hybridfree/eevblog-posts huggingface dataset:
PSX Station controller to PC adapter - Page 1
Forum section: electronics / projects

author: Jaunedeau
author_rank: Regular Contributor
timestamp: December 31, 2024, 01:53:07 pm
content: Just to have fun and learn things, I' trying to add PSX controller support to an opensource game controller firmware (gp2040-ce).I usethis documentationfor the PSX protocol.Thing seem relatively accurate, but I get really strange levels. On the controller answer here (in dark blue, cursors show the 0V and 3,3V of the data line), you see the levels :- change on clock rise (clock is cyan)- is very low for "1" after a "0" has been sen and slowly rises.Decoding sometimes work on the oscilloscope because I can choose the levels, but fail on the rp2040.I've tried :- checking every connection for bad breadboard connection, bad solder and shortcut : everything seems fine.- slowing down the speed (trace is at half the nominal speed)- activating or disabling pull up and pull down on the GPIO- powering the controller with 5V instead of 3V3 (this is third party controller, but original one have been tested in 3-5V range and works fine)Any idea what could be going wrong ? (I no lnoger have a playstation to test the controller, maybe it just doesn't work, but the problem could be on my side also)

author: Jaunedeau
author_rank: Regular Contributor
timestamp: January 01, 2025, 12:16:27 am
content: Part of the answer was that the pullups on the rp2040 are very weak (I measured them around 90kr). Using an external potentiometer, it seems 6.8kr is a way better value.Also the value needs to be sampled not in the middle of the cycle, but a bit after the clocks goes up (for 250kHz, I let 2us of clock down, rise clock, wait 1us, sample the value, then wait another value)This still does not work thought, but I guess the problem is now how I interface with the firmware I use, not reading the value. Ill have to make test tomorrow.
Psychotic Oscilloscope Idea: Tube to Transistor - Page 1
Forum section: electronics / projects

author: PhynixViking
author_rank: Regular Contributor
timestamp: December 17, 2012, 12:45:44 am
content: Ok, yea as the title says I have a crazy idea... how hard to you think it would be to COMPLETELY convert a old 1960's 2CH oscilloscope to be completely transistor based? (except for the CRT of course)Why would I? Well its kinda a nice oscilloscope but I'm afraid the tubes are going to burn out any day. I believe they are mostly the original tubes most of them the ink is long-gone worn off... as well as it might be a fun project to help me learn more about tubes and transistors.Is there some place that has a "tube to transistor conversion schematic" or something?

author: c4757p
author_rank: Super Contributor
timestamp: December 17, 2012, 03:00:58 am
content: The transistor type that is closest to the vacuum triode is the N-channel JFET. By the time you locate and purchase a set of JFETs with the voltage and power ratings of triodes you might as well have replaced either the tubes or the entire scope. Good luck if they have anything involving more electrodes than a triode and they're doing something unconventional with it. And fitting in anything but a JFET into that circuit is tantamount to designing your own oscilloscope from the ground up. Note that even if you did put in JFETs and by magical coincidence they were similar enough to work, you'd still have to rebias the whole circuit.Interestingly, there were at one time solid-state tube replacements that were JFETs with some circuitry to compensate for differences in characteristics. Most of them only worked properly in specific circuits.

author: MartinX
author_rank: Regular Contributor
timestamp: December 17, 2012, 06:34:04 pm
content: I have also had this idea and then rejected it, it will take forever to figure out how each tube is used and then build a transistor equivalent that fits. I thought it was a better idea to replace an entire function block in the scope, like the vertical amplifier with a modern circuit having the same function, in the end I found a more modern scope that I could afford, so I still have the old scope in its original condition and now I am glad I didn't destroy it.

author: SeanB
author_rank: Super Contributor
timestamp: December 17, 2012, 06:36:34 pm
content: Most scope tubes are pretty common types, and are available as either NOS or current production from Soviet era factories. For the few that are made of unobtanium there are modifications to use more modern components in their place.
PT100 Differential Amplifier - Page 1
Forum section: electronics / projects

author: rudika79
author_rank: Regular Contributor
timestamp: October 17, 2014, 01:25:05 pm
content: Hi,I have problem with differential amplifier which not working how should be. The circuit is not designed by me and I can speak with design engineer in this moment. The problem is the output (UT+ and UT-) I measuring all the time same voltage. Not changing when is changing resistance on PT100 probe. When I measure input voltage on AJ4 connector then I can measure changes on PT100 probe. In this moment, I use 138.51ohm for 100°C and 175.86ohm for 200°C resistor to emulate PT100 probe. I checked PCB for obvious fault like short, component not soldered properly, component on right place, power supply voltages and noise.Here is what can I measure on circuit.when I am using 138.51ohm for 100°CBetween AJ4 connector pin 2 and 3 : 0.238VBetween UT+ and UT- output measured : 2.321V (should be around 1.95V)when I am using 175.86ohm for 200°CBetween AJ4 connector pin 2 and 3: 0.308Between UT+ and UT- output measured : 2.321V (should be around 2.45V)Vcom is 2.5VI'm just start to running out of idea what is problem whit circuit.I just need idea what could be wrong whit this circuit. And I will be need to repair it....Thank you,Rudolf

author: awallin
author_rank: Frequent Contributor
timestamp: October 17, 2014, 05:03:58 pm
content: Quote from: rudika79 on October 17, 2014, 01:25:05 pmlooks like the ADA4932 is configured for a gain of 10, so you might see "clipping" because your input voltage is too high (or your gain is too high).Try reducing the gain by lowering R99 and R102 by 2x or 5x and see what happens.If you want to optimally fill the dynamic range of an ADC you should be comparing the PT100 resistance to some reference resistor that corresponds to the middle of your desired measurement range.ADA4932 with a bandwidth of ~500MHz seems way overkill for a PT100 measurement. Why not use a low bandwidth DC-accurate instrumentation amplifier (AD8221 ?) or zero-drift op-amp?

