the mains voltage, due to a tiny current coupled by the Y capacitor which is required to suppress radio frequency interference. However 300mA is far to higher current to measure when it's short circuited to ground.Are you certain you've not made a measurement error? Could you have got the decimal point wrong and it's really 300µA? Connect a small mains voltage incandescent lamp, between the 0V side of output of the switched mode power supply and earth: does it glow dimly?If the answer is no, now try connecting a 100k resistor between the 0V and earth and measuring with your multimeter: is the voltage still 90V or has it dropped to something safer?

author: marekpasek
author_rank: Contributor
timestamp: July 16, 2017, 10:42:53 pm
content: Thanks a lot. I will try what you suggested. Currentwise I am quite sure with 300mA because I have 25-years-old Metex multimeter which I inherited and which has no uA range (but why not to assure myself by checking it).
Safety precautions for homemade USB Lamps Advice Needed - Page 1
Forum section: electronics / beginners

author: electroDart
author_rank: Newbie
timestamp: September 15, 2019, 09:18:39 pm
content: I make USB lamps as a hobby, but I would like to sell them at some point.They are basic parallel series of leds, each LED has its own resistor to bring it to around 20ma max current.I use the chinese dc-dc 0.9-5v boost boards for the battery powered ones.I use an epoxy potted micro usb socket, just the vbus and gnd soldered ( no negotiation ) for the usb powered ones.I want to make the usb lamps as safe as I possibly can, to account for user error. I'm concerned about two things. 1. that someone will connect the lamp to very expensive laptop usb port and it could cause damage. 2. that someone will connect it to a knockoff usb charger which could overvolt it and cause a fire.I already have a set of 500ma self healing fuses ( 1206 from china ), and some other THT ones at 400ma from the UK.Any advice on how to proceed would be greatly appreciated. I did wonder if just connecting the usb 0.9-5v dc-dc board might do the trick as they already seem to contain fuses.Thanks.

author: james_s
author_rank: Super Contributor
timestamp: September 15, 2019, 11:15:52 pm
content: USB ports are already quite safe, they are low voltage and current limited. There is nothing you need to do other than make sure you don't have sharp edges or toxic substances, if you want to add a low current fuse that won't hurt anything but it shouldn't really be necessary.

author: Fredled
author_rank: Newbie
timestamp: September 20, 2019, 09:08:04 pm
content: I would recommend to power your leds at less than 20mA. That way they will be less likely to fail and take too much current.A self ressetable (self healing) fuse is a good, inexpensive solution. But it's necessary only in case of damage to the led light causing a short cicruit. Normal use should never be dangerous for any device.

author: james_s
author_rank: Super Contributor
timestamp: September 20, 2019, 11:35:14 pm
content: You can probably go even cheaper with an ordinary fuse or fusible resistor. If part of the device fails, chances are it will go into the trash. Self resetting fuses are only really useful for devices that connect to external devices that could present a recoverable fault condition.
Safety transformer vs Controll transformer - Page 1
Forum section: electronics / beginners

author: crgarcia
author_rank: Regular Contributor
timestamp: June 11, 2022, 12:44:14 pm
content: I want to automate my house's door. I can wire whatever I want because I have to make the walls new anywaysI decided to use an electric door strike instead of a smart lock with batteries or wires hanging around.I bought this strike, but I did not notice that is 12 VAC and not 12 VDC:https://secure.reichelt.com/ch/en/door-opener-with-memory-function-flush-fitted-extel-5111090319-p275997.htmldatasheet:https://cdn-reichelt.de/documents/datenblatt/E910/EXTEL_5111090319_DB-DE.pdfI want to wire it to a central box, where I will add some "smart relay" that will send the 12VAC pulse to the lock.I started looking at devices that could bring 220VAC to 12VAC and that could be installed in a DIN rail.Is this Control Transformer (whatever that means) a good choice:Comatec TBD2/018.12/P3Besides Voltage and Current, are there other things I should pay attention to?Thanks!

