hybridfree/eevblog-posts huggingface dataset:
Two packages different thermal gradient/resistance issue! - Page 1
Forum section: electronics / projects

author: MT
author_rank: Super Contributor
timestamp: August 07, 2018, 02:58:56 pm
content: Assume 2 NPN transistors a oven and sensor on the same substrate in a SO14 package, then a dual NPN on same substrate in SOT23-6 package 26mm aside the SO14 driven by the oven heater signal. Both substrate heats up approximately at the same time (but not the packages) if sensor and heater located close to the 2 NPN's on the substrate cooling also are different between substrates and packages , SOT23-6 faster i reason. The startup heating is longer some seconds while the operating mode is "trickle heating" basically sensor into comparator with filter so heater becomes a a fluctuating voltage rather then heavy on off switching. Now how would you solve this so both packages have better and closer to equal heat/cool times? By adding a epoxy blob on the SOT23-6?

author: Detzi
author_rank: Regular Contributor
timestamp: August 07, 2018, 07:32:15 pm
content: What about getting four NPN in the same package if possible, and the oven seperate, then couple them thermaly and compensate for the delta in thermal conductivity in the oven package. What you describe is quite complexe and without fully revealing the "task" it's hard to say whats best or even workable. I would probably try to get an direct exposed die on all parts and coupple them thermally together.Adding something to match heat resistace may or may not work but is at least a lot of effort per device (no, or very costly mass production).

author: MT
author_rank: Super Contributor
timestamp: August 07, 2018, 10:26:08 pm
content: Quote from: Detzi on August 07, 2018, 07:32:15 pmWhat you say is to take the oven and sensor (they have to be on same substrate) and thermally couple that to 2-4-5-6-7-8-9 etc transistors in one ore more individual packages. Well i have thought of that , but i cant seem to find a viable heat distributor (vacuumed copper piper etc) that would work without leak heat a lot in the box or drawing excess power or as you noted end up being costly!Another problem with separating trannies and heater it response becomes very slow at heat up and a slugish to react tocooling effects , gradients increase.QuoteThe ultimate is to get all trannies on one die ofcourse but there is no such thing available and the one who had 5 trannies is EOL and insufficient!Actually its quite simple (theory) as described, a try to keep heating and cooling at same time period for both packagesnot making one or the other into lagging pattern which would affect the design of controlling currents.How much thermal resistance do a epoxi blob cause?
Two sided PCB production question. - Page 1
Forum section: electronics / projects

author: Pack34
author_rank: Frequent Contributor
timestamp: February 13, 2015, 11:56:36 pm
content: I've heard that when doing SMD assembly on a two sided board, you'll use solder paste with different melting points so that the first side doesn't fall off when you're reflowing the second. My question is, where do you find paste with different melting points? I'm not seeing this criteria mentioned on the usual suspects (Digikey, Mouser, etc)I've seen a single melting point solder paste used but with glue to hold the bottom components on. How does this work? Won't you need to stencil both the glue and the paste? Or are you just supposed to do a stencil and then manually go in and drop glue in the middle of all of the larger packages?

author: free_electron
author_rank: Super Contributor
timestamp: February 14, 2015, 01:24:20 am
content: no, that is not correct.the surface tension of liquid solder is high enough that parts , below a certain weight, won't fall of the board.in an industrial process the bottom of the board only sees a temperature below the actual liquidus point of solder. circuit board material is a relatively bad thermal conductor. and you can create a topside that is hotter than the bottom side.

author: rx8pilot
author_rank: Super Contributor
timestamp: February 14, 2015, 03:02:28 am
content: I do my 2 sided PCB's with all the heavy components on one side. Then I do the side with only small parts, followed by the side with bigger things like inductors. I have a convection batch oven and it seems to work ok.
Two SSIDs for a single Wifi module. Is it possible? - Page 1
Forum section: electronics / projects

author: VK3DRB
author_rank: Super Contributor
timestamp: July 10, 2017, 08:31:50 am
content: Hi.I am working on the hardware design of a device which will include a WiFi module. One of the requirements is the WiFi module will need to handletwodifferent SSIDs at the same time. The reason is for convenience - one SSID can be given to visitors and changed as required and the other SSID would be more permanent, used by the people who are not visitors.The product is high volume and price sensitive and the WiFi part has to be small, so I am not interested in a commercial router or some other bloated pretty-packed product. This solution might be a small off-the-shelf circuit board like a WiFi module having this feature. Another much less desirable solution might be tow have two networks, one at 2.4GHz and the other at 5GHz. Having two WiFi modules is more costly and two in the same band being so close to each other will likely cause problems.Maybe a module vendor out there might support two concurrent SSID's, or maybe they can modify their firmware accordingly. I simply don't know at this stage.Does anyone know how I can go about having a module that supports dual SSID's? Any help appreciated.