author: MK
author_rank: Regular Contributor
timestamp: October 18, 2014, 07:38:19 am
content: you have about a 150-160 mV voltage across the resistor that you are amplifying by the ad4932, so a max gain of 25 will clip at temps above 200 C or so, is the AD4932 specified for rail to rail input, as yours is sitting up at 5 V? You need a differential cicuit so that you see just the change in resistance, just blindly using a differentail amp is not the answer.

author: rudika79
author_rank: Regular Contributor
timestamp: October 20, 2014, 07:58:08 am
content: Thank you for your replay MK and awallin! I found the problem. The gain was to high.... I reduced a gain and start to get output changes...Thank you,Rudolf
PT100 Temperature Sensor - What are best practices for grounding/shielding? - Page 1
Forum section: electronics / projects

author: edpalmer42
author_rank: Super Contributor
timestamp: December 06, 2020, 09:51:15 pm
content: What are the best practices for shielding PT100 sensors? Do they need it or is it optional?I have a Fluke/Philips PM2534 DMM. It can measure temperature via a PT100 probe. I bought this sensorhttps://www.ebay.com/itm/223475090836to make a probe and it works fine. My boiling water test was about 1C off after adjusting for air pressure and my ice/water temperature was about -0.1C. Both are quite acceptable to me.I ran into a puzzle when I went to attach the DIN plug that plugs into the meter. The metal tip of the sensor is attached to the braid in the cable. Although the manufacturer attached banana plugs to the four leads for the sensor, nothing was done for the braid. When I looked at the meter to see how it handled this question, the shield on the DIN socket isn't connected to anything.Should the sensor braid and therefore the tip, be grounded? Normally, you shouldn't be measuring temperature on live equipment, but sometimes you have to. The idea of poking a grounded metal object into live equipment doesn't appeal to me.What if I used a safety-rated capacitor to provide an AC ground for the shield? Still not ideal, but at least I wouldn't be grounding out the mains or DC voltages.Any thoughts?
PT1000 over distance, possible safety features - Page 1
Forum section: electronics / projects

author: Radiosonde
author_rank: Contributor
timestamp: June 21, 2019, 04:08:49 pm
content: HelloFor my home weather station I plan to utilise PT1000 RTDs , I would design a PCB with a SMD RTD on it which can slide in a already existing Thies sensor radiation shield, it would be connected via 4 wires over 20m of shielded cable.For readout I plan to use an MAX31865, the datasheet insists in a 10nF capacitor mounted between the two sensing lines.Should I place this capacitor on the PCB or on the readout board?Are there any other suggestions regarding to necessary components directly at the RTD or can I leave it just like that?Regards

author: Siwastaja
author_rank: Super Contributor
timestamp: June 21, 2019, 04:11:17 pm
content: Next to the MAX31865, so it filters differential noise coupling to the wires, and also provides ESD protection.
PT2262 RF ENCODER - Page 1
Forum section: electronics / projects

author: stern0m1
author_rank: Contributor
timestamp: February 13, 2020, 09:24:24 pm
content: Is there something similar to the PT2262 Encoder that the address bits are randomly set by the manufacturer of the chip? Requiring no programminghttp://www.princeton.com.tw/Portals/0/Product/PT2262_5.pdfThanks!

author: floobydust
author_rank: Super Contributor
timestamp: February 13, 2020, 10:55:47 pm
content: One alternative isPT2272or Holtek HT12E or EV1527 (learning code) orHoltek HT6P20.Most of the new tech IC's are code-learning. That PT2262 IC is low security because it uses fixed code and vulnerable to copycat attacks.Linxsells the complete remotes, receivers, IC's too from Digikey.

author: stern0m1
author_rank: Contributor
timestamp: February 13, 2020, 11:37:47 pm
content: Thank you for the information.All of these require, in one shape or another setting the "address". No one makes an encoder with an option for the "address" to be just randomly set by the ic manufacturer?

author: floobydust
author_rank: Super Contributor
timestamp: February 14, 2020, 01:05:02 am
content: EV1527has a factory 20-bit address (1,048,576) pre-programmed I think. It's just a button press on the receiver to learn and accept this. This IC part is in many eBay little remote boards.

author: stern0m1
author_rank: Contributor
timestamp: February 14, 2020, 09:56:48 am
content: Which chip is used to decode ev1527?Thanks

author: ebclr
author_rank: Super Contributor
timestamp: February 14, 2020, 06:51:56 pm
content: http://www.sc-tech.cn/en/2272en.htm

author: stern0m1
author_rank: Contributor
timestamp: February 14, 2020, 10:07:48 pm
content: How do you set it to" learn" the preprogrammed address in the 1527?The datasheets are not really clear.Thanks
PTC identification - Page 1
Forum section: electronics / projects

author: bdunham7
author_rank: Super Contributor
timestamp: December 27, 2024, 06:16:55 pm
content: Can anyone identify the manufacturer and part number of this PTC thermistor? It is commonly found in compact Fluke meters of various types. I only find Chinese listings on sites like Taobao.