author: rstofer
author_rank: Super Contributor
timestamp: June 11, 2022, 05:09:25 pm
content: Seems reasonable to me as long as the electric strike requires less than 1.5 Amps and it probably does.This would also be a good time to think about an alarm system and you might as well pull CAT 5E cable to as many places as you can afford.WiFi is useful but it is still very slow compared to a wired system. In fact, WiFi is a PITA in a residence of any size. The modem is probably in the front corner of the house and the PCs are about as far away as possible. The WiFi pods work but they bring their own set of problems.https://www.startech.com/en-us/faq/network-cables-ethernet-categorieshttps://www.xfinity.com/learn/internet-service/wifi/xfi-podI would opt for a pair of ethernet jacks at virtually every receptacle location in the house. I might include an outlet for the landline phone at each location. That's pretty easy since the modular wall outlets allow mix-and-match jacks. If I were looking ahead, I would even have a pair of outlets behind the refrigerator. You just know those things are going to be IoT in the near future. Why shouldn't it reorder stuff that has been used up? Or at least offer a web page to allow for ordering.Don't forget to pull an ethernet cable to the general vicinity of your sprinkler timer (if any). Again, BlueTooth and WiFi work but nothing is as reliable as hardwire.https://www.orbitonline.com/products/b-hyve-smart-indoor-outdoor-irrigation-controllerCable to any external building? Cable to a good location for the outdoor WiFi extender?

author: Terry Bites
author_rank: Super Contributor
timestamp: June 11, 2022, 05:12:08 pm
content: Control transformers are used to power control panels. Say, inside a machine tool or some factory automation. They have good isolation and good regulation, they droop less under load and they are expensive. The door opener is only used intermittently so you don't need anything this special. eghttps://es.made-in-china.com/co_trugeng/product_DIN-Rail-Door-Bell-Transformer_esghroyyu.htmlOr find a security product supplier.
Saftety Capacitor K rating clarification - Page 1
Forum section: electronics / beginners

author: radlebb
author_rank: Newbie
timestamp: December 10, 2022, 08:26:06 am
content: Hi,I'm a bit confused by the use of K as a capacitance rating on Safety Capacitors. I see lots of people saying that K = uF, though I see other sites saying K is the tolerance, i.e. +/-10%The yellow Dain cap is rated at 0.82K, which would might be 0.82uF with +/-10%. Or does it mean 0.82 x 1000pF, i.e. 820pF or 0.00082uF?I was looking for a replacement so I went with 0.82uF and orderedhttps://www.we-online.com/components/products/datasheet/890324025047CS.pdfThis Wurth cap says it's 824K, which looking at the sheet seems to mean 824,000pF (and in this case the K might not relate to tolerance but means x 1000pF... though it does still say +/-10%)? So that would be 820nF and 0.82uF.So, have I got the right spec replacement here? Or should I have gotten an 820pF?Thanks

author: Kleinstein
author_rank: Super Contributor
timestamp: December 10, 2022, 10:05:22 am
content: The K is to signal the tolerance and not the capacitance.The numbers are usually either µF, pF or a 3 digit code like 123 for 12*10^3 pFSo the 0,82K would be either 0,82 µF or 0,82 pF and 0,82 pF would be way to small to make sense.If in doubt the datasheet will tell - very few series have such a large range that there is any doubt between µF or pF.

author: wasedadoc
author_rank: Super Contributor
timestamp: December 10, 2022, 02:19:13 pm
content: Those are both 820nF.The yellow one is marked as 0.82 (uF). The red one is 82 x 10^4 (pF).