author: VK3DRB
author_rank: Super Contributor
timestamp: July 11, 2017, 01:37:33 pm
content: A big thank you to all those who took the time to respond. It IS very much appreciated. I will be researching each response over the next couple of days and will decide of which path to take. I owe you a beer.

author: cdev
author_rank: Super Contributor
timestamp: July 12, 2017, 01:51:20 am
content: Yes, you can do that with many OpenWRT compatible devices..This might workhttp://vocore.io/v1.htmland nowhttp://linuxgizmos.com/tiny-openwrt-wifi-module-updated-in-12-and-4-dollar-versions/The Vocore 2 lite OpenWRT wifi SBC is only $4

author: Harvs
author_rank: Super Contributor
timestamp: July 13, 2017, 10:17:08 am
content: Quote from: cdev on July 12, 2017, 01:51:20 amI can find plenty of media articles about it, but I can't see anywhere I can actually buy one, or say 1k of them @ $4?ESP8266's can easily be had for <$2USD each, and the SDK is pretty mature now. So two of those, or an ESP32 + ESP8266 might not be a bad solution if you need more processing power.

author: VK3DRB
author_rank: Super Contributor
timestamp: July 14, 2017, 07:13:33 am
content: Quote from: evb149 on July 10, 2017, 02:51:04 pmIt appears this is the way to go. Our processor will be an Arm Cortex A8 TI AM3352 Sitara, and the SDK is compiled under the same GCC compiler we are using. It ticks all the boxes for fast low risk development and features. This module is designed to work with our processor with minimal fuss. The cost is reasonable. Moreover the it supports up to 10 concurrent users. You are right, there is a performance hit with dual AP's and users and multiplexing with Bluetooth if we use that feature, but speed is not our concern in this application.A ripper of a solution!Eval board about to be ordered!
Two step-ups in serie (alcaline battery -> 5V / 24V) - Page 1
Forum section: electronics / projects

author: ixps
author_rank: Newbie
timestamp: February 21, 2021, 01:48:37 am
content: Hello.I'm designing a circuit that will be supplied by two battery rechargeable (2x1,5V=3V) and i need the two power supply's: 5V and 24V. The 5V rail will be supply logic (microcontroller, peripherals, etc) and the 24V will be supply my load (around 25mA).My question its:I design a step up to elevate the voltage of batterys to 5V using MCP1640. From this 5V, i will use AP3012 (step up also) to elevate this voltage to 24V.I never make thing so and i'm doubt if exist any problem in this topology.Thank you.

author: Zero999
author_rank: Super Contributor
timestamp: February 22, 2021, 08:03:45 pm
content: Why not use a microcontroller which will work off a wide supply voltage of 2V to 3V? That way you don't have to worry about 5V.Alternatively, how about just using a boost converter for 5V, but with a transformer, rather than an inductor, to give 24V? That way you don't need another controller and transistor, for the 24V.

author: Buriedcode
author_rank: Super Contributor
timestamp: February 22, 2021, 09:44:18 pm
content: There are plenty of small boost converters designed to power strings of LEDs ( up to ~30V) from 3V. Cascading boost converters is rarely a good idea, as the first will have to supply >150mA at 5V just for the second converter. The efficiency of a 3 ->5V converter, especially the MCP1640 won't be great at that current draw (which doesn't include the current required on the 5V line for other things).If you can find a boost converter that has reasonable efficiency for 250mA 5V out from 2-3V in, then as zero suggested, replacing the inductor with a coupled inductor will work. That way you have your 5V + 24V. You can get coupled inductors with ratio 1:4, or multiple winding ones with 1:1:1:1:1. So all of those in series, with the boost converter switching node on the first winding, and a diode/cap for 24V out on the last.But as coupled inductors can still be difficult to source, and are limited in package options (often either tiny SMT for <1W, or huge 30x40mm for >40W), I would just go with two separate converters both powered by the batteries. Maybe something like the AP3015https://www.diodes.com/part/view/AP3015?BackID=8171This also gives you control over the supplies with separate enable lines on the two converters.Whats the load on the 5V? And whts the load on the 24V?Edit: I have used the MCP1640 a number of times, and whilst they are quite neat in that some versions have true disconnect, they also struggle to provide >100mA @5V from 3V in. For loads 2-50mA they are fine though.
Two-switch forward current source is heating up when idle - Page 1
Forum section: electronics / projects