author: thm_w
author_rank: Super Contributor
timestamp: December 27, 2024, 09:37:02 pm
content: https://www.mantech.co.za/datasheets/products/MZ11-AMPRON.pdf1100 ohm PTCNot sure if its a custom part, as other threads say ~1000V rated and these are only 550V. Can compare the size.There is one 1kv rated part on digikey: YS4020

author: bdunham7
author_rank: Super Contributor
timestamp: December 28, 2024, 01:29:09 am
content: The 1.1K 550V "working voltage" PTC would be p/n MZ11-07M112M550 but that doesn't quite match up to what is in the meter. I measured the two PTCs cold at 1111 and 1171 ohms, dimensions 7.4D and 4.9T. So it is thinner, to start. I thought the "R" might indicate the 140C switch temperature, but my thermal camera indicates 100C or so. Perhaps there's a big difference between internal and external but I doubt it. The only picture of it that turns up on the web is Russian site that may not even have the correct photo.Another thing that turns up for that p/n is the Intertek certification for the UNI-T UT181A where it lists the safety components. It indicates that the part is rated for 550V "working" and 1000V "withstand". The UT181A appears to use 4 of these and is rated CAT III/1000V. This seems to be pretty marginal for a Fluke design, so I'm guessing it is a custom part. I'd like to get my hands on some, but aside from junk meters that looks difficult.Quote from: thm_w on December 27, 2024, 09:37:02 pmYes, that's the one I like to see in a DMM.

author: bdunham7
author_rank: Super Contributor
timestamp: December 28, 2024, 03:23:39 pm
content: Quote from: thm_w on December 27, 2024, 09:37:02 pmWhere can I find these other threads?

author: thm_w
author_rank: Super Contributor
timestamp: December 30, 2024, 10:10:38 pm
content: Quote from: bdunham7 on December 28, 2024, 01:29:09 amThe R should be the switch temperature yeah, so not sure why that doesn't line up with the datasheet.You could also try externally heating with a heat gun.The 1kv was from comment here:http://mrmodemhead.com/blog/fluke-87-fusible-resistor/"RT1 is a 1K-ohm @25C PTC (positive temperature coefficient) thermistor rated 1000V, 40% tolerance".https://www.eevblog.com/forum/testgear/fluke-8060a-accidentally-killed-resistance-function-need-help/But looks like that a different older part, not this round PTC.
PTC resettable fuse size required for protecting a Gopro? - Page 1
Forum section: electronics / projects

author: andrewbostaph
author_rank: Newbie
timestamp: August 04, 2018, 05:24:21 am
content: Hi everyoneI have a pcb project and would also like to charge a Gopro Hero 4 Black through the charging cable from a 5V/10A power supply. It is known (though an accurate current data logger) for my camera to draw more than 2A at times (from another 2A supply) causing the gopro to get very hot and freeze up. I wanted to add a resettable fuse to stop it from getting hot. Dont care if the resettable fuse switches on and off here and there but just some protection from the 10A burning out the gopro. The project requires me to use this power supply only (Damn...) I was looking at a belfuse 1.1A continuous 2.2A trip. Anyone have any suggestion on what would be more suitable?-Andrew
PTC Spa Heater Element - Page 1
Forum section: electronics / projects

author: Fresser
author_rank: Unknown
timestamp: July 11, 2018, 08:51:53 pm
content: I have a Lay-Z-Spa inflatable spa that I am reprogramming to add/change some functionality, but I am having trouble understanding how to control the built in PTC heating element, I have reverse engineered the power relay circuit for the heater, the heater has 4 wires, two wires labeled A and two labeled B, I tried to measure across the 4 wires, between A wires I get 1K5 ohms and between B wires I get 520 ohms, all other combinations i get above 500K ohms. The resistance i measure does not make sense to me since it should be a 2000W heater, so i was expecting a much lower resistance.Does anybody have some ideas for what I am missing here, I have attached a pic of the heater and the simple reverse engineered diagram.Thanks.

author: xani
author_rank: Frequent Contributor
timestamp: July 11, 2018, 11:54:33 pm
content: Put in in freezer for some time and measure again
PTC Thermistor Based Discharge Load - Page 1
Forum section: electronics / projects

author: yshrestha
author_rank: Newbie
timestamp: April 11, 2018, 08:18:34 pm
content: Hello,I am trying to make a circuit that slowly discharges a multi-cell lithium battery to storage voltage. I want to support 2s to 6s batteries so we are talking about voltages ranging anywhere from 7.6v to 25.2v. I am shooting for 500mw of power dissipation so I can achieve my form factor requirements for the PCB (11mm x 15mm). Ideally, the same circuit can discharge any cell voltage with relatively constant power based on ambient conditions (more power dissipation in colder ambient temps, lower in warmer ambient temps) and feature overcurrent and overtemperature protection. So far I have tried/considered:- PTC Thermistor load. This will essentially run the PTC perpetually in its "tripped" state. I have an NTC thermistor in series to handle the inrush current until the PTC heats up and protects the circuit. This best captures what I want. However, I contacted a support engineer and they say the use case is not specified and could negatively impact the life of the device.https://www.murata.com/en-us/products/thermistor/ptc/prg.I have bench tested this and found it to work great and checks off all of my requirements but I am wary of using a resettable fuse as a power resistor essentially.- BJT with an NTC thermistor switching a resistive load on or off. I would preferentially avoid this due to extra components necessary.- I would like to stay away from MCU controlled constant heaters for simplicity sake.- I want to stay away from DC to DC converters if possible.I have attached my proposed schematic. Any help will be appreciated.