author: TimFox
author_rank: Super Contributor
timestamp: December 10, 2022, 02:59:12 pm
content: Popular tolerance codes for component values:K = 10%J = 5%F = 1%

author: radlebb
author_rank: Newbie
timestamp: December 10, 2022, 09:23:34 pm
content: Thanks all. So in this case since the yellow one is decimal it's likely to be uF and the red one is using the 3 digit convention in pF. Briliant!
Sagging square wave output from non-inverting opamp - Page 1
Forum section: electronics / beginners

author: level6
author_rank: Regular Contributor
timestamp: December 19, 2019, 08:39:42 pm
content: I'm working on a device that generates low frequency triangle and square waves. The final output is amplified by a non-inverting opamp circuit with a gain of about 5. The problem I'm having is the square wave output is not symmetrical, it sags toward zero at both the positive and negative pole. The input into the opamp looks fine, as illustrated by the screen capture from my scope. Yellow is the output, blue the input into the output circuit.What would be causing this and how can I remedy it? BTW the triangle output is fine.Schematic of output circuit attached.

author: David Hess
author_rank: Super Contributor
timestamp: December 19, 2019, 09:02:46 pm
content: The input does not look square to me. The gain multiplies the amplitude but also the slope.

author: level6
author_rank: Regular Contributor
timestamp: December 19, 2019, 09:22:13 pm
content: Quote from: David Hess on December 19, 2019, 09:02:46 pmYou're right. I went back and zoomed in on the input and see that it is just reliably amplifying the input. The input is coming off a voltage divider. That may have something to do with it. More research...

author: StillTrying
author_rank: Super Contributor
timestamp: December 19, 2019, 10:14:07 pm
content: Is the square wave shape good when it's not connected to the 100k, just as a check of the square and scope.Are the +/- supplies to the TL074 good.

author: level6
author_rank: Regular Contributor
timestamp: December 20, 2019, 03:53:51 am
content: Quote from: StillTrying on December 19, 2019, 10:14:07 pmPower supply is fine, it's from my bench supply. I'm going to look into eliminating interaction with other parts and see if that changes thing for the better.

author: Ash
author_rank: Regular Contributor
timestamp: December 20, 2019, 04:02:13 am
content: Does the output jack _really_ short the output to ground when no plug is connected as shown on the schematic? That's probably not a good idea either...Ash.

author: level6
author_rank: Regular Contributor
timestamp: December 20, 2019, 04:38:14 pm
content: Quote from: Ash on December 20, 2019, 04:02:13 amWoops! Thanks for pointing that out. Right now I'm working with a prototype on perfboard and I didn't implement that short. I will certainly change that in the design!

author: Cerebus
author_rank: Super Contributor
timestamp: December 20, 2019, 05:15:54 pm
content: Given the thickness of those traces I suggest that you crank the oscilloscope timebase way up and see what's going on there. I would not be surprised to see that those thick traces are actually oscillation or ringing on the 100mV+ order of amplitude.
sainsmart 7inch TFT LVDS issues - Page 1
Forum section: electronics / beginners

author: steakandcheeseman
author_rank: Newbie
timestamp: December 23, 2014, 09:35:24 am
content: Hey, has anybody else bought those cheapish 7inch 800x480 LCD panels shipped from china ? All the stock images seem to show it at a reasonable image quality, but when I built mine, the image quality was exceptionally low. The colours also morphed when the LVDS cable flexed. Im new to tinkering so I really have no idea as to where to start troubleshooting or what the problem may be.http://imgur.com/a/DB5XX#0

author: rob77
author_rank: Super Contributor
timestamp: December 23, 2014, 11:22:39 am
content: is your flat-flex cable placed precisely and secured tightly in the connector ? on the picture it looks like it's not even perpendicular to the connector.

author: steakandcheeseman
author_rank: Newbie
timestamp: December 23, 2014, 12:00:10 pm
content: I reconnected the flex connector, pushing it as far in as I could, but the image quality is still subpar. Thinking it might be due to an analog input, i plugged it into my Xbox via HDMI. The image quality is still pretty poor. The connector is held tightly and I cant push it in further:http://imgur.com/a/O7bjLI followed this video as the build guide, pulled out the connector tabs, pushed in the flex connector, then pushed in the tabs:

author: steakandcheeseman
author_rank: Newbie
timestamp: December 25, 2014, 01:52:13 pm
content: Has anybody got any other suggestions ?