author: Artlav
author_rank: Frequent Contributor
timestamp: June 27, 2015, 10:26:08 am
content: I made a constant current power supply for an arc lamp, based on a welding inverter design.24V input, 8A at about 16V output.Transformer is a 40x25x11 ferrite ring.Problem is, it's heating up at no load, and is not heating up when loaded.Unloaded, it consumes about 1A, with the heat going out of the bridge's diodes and fets.As the thing heats up, it goes closer to 2A.Does not look like an overvoltage - nothing changes with the secondary disconnected from the rectifier, and there are no overshoots or problems in the bridge itself.So, is that a problem (it works fine and stays cool under load), and if so, what's causing it?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 27, 2015, 02:56:15 pm
content: Why use transistors 50 times larger than necessary? The gate charge is embarrassingly high, even for 50kHz operation. Without a voltage limit, I would guess it's running at full duty cycle and circulating current through the primary and burning losses in hard switching. This would be obvious on the oscilloscope.A current source is supposed to be shorted when not in use.Tim

author: Artlav
author_rank: Frequent Contributor
timestamp: June 27, 2015, 03:21:51 pm
content: Quote from: T3sl4co1l on June 27, 2015, 02:56:15 pmIt's the closest thing i had on hands...The driver can handle them, however - i see 200ns rise/fall times.Quote from: T3sl4co1l on June 27, 2015, 02:56:15 pmWhat should i be looking for?The controller can only give 50% DC.Quote from: T3sl4co1l on June 27, 2015, 02:56:15 pmThere is a time between it's turning on and the lamp getting ignited, where it should run into no load.Not a long time, but still.

author: Richard Head
author_rank: Frequent Contributor
timestamp: June 27, 2015, 05:54:07 pm
content: Have you confirmed that the magnetising current is a reasonable value?If you have a current probe clip it over the transformer primary and check the primary current waveform to confirm the transformer isn't saturating at full duty cycle.You could also just measure the CT secondary voltage I suppose.Also, the primary Shottkies for steering the magnetising current back to the bus can have a huge reverse capacitance that could be causing problems. You would definately need a current probe for that measurement as the current would be a shoot through current that the CT won't see.

author: DanielS
author_rank: Frequent Contributor
timestamp: June 27, 2015, 09:05:00 pm
content: Quote from: Artlav on June 27, 2015, 03:21:51 pmWhat to look for? Nothing, the circuit will look like it is operating fine except for the high idle power draw and dissipation in the core. The circuit uses current feedback and drives the primary however hard it needs to in order to reach the feedback current.If you want to reduce that wasted power, you need to add open-circuit detection that either resets the PWM into soft-start mode until a load is detected or lowers the current set-point/duty-factor until then.
two transistor on off switch--what is goind on? - Page 1
Forum section: electronics / projects

author: chimera_786
author_rank: Regular Contributor
timestamp: April 19, 2012, 08:17:39 am
content: Hello. So, its been sometime since I messed around with transistor circuits. I figured it'd refresh my knowledge. This is what I intended ( I have attached a schematic):I have wired up two transistors so that an led is always on when a push button is open. I have accomplished that with PNP transistor in a simple pass configuration. Now, the second transistor, an NPN, should only light up another led when the push botton is pressed and should remain lit till the time the button is pressed.I wired it up, but the thing is that, when i press the button, the pnp led remain on but dim and the npn led lights up. When I let the button go, the pnp leds becomes bright again and the npn led goes out (as intended).Where am I going wrong with this basic set up? I really am amazed how easy it is to forget basic transistors circuits (for me atleast)For image purposes, please see attached schematic. THANKS!!!!!!

author: cybergibbons
author_rank: Frequent Contributor
timestamp: April 19, 2012, 08:20:24 am
content: The current path for D1 is through D2 isn't it?

author: chimera_786
author_rank: Regular Contributor
timestamp: April 19, 2012, 08:50:16 am
content: Nevermind, I fixed it! YAY!!! It was a stupid mistake--> I was not biasing the base of the npn at all .. silly me. I have attached the scheatic of the correct version! Feel free to use and build upon for future needs.