author: MosherIV
author_rank: Super Contributor
timestamp: April 11, 2018, 09:11:45 pm
content: HiThe classic way to discharge batteries is with an 'electronic load'See thishttp://www.ko4bb.com/Test_Equipment/DynamicLoad/You are wanting a cut off at a particular battery voltage. You can do this by adding another opamp which compares the battery voltage against a Vref. Use the output of the opamp to either turn off the power transistor or pull the set point voltage to 0V
Pull-up or direct connect? - Page 1
Forum section: electronics / projects

author: Gizmo
author_rank: Regular Contributor
timestamp: October 25, 2014, 08:19:22 am
content: I've got a chip and I want to just connect logic high to a pin, is there any issue with just connecting directly to Vcc, or is a current limiting resistor a good idea?In this particular case I have some 245 bus transceivers and I'm setting the direction of each permanently by either connecting DIR to GND or Vcc. This all works fine, but I was wondering if this will increase current draw or potentially damage the IC by not having a resistor in-line?Thanks!

author: con-f-use
author_rank: Unknown
timestamp: October 25, 2014, 08:48:36 am
content: The datasheet should tell you the input impedance and maximal current rating of the input pins. Based on that you can calculate whether you need an input resistor. Also ESD is somethimes a consideration if the pins are exposed and someone might touch them.

author: TonyStewart
author_rank: Contributor
timestamp: October 25, 2014, 08:53:56 am
content: Test Engineers frown ondirect connectsto Gnd or Vcc because they lose the ability to test if that input is faulty which may be an indication other parts in use on that chip are almost faulty. So a single pullup for all unused inputs or connected to an unused output, which can be be back-driven by ATE.As I recall it was only TTL that demanded a shared pullup resistor for current limiting on overvoltage on the supply to the input.

author: Gizmo
author_rank: Regular Contributor
timestamp: October 25, 2014, 09:02:59 am
content: Hmm, I've had a look at thedatasheetbut don't really know what I'm looking for. Would it be "Control inputs" listed as 1uA max? In which case that's all good.I'm less bothered about testing as I know it's all setup correct and it's a dead simple board (only 7 IC's, most of which 245's). I'm more interested in unnecessary current draw as this is battery powered.

author: Tandy
author_rank: Frequent Contributor
timestamp: October 25, 2014, 12:04:17 pm
content: Using a resistor or directly connecting will not make any difference to the current used. Holding an input high or low essentially uses no current, a pull-up or pull-down resistor only consumes current while they are being overridden to change state.

author: Gizmo
author_rank: Regular Contributor
timestamp: October 26, 2014, 06:25:55 pm
content: Excellent, thank you for the response!

author: dannyf
author_rank: Super Contributor
timestamp: October 26, 2014, 11:13:45 pm
content: QuoteNo need to have serial resistors if you think the mcu will never encounter unexpected conditions.
Pulse current generator design - Page 1
Forum section: electronics / projects

author: anton_vmnnk
author_rank: Newbie
timestamp: February 17, 2023, 12:13:36 am
content: Hello everyoneI'm trying to build such a device:Input: a constant DC voltage source of 50V 3A.Output: a 1 ohm resistor is connected as a load.The generator must produce rectangular current pulses passing through the resistor. These pulses should have the following parameters:1. Amplitude: 30A2. Frequency: 25kHz3. Duty cycle: 15%Power calculations seem to show that such a device should exist:Input power: 50V*3A = 150WOutput peak power: (30A)^2 * 1 Ohm = 900WAverage output power: (30A)^2 * 1 ohm * 0.15 = 135 WattsThat is, the output power is less than the input, which inspires hope.Naturally, I would like to get the simplest possible device from cheap components. Probably it is possible to do this using FPGAs or fast controllers and fast mosfets, but I would like the simplest possible implementation.If anyone has any ideas, please share. I am interested in the architecture of the generator. I can calculate myself the specific nominal values of the parts and so on.If some input data is missing, I will add it without any problems.

author: Marco
author_rank: Super Contributor
timestamp: February 17, 2023, 12:17:00 am
content: If the 1 Ohm is dependable, the simplest solution is a switching power supply to get 30V and then just feed that to the resistor with PWM. No need to have a current source for a resistor.If it's not dependably 1 Ohm, then the margins are too little regardless.
Pulse extender - ish - Page 1
Forum section: electronics / projects

author: tim_d
author_rank: Newbie
timestamp: November 10, 2013, 11:32:12 pm
content: Hi all,I'm looking for a form of pulse extender, but not exactly what a monostable 555 provides. Basically, I'm looking at an audio signal, and want a trigger when the signal peaks outside an envelope, and hold the signal high for a period after the signal finishes exceeding this envelope. My current plan is to use a pair of comparators to detect the audio signal crossing the positive and negative ends of the envelope. Each of these will be generating a series of short pulses - I'd like to feed each into some form of extender functional block to hold high for the duration of the timeout after the last falling edge it saw, and then drop low again. These two will then feed an and gate and that signal is the output. The timeout would ideally be provided by a (presumably dual) potentiometer.Any advice on where to go with this? Even the name of the functional block I'm actually looking for would be helpful. I should note that I've picked up electronics by doing, so I've got enormous gaps in my knowledge, 555s being one of them!Thanks.Tim
Pulse Generator - Page 1
Forum section: electronics / projects