author: cpt.charlie
author_rank: Contributor
timestamp: December 26, 2014, 12:01:42 am
content: Are you using a proper resolution a refresh frequency for your module? is your board programmed for your tft panel?
Sallen key filter DC biasing problem - Page 1
Forum section: electronics / beginners

author: edgaras006
author_rank: Contributor
timestamp: February 20, 2019, 02:48:14 pm
content: Hello everybody,I designed 8th order low pass filter based on sallen key topology. Tested its transfer function in multi sim and it looked great, but when I assembled it turned out that filter shift DC level of bipolar +-10V signal and halved it. So when I feed in +-10V signal I get -100mv..-10,1V signal. Despite shifted DC level, filter has a correct transfer function, so I am a little lost. What have done wrong?Thanks in advance.

author: Benta
author_rank: Super Contributor
timestamp: February 20, 2019, 05:03:03 pm
content: First, a comment (please take it in a positive sense): that's one of the messiest schematics I've seen for some time.Now for your problem: what does "Input +/-10 V from low impedance source" mean? If the output of your source is AC coupled, you have no DC reference and the circuit will fail. You should never allow external sources to set the DC bias, thismustbe internal to your circuit.

author: edgaras006
author_rank: Contributor
timestamp: February 21, 2019, 08:38:04 am
content: Thanks for the compliment about schematic. It would have been way nicer if I would have not displayed all real components.A source is DC coupled differential amplifier. It seems I have soldered something wrong (possibly shorted something) because another identical PCB works just fine.

author: bson
author_rank: Unknown
timestamp: February 21, 2019, 09:36:14 pm
content: Circuit seems fine, and I have no difficulty understanding the schematic, so fine by me. My #1 guess would be you did something wrong with the supplies, like grounded a -12V supply pin. Second guess would be you accidentally swapped a cap and a resistor.

author: Audioguru
author_rank: Super Contributor
timestamp: February 22, 2019, 03:24:45 am
content: I tidied up part of the schematic:

author: edgaras006
author_rank: Contributor
timestamp: February 24, 2019, 05:38:03 pm
content: It turned out to be damaged opamp. I replaced it and the circuit started up just fine. It looked like as if input transistor gate was damaged by ESD (even if I had ESD wrist strap and was working on ESD mat).Thank you, everybody, for suggestions and advises. Audioguru did a really nice job, thanks.
Salt water chlorinator waveform - Page 1
Forum section: electronics / beginners

author: e100
author_rank: Frequent Contributor
timestamp: April 08, 2012, 09:26:08 am
content: This is the voltage trace that I see from a SCR controlled chlorinator set to about half on.I was expecting the voltage to always return close to zero, but it never drops below about 3v even though the corresponding current trace returns to zero.(different time scale and the 6.4mv line is the real 0v as the scope is out of cal)When switched off the electrodes generate a DC offset of about 1.2v which presumably is the battery effect.So what causes the additional 1.8v offset on top of the base 1.2v during normal operation?A Google search didn't turn up much and I'm not a chemist.
Salvaged 12 volt power supply from 12 volt UPS - Page 1
Forum section: electronics / beginners

author: dclevy1
author_rank: Contributor
timestamp: March 02, 2018, 06:47:57 pm
content: I have a 12 volt UPS power supply that I salvaged from a working UPS unit and I am using it to deliver 12 volts to my various circuits but the problem is I don't know the amperage of the power supply and there is no labels nowhere on it as well as no fuse. So I also looked up a model number on the power supply and I got no result or data sheet. Is there a way I can find or figure out the amperage by looking at the components on the board? Yes I know it's dangerous to use a power supply without a fuse or built-in cut off mechanism I am planning to implement safety measures for this power supply in the near future. If I can use itSent from my iPhone using Tapatalk

author: capt bullshot
author_rank: Super Contributor
timestamp: March 02, 2018, 07:01:06 pm
content: From the size of the components, I'd guess it's a 40W (maybe 60W) supply. For 12V that would be 3A ... 5A. The secondary rectifier diodes look more like 2A than 4A, so to be sure, I wouldn't draw more than 2 ... 3A from this supply. Usually they are overload and short circuit protected by the primary controller IC, so IMO there's no need for additional protection mechanisms. The overload protection may work only for gross overloads, so overloading by 20% or 40% will cook it slowly to death.In general, you can guess the supply's power rating by comparing its transformer and other component sizes to power supplies of known ratings and similar age. Newer ones tend to be smaller at the same rating.