author: jimmc
author_rank: Frequent Contributor
timestamp: April 19, 2012, 04:13:28 pm
content: Still not good I'm afraid.With the switch open the lower pole will be clamped to approximately 4.3v (5v - VBE) by the base-emitter diode of Q3.Disconnect the base of Q1 and look at the voltage at the junction of R3 & R5...Switch ON = 5(200/(200+1000)) = 833mVSwitch OFF = 4.3(200/(200+1000)) = 717mVNow 833mV is too low to guarantee turning Q1 hard OFF at low temperatures(More correctly I should say that 833mV behind 167ohm (200x1000/(200+1000)is too low to guarantee sufficient base current to saturate Q1)and717mV is too high to guaranteenotturning Q1 partially ON at high temperatures.VBEchanges by approx -2.5mV/oC so a 50oC step would change VBEby more than operating the switch.If you want to improve the margins of your circuit, try connecting R1 between the base of Q3 and the switch, change its value to 10k and also increase R3 to 1k.Jim

author: MikeK
author_rank: Super Contributor
timestamp: April 19, 2012, 09:36:34 pm
content: Why not just remove the connection between the bottom pole of the switch and the base of Q3?I missed that you wanted the second LED to stay lit until another press of the button.Dave has a recent blog episode where he uses a switch as a push-on/push-off.

author: chimera_786
author_rank: Regular Contributor
timestamp: April 21, 2012, 08:26:57 pm
content: Quote from: jimmc on April 19, 2012, 04:13:28 pmThanks for the heads up jim. I did tweak my values based on your suggestion and the transistors work the way they were intended.
Two USB power source for one board, and power sharing - Page 1
Forum section: electronics / projects

author: Watth
author_rank: Frequent Contributor
timestamp: April 28, 2025, 11:28:19 am
content: Hello EEV people!I am working on a board that has two USB C ports. It is based on a µCU that has 2 USB communications (one native, one through UART bridge). This means both could work as source or sink.So if one USB is powered (say by a PC or other USB power source), it should be able to supply power to the other (if plugged to a sink device).To have a unpowered bus powered by the otherh here is where I'm at now:Both VBuses are connected to aTPS2116power mux that powers the board, with priority for VBus1. (VBus2 is selected when VBus1 is < 4.75 V). That's the easy part.Now, to have one power the other, I plan to use, on each VBus, aAPX809S-44voltage detector 4.4 V difference. (could also be the 4.6 V version) with HIGH output when V diff is above threshold. Each controls an input HIGHAP22804Apower switch.What do you think of that design?Thanks for reading!
Two USB V source, how two feed one from the other? - Page 1
Forum section: electronics / projects

author: Watth
author_rank: Frequent Contributor
timestamp: April 25, 2025, 12:55:45 pm
content: Hey EEV people!A design has two USB connectors that are potentially connected t sources. When one is powered I want to power the other if the latter is not.I am planning on using aAP2192Adual power distribution switch, each channel controlled by two voltages comparator (2 channels chip, see note) (e.g.LM393).What I want to achieve: when a VBus is 4.5V higher than the other, the high one powers the other and vice versa.What do you think of this design?Note: The board will be powerd byTPS2116power mux, that means that if the comparator is double channel, it will be powerd whatever VBus is positive.Thanks for reading!
Two-Wattmeter, 3-Phase power measurement - Page 1
Forum section: electronics / projects

author: 741
author_rank: Frequent Contributor
timestamp: January 22, 2020, 10:31:06 am
content: WRT a 'star' (4 wire) system, the textbookFurther Electrical & Electronic Principlesstates that 3-phase power can be found by taking simultaneous measurements with just 2 watt-meters. Further:(a) Access to star pointnot required(b) Power for either balancedor un-balanced loadsis obtainedCalling the 3 phases r,b,g the picture in the book shows we measureVrb and Ir, Vyb and IyThat is, our common measurement node for voltage is the 'b' phase.However, the proof then seems to assume a balanced loadQuoteI looked this up online and found the followinghttps://www.newtons4th.com/wp-content/uploads/2010/03/APP014-3-Phase-2-Wattmeter-Explained.pdfNow this document statesQuoteThis would mean access to the star-pointisrequired.For a 4-wire 'star' 3-phase system with an un-balanced load and using the two-wattmeter method:Can I derive total load power?Is access to the Nuetral (Star) terminal needed?