author: guscrown
author_rank: Regular Contributor
timestamp: July 22, 2020, 08:26:19 pm
content: Alright, I haven't done something like this since college, and I kind'a have the idea of what I need to do, but I can't seem to figure out.I'm trying to generate a pulse from an input signal. The signal is normally high, and will go low to activate a device. The generated pulse should be HIGH for as long as the input signal is low, and after the input signal goes back to high, the pulse will remain ON for X seconds.I started refreshing my memory about monostable multivibrators so I fired up Proteus to try and simulate something but it's just not working like the datasheet says it works, and I don't know if this is a simulator problem, or a circuit problem. Doesn't matter what values I set for R and C, the output pulse is always the length of the time constant.

author: OM222O
author_rank: Frequent Contributor
timestamp: July 22, 2020, 08:34:18 pm
content: you first need an edge detector to find the rising edge and send a very quick pulse to reset a monostable timer. Can be easily done via a 556 timer (2 555 timers in 1 package).Then you can OR the inverse of the signal with the output of the timer (timer should be active low as well).

author: guscrown
author_rank: Regular Contributor
timestamp: July 22, 2020, 09:12:36 pm
content: Thanks for the advice. I re-did the circuit, not using the 556 you suggested, but I arrived at something that appears to work as I intend.

author: OM222O
author_rank: Frequent Contributor
timestamp: July 22, 2020, 09:41:54 pm
content: You can filter out the small "glitch" in the transition period using a very small value RC filter too.

author: guscrown
author_rank: Regular Contributor
timestamp: July 22, 2020, 09:54:47 pm
content: Thanks for the help.Now I just need to figure out if Proteus' model for the 74HC123 is broken, and hence I can't really change the pulse width. The circuit looks correct, at least according to the datasheet, and other examples I've seen online.

author: eblc1388
author_rank: Frequent Contributor
timestamp: July 23, 2020, 01:28:38 am
content: Another way to achieve your goal, using CD40106B hex inverter. Change value of R1 for the length of "x seconds" after feed signal goes high.
Pulse Multiplier helpppp - Page 1
Forum section: electronics / projects

author: dorimon100
author_rank: Newbie
timestamp: January 15, 2023, 07:00:03 am
content: Hi guys , im making a carrier board and one of the things required from me is to create some sort of a sync circuit , when one component sends a sync pulse and the circuit sends this pulse to 3 different components. now i bet there is some sort of ic that can do that but i cant seem to find one..could you advice please?thanks.

author: coromonadalix
author_rank: Super Contributor
timestamp: January 16, 2023, 05:50:45 pm
content: what are the pulse specsyou dont give much to work on

author: Marco
author_rank: Super Contributor
timestamp: January 16, 2023, 06:40:12 pm
content: Clock driver or buffer or fanout buffer.

author: ejeffrey
author_rank: Super Contributor
timestamp: January 16, 2023, 10:05:22 pm
content: Depends on the speed and jitter needs, as well as the voltage and load you need to driveFor ordinary applications a CMOS hex inverter / buffer such as 74HC04/34 will work just fine. Tie all the inputs together and wire the outputs however you need them. If you need to drive a low impedance like a 50 ohm load you can parallel multiple outputs.At the other end of the spectrum are dedicated differential ECL clock buffers that will provide extremely low jitter.Once you have the specs it's pretty easy to narrow it down.

author: dorimon100
author_rank: Newbie
timestamp: January 17, 2023, 07:10:28 am
content: thank you!
Pulse polarity confusion - Page 1
Forum section: electronics / projects

author: @rt
author_rank: Super Contributor
timestamp: December 12, 2016, 02:25:52 pm
content: Hi GuysThis is to do with my core logic project which was a smashing success tonight by the wayexcept one thing is confusing me.I have a pulse that is supposed to be shifted out of the last core of a shift register, and it is. I can see it on my scope as a negative going pulse.The thing is, the pulse is induced by the switching of the core, and exits through an independent winding.I want a positive going pulse, so I figure I should simply swap the wires of the winding, but then I see the same negative going pulse on my scope!How can that be?The pulse was supposed to be sensed by a 2N3904, and then off to a microcontroller, which was working nicely, but needs a positive going pulse.Cheers, Brek.
Pulse Rate Measurement System - Page 1
Forum section: electronics / projects

author: jagjeet k
author_rank: Newbie
timestamp: November 03, 2014, 09:46:56 am
content: I had a project kit for the above project and it used a pulse rate sensor that was clipped to the ear lobe for sensing. I think the sensor had some IR reflection type sensor, its damaged now. I want to try making a sensor myself, but dont have much idea about this, can anyone help me with some start off information.http://www.ingenstech.com/projects/pulse-rate-measurement-system/

author: Richard Crowley
author_rank: Super Contributor
timestamp: November 03, 2014, 10:11:47 am
content: There appears to be a popular sensor that is used by the RaspberryPi crowd, and avaiable on Ebay for ~$5For example:eBay auction: #http://www.ebay.com/itm/Heart-Rate-Sensor-Pulse-Sensor-for-Arduino-Mega-Raspberry-new-/251617042377?pt=LH_DefaultDomain_0&hash=item3a958b5fc9