author: danadak
author_rank: Super Contributor
timestamp: March 03, 2018, 09:37:17 pm
content: Another approach, albeit loosely defined, is to run the supply, use a IRhandheld thermometer, record key component temps, then load itto desired load and rerecord heat rise in components. Not by any meansmeant to substitute for design derived limits, but a crude representationof its efficiency and currents.Also any of the semi components marked, look at their datasheets. Ifdatasheet says diode is 5A and you want 50, that's a show stopper, 50Athat is.If you are going to use this in a life support application throw this idea away.Regards, Dana.

author: dclevy1
author_rank: Contributor
timestamp: March 04, 2018, 01:40:19 am
content: Quote from: danadak on March 03, 2018, 09:37:17 pmThank youSent from my iPhone using Tapatalk

author: dclevy1
author_rank: Contributor
timestamp: March 04, 2018, 01:41:26 am
content: Quote from: capt bullshot on March 02, 2018, 07:01:06 pmHmmm appreciate the response. Thank youSent from my iPhone using Tapatalk
Salvaged LCD - Page 1
Forum section: electronics / beginners

author: Crispies
author_rank: Newbie
timestamp: July 30, 2013, 09:11:51 pm
content: I have an lcd board I got from an old broken printer a while ago and I ordered an arduino a few days ago. I thought I might use it with the arduino and try and display some text but i cant find anything on the lcd. I cant figure out the pinout but I could be doing it wrong, on google I found found a post somewhere that said to use 5v, ground then ground the contrast and you could see if it works but I cant figure out which pins are which. Any advice? pics of board with lcdhttp://imgur.com/a/vGgta

author: carbon dude oxide
author_rank: Frequent Contributor
timestamp: July 30, 2013, 09:23:26 pm
content: have you looked under the lcd module for the lcd part number?

author: Crispies
author_rank: Newbie
timestamp: July 30, 2013, 09:28:39 pm
content: Sorry I did but it also couldnt find anything with that 2918ccb is on a sticker on the back of the lcd.

author: Unknown
author_rank: Unknown
timestamp: July 30, 2013, 09:38:45 pm
content: Most likely HD44780 compatible. Based on the PCB, my guess would be (what I call pin 1 is the one on the left in the second picture you provided with the component side down):pin 1: groundpin 2: contrast adjustpin 3: Vccpin 4: Vccpin 5: groundpin 6: RSpin 7: R/Wpin 8: Epin 9-16: D0-D7One of the grounds and one of the Vcc pins will be for the backlight (if available). Putting 5V across them with say a 100 ohm series resistor should make the backlight light up. No guarantees for correct polarity, though. If pin 5 is connected to pin 1 (the ground plane), then I would say my guess for the power pins should be correct. No way to be sure about the data lines (I assumed standard pinout) without trying though. There are plenty of Arduino sketches to drive an HD44780-compatible LCD, but I would suggest to start with a display with a proper datasheet if this is your first time driving an LCD. That removes a bunch of unknowns from the equation. For example, it's possible that this LCD is not even HD44780 compatible.It would be useful to have the board in the printer it was connected to.