author: coppice
author_rank: Super Contributor
timestamp: January 22, 2020, 11:29:23 am
content: The 2 watt meter approach does not work when you have a 4th wire (assuming the 4th wire is used for something more than instrumentation). The centre of the star has to be balanced. Most practical 3 phase watt meters measure the 3 phases separately, so they deal with any amount of imbalance. Its fairly unusual in the real world for a 3 phase load to be properly balanced. Even when the main load is something inherently balanced, like a large 3 phase machine, you'll find some lights and other accessories unbalancing the load.

author: SG-1
author_rank: Regular Contributor
timestamp: January 23, 2020, 05:51:27 pm
content: Here are some pages from my Introductory Circuit Analysis Textbook.In the medium voltage world nearly all three phase loads are balanced. This is where you would find this type of metering.See this explanation of 2 1/2 & 2 element watt meters:https://www.novatechweb.com/news/novatech-news-bryan-2-12-element-configuration/

author: 741
author_rank: Frequent Contributor
timestamp: January 24, 2020, 09:49:44 am
content: Thank you for the pdf excerpts. Since my interest is accurate measuring of 3-phase power with un-balanced loads, could I request the rest of section 21.13?I'll need to draw some phasor plots to properly see how/why fig 21.30 works, but it does at least 'feel' logical at this point.
Two way audio headset - Page 1
Forum section: electronics / projects

author: richcj10
author_rank: Unknown
timestamp: November 16, 2014, 06:31:43 pm
content: I am working on a intercom for two way communication in racing.Currently I have a master and pit crew parts done. They are attached below. The master interfaces with the car to get control signals form the steering wheel and tell the Telemetry system when a pit crew pack has requested a time stamp. (for marking the record for events)The driver was going to just have a simple skr and mic in the helmet. With a amp in the master unit. But the driver wanted it wireless. It allows him to get out of the car quicker if there was an issue.Does anyone recommend a short range wireless two way audio IC's?
TXL wire for 10A power cable to automotive gearbox ok ? - Page 1
Forum section: electronics / projects

author: Psi
author_rank: Super Contributor
timestamp: November 18, 2020, 08:55:51 am
content: I'm trying to change the wire used in an existing product.Currently it uses generic silicone rubber wire (AWG18) to send 5-10amps to a gearbox in an automotive environment.After doing some research I think the wire we should be using is TXL wire (XLPE).However I have a couple of questions someone on here might be able to answer.1) TXL is rated to 125C (not 200C like the silicone).I reckon this is probably fine, the gearbox in a car shouldn't get that hot. Do you agree?2) The insulation wall thickness of the TXL is less, it's 0.4mm, where as the current silicone wire is 0.8mm.I think this is probably fine due to TXL being XLPE.0.4mm of XLPE should be stronger than 0.8mm silicone. Do you agree?3) Ideally I want it to be flexible, so I will order the TXL AWG18 type that has more strands (41/0.16).Are there any disadvantages using wire with lots of small strands?4) Any other issues I might not have considered when moving from silicone to TXL ?

author: Ian.M
author_rank: Super Contributor
timestamp: November 18, 2020, 09:42:49 am
content: Many vehicles have a cooling system pressure relief cap with a 4 bar over-pressure rating. At 4 bar, water boils at approx 150 deg. C. I'd be worried about the wire temperature rating being exceeded on shutdown if the engine has been working hard immediately beforehand.

author: Psi
author_rank: Super Contributor
timestamp: November 18, 2020, 10:36:00 am
content: Fair point, although i'd imagine the gearbox gets less hot than the engine block.
TYN412 SCR Replacement - Page 1
Forum section: electronics / projects

author: TTENNEB
author_rank: Newbie
timestamp: May 27, 2023, 02:35:49 am
content: Fixing up a MIG welder with a blown AC motor driver, someone previously tried to fix it and totally destroid the PCB and handful of components along the way.The last part I need is a TYN412 SCR, anyone have some laying around or a compatable component?

author: DavidAlfa
author_rank: Super Contributor
timestamp: May 27, 2023, 03:26:15 am
content: It's just a 400V 12A SCR. Anything equal or better will fit.Nowadays the commons ones are 600/800V 12/16A.TIC126, 2N6397/8/9, 2N6400/1/2/3/4/5, BT138/9, BT145... Should be easy to source locally.