author: jagjeet k
author_rank: Newbie
timestamp: November 03, 2014, 11:46:03 am
content: Thanks Richard, the listing was removed, but I got the idea.
Pulse skipping on Vneg of TPS65130 - Page 1
Forum section: electronics / projects

author: thmjpr
author_rank: Regular Contributor
timestamp: January 18, 2020, 10:32:54 pm
content: TPS65130Split-Rail Converter with Dual, Positive and Negative Outputs (300mA typ)Datasheet:http://www.ti.com/lit/ds/symlink/tps65130.pdf5V in and getting +/- 8V out.Positive supply is working fine, 1.3MHz constant, with minimal ripple:Negative supply is stuck in pulse skipping mode producing a ton of ripple:The device has power save mode, enabled by pulling PSN (power save negative) or PSP to Vin. Disabled with Gnd.Soldering:- PSN and PSP pin continuity checked to Gnd, looks ok under microscope as well.- I only had the one chip (new from LCSC), so will update when I receive and test another chip. Going to try a TPS65131 as well (higher current version).Inductor:- 4.7uH recommended, 10uH is being used. Tried a 4.7uH and skipping was still present.Load:- No load or 20mA load didn't change anything.Anything I might have missed?Some other discussions:https://www.eevblog.com/forum/projects/tps65131-split-rail-power-board/https://e2e.ti.com/support/power-management/f/196/t/717199?TPS65131-negative-output-voltage-abnormal

author: SiliconWizard
author_rank: Super Contributor
timestamp: January 19, 2020, 01:08:39 am
content: Sorry if I've missed it, but I didn't see any capacitor at +Vo and -Vo.That's probably going to be a problem.

author: thmjpr
author_rank: Regular Contributor
timestamp: January 19, 2020, 03:35:48 am
content: Quote from: SiliconWizard on January 19, 2020, 01:08:39 amMy fault, its in another area of the circuit. 47uF on each +Vo and -Vo to Gnd. 25V 47uF X5R.Recommended value is 22uF.Making it larger might help but I suspect it will still skip.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 19, 2020, 06:06:32 am
content: Are you sure it's not compensated incorrectly?Pulse skipping is, well, skipping pulses, but that's a burst waveform. Some controllers still do that, but I don't know if that's typical for this one.Tim

author: thmjpr
author_rank: Regular Contributor
timestamp: January 20, 2020, 07:43:58 am
content: Quote from: T3sl4co1l on January 19, 2020, 06:06:32 amYou are right the terminology is confusing, its more of burst/sleep mode. TI seems to like to call it that:QuoteI've tried with Cn, compensation cap removed, no major difference seen there.With Cf-, feedforward capacitor removed, duty cycle of the pulses increases to ~%50, ripple reduces significantly, and power consumption goes up a bit. So thats on the right path. But removing it is too risky.Note here about >33uF not recommended, but I'm getting same issue with lower values:https://e2e.ti.com/support/power-management/f/196/t/799796Also there, at a point below ~80mA on the Vneg, discontinuous conduction occurs.When testing today I found dropping Vin from 5V to ~4.2V would kick it out of power-save mode and into normal PWM. It would also get into some wild states above 5.3V. Might need to play with that a bit more..
pulse transformer vs digital gate drive for H-bridge? - Page 1
Forum section: electronics / projects

author: SuperJeep
author_rank: Contributor
timestamp: November 26, 2013, 04:01:14 pm
content: Hi,All the application notes I have read on this topic seem to suggest these digital gate drive solutions (ADUM3223 for example)are an amazing substitute for a traditional pulse transformer-not to mention how much more simplifiedthe control logic is.My question is: Does anyone have any reasons or thoughts as to why these should not be used as a replacementto a pulse transformer driving Full H-bridge(regards to isolation/safety)? The type of inverter in the application im consideringis a bipolar square wave generator with <500V high side and approx 1.5A max output.Thank you for any thoughts/opinions on the matter!

author: penfold
author_rank: Frequent Contributor
timestamp: November 26, 2013, 08:20:18 pm
content: The only real point I can think of is part availability. You can pretty much guarantee that 10 years down the line mankind will still have the capability to manufacture a pulse transformer, whether it be in house or externally as a custom part, but its often difficult to tell how long an IC will continue to be produced and how the prices will change in the long term.Further to that, a pulse transformer is easy to manufacture with very high voltage withstand but is also quite predictable under faults. If a crack forms in an IC coupler then there's potential for some unexpected breakdown in isolation, if by some bizarre coincidence all the insulation disappeared from the wire of a transformer then there is still a physical separation between the windings,

author: SuperJeep
author_rank: Contributor
timestamp: November 28, 2013, 04:06:52 pm
content: Thank you for the feedback. I appreciate it. I have decided to move forward with this digital isolator because I have an isolated supply available for the output. Its functionality is somewhat like an integrated pulse transformer only the digital control only requires a single pwm input source (and a second one to complement it in a full bridge design). I just needed to scope out some opinions on the matter because it's always good to see things from a different perspective. Thanks again guys!
Pulse/strobe timeout circuit for a thermal printer? - Page 1
Forum section: electronics / projects

author: Artlav
author_rank: Frequent Contributor
timestamp: December 04, 2014, 03:55:38 pm
content: I have a thermal printer module that i want to connect to a microcontroller.The module have an active-low "burn" input, which heats up the printing elements.This input must not be active for more than several milliseconds, or else the module would burn up itself.Now, i don't trust my ability to never ever make an error in software that would result in this line getting stuck low for long or permanently, so i wanted to add a hardware safeguard.The circuit should immediately give out high when input is low, and low when the input is high (i.e. the pulse can be terminated before the time out).If the input stay high for more than a given time, it should revert the output back to high (safety timeout).If the input were to be left floating, the output should stay high (fail-safe).Here is what i came up with.The resistor dividers are set up in such a way as to always keep the non-inverting input above the inverting one, with a delay capacitor on the former to slow it down. The time it takes to charge the capacitor is our valid pulse window.Questions are:-Is that a good solution? That is, would it work as described?-How is this problem solved normally, i.e. in cash registers? That is, can it be made simpler?