author: Crispies
author_rank: Newbie
timestamp: July 30, 2013, 10:04:56 pm
content: Hey thanks man that worked. Its a 20x2 if you were curious. The printer was a big complicated monstrosity so I'm not really sure how it all went together anymore. But when i get my arduino try and figure out the data lines. I wanted to get this one working instead of just buying one since its a nice little board all together with buttons I can just use it in a project.
salvaging components from a clothes dryer. - Page 1
Forum section: electronics / beginners

author: Pirateguy
author_rank: Regular Contributor
timestamp: September 21, 2018, 08:59:18 pm
content: so my clothes dryer broke the locking mechanism of the door but is mechanically and electrically intact.i will be getting a new one and am wondering, besides what must be a fairly beefy motor, what could i salvage from it?also: any safety concerns i need to address?

author: schmitt trigger
author_rank: Super Contributor
timestamp: September 21, 2018, 09:37:42 pm
content: Does the board have an electronic or mechanical controller?If the former, there may be few components, sensors or displays that you could salvage. If the latter, there could be some switches.The power cord. Here in the US, many times they sell you the power cord separately, and because of the heavy wire, it can be expensive.

author: Pirateguy
author_rank: Regular Contributor
timestamp: September 21, 2018, 09:41:08 pm
content: not sure, haven't looked inside yet.the thing has been in use recently so i want to check ifthere are safety issues like with TVs n stuff first.

author: sokoloff
author_rank: Super Contributor
timestamp: September 21, 2018, 10:09:31 pm
content: Electric dryer, once unplugged and cooled, is inert and safe.Gas dryer, once unhooked and gas verified as not leaking, is inert and safe.Might there be a power supply cap that’s charged? Sure. Is it going to bite you? Not hard enough to worry about.

author: Brumby
author_rank: Unknown
timestamp: September 22, 2018, 02:43:16 am
content: If it has an electric heating element - you could use that as a high power resistor. It might not be a convenient shape, though.

author: Rick Law
author_rank: Super Contributor
timestamp: September 23, 2018, 12:24:56 am
content: Quote from: Pirateguy on September 21, 2018, 08:59:18 pmI don't know if your local market is the same as the USA...I know you are talking about dryer, but mywasherexperience my apply. I have replaced a lot of parts on my old washer all from eBay. The timer, the sensors, etc., etc. If you take out the control board you can eBay it. Even the knobs and the leveling screw/legs.

author: ignator
author_rank: Regular Contributor
timestamp: September 23, 2018, 12:30:48 am
content: Fairly minor part to repair and keep using.Unless the motor bearings are failing. But that depends on if the motor is the type that can be taken apart, and repaired.The normal reason to discard is motor burnout, or electronics failure.
Salvaging parts from computer cards - Page 1
Forum section: electronics / beginners

author: Arthur
author_rank: Contributor
timestamp: May 31, 2011, 09:34:24 pm
content: Is it possible?For example, I have a 56k modem with a reed relay, bridge rectifier, speaker, inductor, electrolytic caps and resistors up for grabs if I could get them off the board. But I can't. They are through hole components but of a very fine pitch it seems.I have tried a solder pump and solder wick (the flux impregnated stuff that is hopefully half decent) but it seems that whatever I do, surface tension retains just enough solder to keep the parts stuck tight.I have access to a good quality soldering iron but not a rework station or anything like that. Is there some trick to it, or is it just not possible?I don't have any intended use for these components but then I don't have any use for a 56k modem either, it would only be going in the bin.

author: Mechatrommer
author_rank: Super Contributor
timestamp: May 31, 2011, 09:47:58 pm
content: put alot of solder as one big or long blob on all pin, melt it at once, you can pull the component out. air gun or oven is just easier for this kind of work. practice make perfect. more advance, you can use less solder and slide your iron quickly to melt all at once.

author: tekfan
author_rank: Frequent Contributor
timestamp: May 31, 2011, 10:16:18 pm
content: Use a heat gun. The very one you use to scrape paint off of surfaces.

author: the_raptor
author_rank: Regular Contributor
timestamp: June 01, 2011, 12:49:39 am
content: You either need a heat gun and let gravity do the work, or need to pry the part as you desolder each leg.