author: barshatriplee
author_rank: Regular Contributor
timestamp: May 27, 2023, 03:43:32 pm
content: You have already got some clues. If you wish, you can also post this question to the digikey forum.

author: TTENNEB
author_rank: Newbie
timestamp: May 28, 2023, 01:54:58 am
content: Thanks, all ordered. Fingers crossed it is the last faulty thing on the board.Already replaced the bridge rectifier, relays, all caps and a few resistors. PCB traces also resembled a war zone, pit marks from explosive copper vaporisation littered the board. Not a pretty fix but first major repair undertaken in 20 years. Diagnosed the initial fault to a dry solder joint on a resistor on the gas flow on/off circuit (nowhere near the area of damage after it was "repaired") looks like the high voltage from the welding transformer somehow made its mark on the main PCB.Geratly appreciate the help, after all the work I have put into it, didnt want to suff it up at the final component.
Type C HDMI Pinout - Page 1
Forum section: electronics / projects

author: macona
author_rank: Regular Contributor
timestamp: February 04, 2014, 09:34:37 pm
content: I am hitting my head upside a wall. I am working on making an adapter board for HDMI out on a camera and am using a Type C Mini HDMI connector. The problem is I am finding conflicting info on the internet on the pinouts. Some sites say +,shld,- and others say shld,+,- ordering.http://www.hardwarebook.info/HDMI#Type_C_Pinouthttp://pinoutsguide.com/PortableDevices/mini_hdmi_pinout.shtmlWhich is it? Anyone?

author: Monkeh
author_rank: Super Contributor
timestamp: February 04, 2014, 09:45:15 pm
content: http://www.hdmi.org/manufacturer/specification.aspx

author: macona
author_rank: Regular Contributor
timestamp: February 04, 2014, 10:35:44 pm
content: Thanks. I couldnt find the spec download link when I looked earlier.

author: ConKbot
author_rank: Super Contributor
timestamp: February 05, 2014, 11:50:39 am
content: Quote from: macona on February 04, 2014, 10:35:44 pmThats because you havent paid them $10,000 yet.Given the linear arrangement of the pins, and the fact that its a high speed serial signal, I'd suspect the one with the + and - signals next to each other and shields in between pairs would be correct. The other way would be hell for impedance and cross talk.The +, g, - arrangement makes sense on the larger HDMI cables as the pinout staggers as it runs down the connector so you have a differential pair next to a ground, and with a ground across from it, and the next differential pair is staggered diagonally from it.http://en.wikipedia.org/wiki/HDMII found some HDMI test fixtures looking for details on where the differential traces come from, but none of them showed a type C on a bare PCB.

author: amyk
author_rank: Super Contributor
timestamp: February 05, 2014, 11:59:00 am
content: Quote from: ConKbot on February 05, 2014, 11:50:39 amOr you didn't Google "HDMI specification PDF"It's shield, +, -.
Type K thermocouple calibration techniques - Page 1
Forum section: electronics / projects

author: gnx
author_rank: Newbie
timestamp: April 03, 2015, 11:54:23 pm
content: Hello experts,I am developing firmware for a TypeK thermocouple which uses ADC AD7193 for TC voltage. Another cold junction temperature sensor is used. I use the lookup table to convert CJ to voltage, add it to ADC measurement and then use NIST polynomials(10 coeff) to get temperature. On measurement using a calibrated TC simulator, the ADC was producing offset and gain errors leading to difference of 2-3 degrees in worst cases. I did a simple two point (zero and maximum voltage) calibration(zero offset removal and gain multiplication) and was able to get more accuracy. I simulated a few points and typical accuracy was about 1 degrees. My question is although there is no 'one size fits all', what is the standard procedure for doing TC calibrations? How many points over the whole range (-200 to 1372) would be tested and calibrated against?

author: retrolefty
author_rank: Super Contributor
timestamp: April 04, 2015, 12:46:27 am
content: Retired from instrumentation department of a large oil refinery, but our procedure was to do a five point verify/calibration check but not over the whole possible range of a K couple but rather over the range the sensor is going to be used in it's specific control loop, say 0-200 for a oil storage tank, etc. Actually we never considered thermocouples to be suitable for tight temperature control as the more accurate RTD sensors had come down in price over time Vs thermocouples and the total installed cost wasn't much different then a J or K couple.
type of ferrite bead used in multimeters? - Page 1
Forum section: electronics / projects

author: ftransform
author_rank: Frequent Contributor
timestamp: June 14, 2013, 12:29:39 am
content: So I was watching the 2015 teardown and dave pointed out the ferrite bead. Does anyone know what the ferrite bead material used there is?