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: December 04, 2014, 07:27:47 pm
content: Too much stuff. Why not code in a watchdog/regular timer interrupt that sets the port every x milliseconds?

author: Artlav
author_rank: Frequent Contributor
timestamp: December 04, 2014, 07:52:16 pm
content: Quote from: Alex Eisenhut on December 04, 2014, 07:27:47 pmWhat if i code it wrong, or something would get broken before the code gets to it, or interrupts would get disabled and forgotten to be reenabled?Pooff!Out goes the magic smoke.

author: Artlav
author_rank: Frequent Contributor
timestamp: December 05, 2014, 09:12:13 pm
content: In case anyone googles that up, i built it and it worked perfectly.Unfortunately the printer still went up in smoke, but it was due to me screwing up it's pinout, not due to any fault in the protection circuit.Fortunately, i only connected one half of the power supply pins, so the other half remained intact, and i was able to get it running (at half the speed, just in case).

author: amyk
author_rank: Super Contributor
timestamp: December 05, 2014, 10:04:09 pm
content: All you basically need is a high-pass filter. How about a cap with a pullup resistor and Schmitt trigger inverter on the other side?
Punched laminate transformers - Page 1
Forum section: electronics / projects

author: excitedbox
author_rank: Regular Contributor
timestamp: December 27, 2019, 03:02:11 am
content: I was just looking at transformers and thinking, why are they made out of flat laminates that are punched out instead of strips of steel that are stacked and bent?It would be the same as wound coil transformers but with the cost benefit of stacking laminations. Is it more expensive to bend cut strips or is there an electrical reason for it? Isn´t it better to have flat wide eddy currents instead of having "thick" eddy currents in the stamped laminate?

author: viperidae
author_rank: Frequent Contributor
timestamp: December 27, 2019, 05:57:54 am
content: It's one less step I guess. Stamping if stamping. You can either stamp E and I shapes and stack them up, or stamp I shapes, then bend them, then stack them.The bending method would also require different length pieces and bent at different spots so they can all fit together.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: December 27, 2019, 06:34:24 am
content: Relative to the plane of the coil, either case is still narrow eddy currents. Consider a single shorted turn, then think of a plate in the same plane: that would give "thick" eddy currents. (And a much longer magnetic path, because of all the air gaps between plates in the stack.)They do actually make them that way,http://www.epd-inc.com/2011/08/hypersil-cores/attachment/003/Efficiency can be higher because grain-oriented steel can be used. They're also made of continuous strip, wound into shapes (toroids and rectangles), glued, and cut apart into halves, a format also very handy for nanocrystalline materials (very pricey, but extremely low loss at mains frequency).Tim

author: excitedbox
author_rank: Regular Contributor
timestamp: December 27, 2019, 11:20:32 am
content: Yes I know. I was just trying to describe the orientation. I didnt actually mean that the eddy currents were thicker . That is sorta what I am talking about and I have seen those. I mean E core transformers like that one in your link. I have only seen E cores as flat laminates. Seems like you could save material too if you made them out of segments like that.
Punches for making pads for Manhattan? - Page 1
Forum section: electronics / projects

author: 0culus
author_rank: Super Contributor
timestamp: September 20, 2019, 01:10:18 am
content: I'm getting to the point where the projects I want to build are high speed/wideband enough that I need to be doing Manhattan style construction.What's everyone's favorite techniques and tools for making the basic building blocks?

author: MarkF
author_rank: Super Contributor
timestamp: September 20, 2019, 03:30:11 am
content: Some examples from Alan Wolke:Actually, this whole thread on the subject:https://www.eevblog.com/forum/beginners/copperless-perfboard-wire-wrap-for-rf-prototyping/

author: ChristofferB
author_rank: Frequent Contributor
timestamp: September 20, 2019, 06:03:49 am
content: A pair of tin snips are great for cutting square islands of pcb stock. A wide bladed hobby knife (that you can put more force on than an xacto) is also a must.Cyanoacrylate glue for sticking down dip packages and islands is a nice thing too.I would get some sheets of thin, 0.1 or 0.2mm copper foil stock. It's pretty cheap and let's you fold little shielding boxes to put over the most sensitive parts.

author: ledtester
author_rank: Super Contributor
timestamp: September 20, 2019, 06:34:55 am
content: I've used a hand punch like this:https://www.amazon.com/ABN-Power-Punch-Heavy-Duty/dp/B07D7HJQ5Z/ref=lp_2225057011_1_20?s=power-hand-tools&ie=UTF8&qid=1568961074&sr=1-20

author: German_EE
author_rank: Super Contributor
timestamp: September 21, 2019, 08:38:10 am
content: I have the same model of punch but mine was purchased about ten years ago from Harbor Freight and then a friend brought it across the Atlantic in her luggage. It makes good clean pads even now but you have to modify one side of the die to get rid of the locating bump or your pads will not be flat.As for the CA glue, this is what Dollar stores and Euro stores are for, that way a tube that hardens overnight will not be too much of a financial burden.