author: Zad
author_rank: Super Contributor
timestamp: June 01, 2011, 02:48:17 am
content: It might also be the case that the components have been bonded to the board with a blob of glue. This more usually happens to surface mount devices prior to reflow, but can happen with PTH devices too.

author: Wim_L
author_rank: Regular Contributor
timestamp: June 01, 2011, 06:29:47 pm
content: Another problem may be pins bent to fix the parts into their holes, or even worse, metal shields over the components with barbed spring clips that open and hook into holes in the PCB, and then are soldered. Those are virtually impossible to remove without damage.If it's just through hole, heat guns are perfect. Heat the other side of the board and shake the board until the components drop out. Those heat guns aren't particularly subtle, so you might delaminate the board in the process, and cause all kinds of nasty fumes. Best to do it outside or at least with very good ventilation.

author: sacherjj
author_rank: Frequent Contributor
timestamp: June 01, 2011, 06:50:22 pm
content: I used to use desolder wick to get components that were worth it. For large things that are harder to break, I now love my Atten 858D+ hot air gun. Put a thin screw driver under a relay side and heat as you pry a little. Off in 20 seconds.
Salvaging used electronics. - Page 1
Forum section: electronics / beginners

author: mindentropy
author_rank: Contributor
timestamp: February 23, 2014, 05:04:59 pm
content: Hi,I am interested in salvaging old electronic PCB's like unused set top boxes or DVD players or some old mobile phones. I want to reuse the PCB for other purposes not intended mostly want to flash my code into the microcontrollers or the CPU's. To do this how should I go about flashing assuming the processors are not custom processors or ASIC's but known processors. The JTAG emulators are quite costly for this. Are there any other ways to go about this?

author: PedroDaGr8
author_rank: Super Contributor
timestamp: February 23, 2014, 06:25:44 pm
content: Quote from: mindentropy on February 23, 2014, 05:04:59 pmThis is likely very difficult as best. Quite frankly you are better off just buying your own uC. First off the board is custom for the application. Giving you all sorts of headaches. Second, many will be write protected. Third most boards don't have connectors for writing to the uC. The uC is preprogrammed abd then soldered into place.All of these are very difficult tasks, making this not worth your time.Sent from my EVO using Tapatalk
SAM mcu Low level port driver - Page 1
Forum section: electronics / beginners

author: hsn93
author_rank: Regular Contributor
timestamp: July 09, 2018, 11:45:46 am
content: hello,i didnt know where i should post in Beginners or microcontroller forum..i decided to post here because i feel its simple question:im trying to write low level port driver for SAMD21 series mcu, copying codes from ASF and this what i did:Code:#define LED_0_PIN PIN_PA20#define LED_0_PIN_MASK(1U << (LED_0_PIN & 0x1f))static inline void _gpio_set_OUTPUT(const uint8_t pin){volatile PortGroup *pin_port = (volatile PortGroup *)(&(PORT->Group[pin / 32]));pin_port->DIR.reg = (1U << (pin & 0x1f));pin_port->PINCFG[pin & 0x1F].reg = PORT_PINCFG_DRVSTR;}static inline void gpio_set_pin_level(const uint8_t pin, const bool level){volatile PortGroup *pin_port = (volatile PortGroup *)(&(PORT->Group[pin / 32]));if (level) {pin_port->OUTSET.reg = (1U << (pin & 0x1f));} else {pin_port->OUTCLR.reg = (1U << (pin & 0x1f));}}my question is : am i doing this right way, to set-up pin high and low ?should i call the function like this (without disable cpu irq) ? :Code://cpu_irq_disable();_gpio_set_OUTPUT(LED_0_PIN);gpio_set_pin_level(LED_0_PIN,1);//cpu_irq_enable();

author: ataradov
author_rank: Super Contributor
timestamp: July 09, 2018, 04:52:35 pm
content: It looks ok.There is no need to disable the interrupts unless your application needs it and can't tolerate potential small delay. Keep in mind that if output was not set previously, then it first will be driven to 0 and then set to 1. If you don't want this glitch, then set the output value first and then enable the output.

author: hsn93
author_rank: Regular Contributor
timestamp: July 10, 2018, 07:07:41 am
content: do you mean that by default its "internal pull up" and when i set it up to output .. it will be driven low for short period until i set "OUTSET.reg" ??so it will be like this:---------------------------------------output--------pullup----output 0----------drive 1======1======0==========1===========

author: ataradov
author_rank: Super Contributor
timestamp: July 10, 2018, 07:15:49 am
content: Since pull-up is enabled by setting the output to 1 while pin is configured as an input, you will be fine here.But lets say you had no pull-up or pull-down, just a floating input (or external pull-up), so the output buffer was set to 0. This is not a problem since direction is configured as an input. But then you change it to an output which is high.If you set the high level first, then it still would not matter, since the pin is still an input, so when you switch the direction, it will just cleanly go to "1".On the other hand if you set the direction first, then the output will go to 0 before MCU get to setting the output value high.Same principle applies to PMUX settings. You always want to configure and enable the peripheral before setting the PMUX.
SAM3X8E oscillator problems - Page 1
Forum section: electronics / beginners

author: Aleksander Spyra
author_rank: Newbie
timestamp: November 29, 2020, 07:04:34 pm
content: Hi there!I have recently designed a campervan module. I based it off an Arduino Due, but I had to move to a custom board to utilise all the available pins of the SAM3X8E. I based the design on Due schematics, stripped the mega16u2 and the native USB port and added all the functionality I needed.The assembled board has arrived. I have checked the power supply and programmed a simple blink program using SWD. The upload was succesful, but the LED wasn't blinking.After double checking pin naming etc, the board is still not running the program.As the chip was programmed correctly, I suspect the external 12MHz oscillator. I borrowed an oscilloscope and captured the XIN waveform (identical on both boards).The amplitude is only around 300mV and looks like a sine.Here is the info I collected:My oscillator schematic:https://drive.google.com/file/d/1vwSKC3EPUPUz45JPSo4B4OVt-c6gcqXz/view?usp=sharingDUE oscillator schematic:https://www.arduino.cc/en/uploads/Main/arduino-Due-schematic.pdfDatasheet of the oscillator I used:https://datasheet.lcsc.com/szlcsc/Yangxing-Tech-X322512MSB4SI_C9002.pdfMy top layer:- here I made an error, the ground fill shouldn't connect to the crystalMy bottom layer:SAM3X8E datasheet (page 1397):https://ww1.microchip.com/downloads/en/DeviceDoc/Atmel-11057-32-bit-Cortex-M3-Microcontroller-SAM3X-SAM3A_Datasheet.pdfI have tried desoldering the load capacitors (I calculated 33pF instead on Due's 22pF), the waveform didn't change. I also tried to change the VDDPLL ferrite bead to one desolder from a faulty Due board. I've also swapped the crystal to the one from Due.I cannot find my error. Maybe you can see whats wrong?

author: ataradov
author_rank: Super Contributor
timestamp: November 29, 2020, 07:41:41 pm
content: This is a correct behaviour for the crystal oscillator. Perfect, actually.Look for some other reason, but enough of your code runs to configure and enable the oscillator, which is good. Now debug the rest.

author: Aleksander Spyra
author_rank: Newbie
timestamp: November 29, 2020, 08:13:53 pm
content: Good to know! I wanted to check with a Due board, but the one I have is fried and I'm waiting for another to arrive.I wonder if the lack of USB circuitry can bother the Arduino startup code, as there really isn't much that can go wrong with a blink sketch. Or maybe the way I program it (PlatformIO + STLink) may be problematic... When the new Due arrives, I'll be able to try programming it the same way - this way I will be 100% sure it is not a hardware problem.Thanks!

author: ataradov
author_rank: Super Contributor
timestamp: November 29, 2020, 08:29:35 pm
content: I have no idea about Arduino and its dependencies.But if the oscillator runs at all, your programming method is probably fine.