author: ledtester
author_rank: Super Contributor
timestamp: September 21, 2019, 08:55:54 am
content: Quote from: German_EE on September 21, 2019, 08:38:10 amIndeed, I got mine at Harbor Freight around that time, too. It's interesting that they don't seem to sell it any longer.

author: iMo
author_rank: Super Contributor
timestamp: September 21, 2019, 10:02:05 am
content: Quote from: German_EE on September 21, 2019, 08:38:10 amPut the tube into a small plastic zip bag, add silicagel balls.
Purchase of scope  - Page 1
Forum section: electronics / projects

author: electros6
author_rank: Regular Contributor
timestamp: November 28, 2014, 03:18:07 pm
content: Hi guys,I am now ready to buy the rigol DS1054Z 4 channel scope. Tell me your opinion about this scope or tell me if there is any better option.

author: calzap
author_rank: Frequent Contributor
timestamp: November 28, 2014, 04:10:29 pm
content: First, you should go to the test equipment forum and use the search feature; you'll find a lot. Second, watch EEVblogs 674, 675, and 683.Mike in California

author: rolycat
author_rank: Super Contributor
timestamp: November 28, 2014, 05:08:16 pm
content: Quote from: calzap on November 28, 2014, 04:10:29 pmAnd EEVblog 522. Probably 451 as well - many of the advantages of the new generation Rigol 2000 series Dave discusses in that video are shared by the 1000Z series.And maybe one or two YouTube reviews, such as Connor Wolf's assessment of the 1104Z.Quote from: electros6 on November 28, 2014, 03:18:07 pmWhether there is a better option for you depends very much on your budget, experience and requirements.

author: nctnico
author_rank: Super Contributor
timestamp: November 28, 2014, 11:30:50 pm
content: Take a look at the Siglent SDS2000 series as well if you consider buying the Rigol 1000Z. The SDS2000 is in a different price range but may offer features the Rigol 1000Z lacks.

author: CrashO
author_rank: Unknown
timestamp: November 28, 2014, 11:43:15 pm
content: Quote from: nctnico on November 28, 2014, 11:30:50 pmHas Siglent fixed their bugs since august? Last time I checked the SDS2000 series where pretty much in a pre-beta state, considering the firmware. The hardware is definitely great for the price, but how is their software at the moment?

author: nctnico
author_rank: Super Contributor
timestamp: November 28, 2014, 11:55:34 pm
content: Even with the beta firmware the SDS2000 is useable as a daily oscilloscope. I'm pretty sure Siglent will come up with new software which addresses the issues. They do that for their other equipment as well. The big question is when. It seems Siglent has a Christmas promotion for the SDS2000 series; it would be nice if they combined that with a new and much improved software version.
Purpose of additional pads in ST LQFP footprint - Page 1
Forum section: electronics / projects

author: Khaveer
author_rank: Contributor
timestamp: April 29, 2021, 04:35:10 pm
content: Recently while working with one of my nucleo boards I've noticed that there are additional exposed pads in each corner of the microcontroller's package. As far as I can tell ST adds them in every design that uses a LQFP64 package. I've checked the Altium files provided by ST and indeed those pads are a part of the footprint. There also two unplated holes placed under the package. Is there a specific reason why those are added? I'd guess it may be related to the production process but I have no idea why.The board I'm talking about is NUCLEO-F303RE.

author: bson
author_rank: Unknown
timestamp: May 01, 2021, 10:00:35 pm
content: I've used a number of ST LQFP64 ICs and never seen corner pads, so it's definitely not common... Are you sure the pads are on the package? Maybe it's for attaching a heatsink or something?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 01, 2021, 11:06:16 pm
content: The top pads may be fiducials. I don't know why they aren't symmetrical (round, concentric, square, cross, etc...).The thru holes might be vents or inspection?Sometimes you see relatively large (plated) thru holes under thermal pads -- usually for amateurs so they can be soldered by iron, or inspected.Tim

author: langwadt
author_rank: Super Contributor
timestamp: May 01, 2021, 11:22:14 pm
content: maybe they have a socket that fits the footprint

author: Khaveer
author_rank: Contributor
timestamp: May 02, 2021, 09:31:33 pm
content: Quote from: bson on May 01, 2021, 10:00:35 pmNo, the package is an absolutely normal LQFP64. The pads are only in the footprint on their eval boards.Quote from: T3sl4co1l on May 01, 2021, 11:06:16 pmThe package doesn't have a thermal pad so I guess it's not for soldering. I guess those could be vent holes, but I'm not sure why would they be needed.Quote from: langwadt on May 01, 2021, 11:22:14 pmThose commonly available sockets have quite a different footprint. It would have to be something custom. Or some sort of a debug/testing jig maybe?For a moment I thought that those extra pads could be used as a ground point when using a probe with a ground spring but in this case those pads are not connected to anything.

author: julian1
author_rank: Frequent Contributor
timestamp: May 02, 2021, 09:44:45 pm
content: The pads look like they would prevent traces being routed to inside the footprint, at least for the top layer. Hard to see how that could be anything but a limitation.

author: Yansi
author_rank: Super Contributor
timestamp: May 02, 2021, 11:39:16 pm
content: These are for fitting a ZIF socket for the LQFP package.