author: c4757p
author_rank: Super Contributor
timestamp: June 14, 2013, 12:33:06 am
content: Ferrite?

author: ftransform
author_rank: Frequent Contributor
timestamp: June 14, 2013, 12:37:54 am
content: Quote from: c4757p on June 14, 2013, 12:33:06 amthere are many different grades with different impedances at different frequencies. I assumed the one that is used in a 6.5 digit meter will have a high attenuation of lower frequencies, to remove hf rectification errors.

author: ignator
author_rank: Regular Contributor
timestamp: June 14, 2013, 02:11:04 am
content: Quote from: ftransform on June 14, 2013, 12:37:54 amI'm going to guess that it's type 43. Very common material to use, and kicks in around 20MHz.My assumption is these ferrites were added after the original design for RE/CE compliance. Those long wires are real good antennas at picking of the internal clocks, and spraying this out to connected test wiring. The ferrite does a pretty good job of dissipating the RF on the wires as heat. I'm not aware of any regulatory reason to have them as input filters, but they serve that function also.

author: notsob
author_rank: Frequent Contributor
timestamp: June 14, 2013, 02:16:05 am
content: W2AEW did a youtube tutorial on this subjext

author: ignator
author_rank: Regular Contributor
timestamp: June 14, 2013, 12:00:10 pm
content: Quote from: notsob on June 14, 2013, 02:16:05 amThanks, now I have another site to spend time learning from.I'm not a RF guy (on purpose radio wave design, but digital/analog that had to work in that environment), and spent most of my career doing shake-bake testing. Ferrite's were used both to make the product robust to RS/CS, as well fix RE/CE.

author: ftransform
author_rank: Frequent Contributor
timestamp: June 14, 2013, 02:50:04 pm
content: this is why you should consider a ferrite bead for things other then EMI compliance. I suspect that keithley did this for this reason. Is there any ferrite that kicks in lower then 20MHz? Important for DC precision.http://www.analog.com/static/imported-files/tutorials/MT-096.pdf
type of lcd - Page 1
Forum section: electronics / projects

author: Mahyar-jafari
author_rank: Newbie
timestamp: February 26, 2018, 12:42:55 pm
content: hi guys,I have a lcd but I do not know what the model is. I'm sending a picture here.Please look at the picturewho has any idea what type is it ?

author: danadak
author_rank: Super Contributor
timestamp: February 26, 2018, 01:54:43 pm
content: Any markings on the part, on the underside of board or the LCDframe ?Regards, Dana.
type of mic meant to connect to a pc sound input - Page 1
Forum section: electronics / projects

author: snarkysparky
author_rank: Frequent Contributor
timestamp: December 11, 2017, 01:43:34 pm
content: Sorry , really really silly easy question.Does a pc port supply a voltage through a drop resistor for electret microphones.Is electret the type of mic that a pc port expects.I am making a circuit that inserts between a pc headset mic and the pc. So I may have to supply the dc bias, or not ??Google failed me on this, only got advertisements and "how to connect a mic to a pc" type sources.Thanks

author: danadak
author_rank: Super Contributor
timestamp: December 11, 2017, 02:17:51 pm
content: https://www.hobby-hour.com/electronics/computer_microphone.phphttp://blog.shure.com/computer-recording-fundamentals-2/Regards, Dana.
Type two compensator in flyback converter for LED driver in DCM mode.  - Page 1
Forum section: electronics / projects

author: Patrick66
author_rank: Regular Contributor
timestamp: March 03, 2024, 02:27:32 pm
content: Hello everyone, I would like to ask why is the type two compensator different from the error amplifier in the video (Figure is shown below) compared to Figure 1. Based on Figure 1, the Vo is connected to form a loop with Ve whereas the video in PE# 56 Vref is connected with Ve to form a loop. Is it the same? Thank you in advance.Video Link:

author: Terry Bites
author_rank: Super Contributor
timestamp: March 04, 2024, 02:44:03 pm
content: The error amp provides "proportional control" of the converter.But the converter has a complex phase and frequency response.To compensate for this you need to compensate the phase and frequency repsonse of the feedback loop.If you want to get into the nitty gritty of control loop compensation in LED supply read the attched. Yawn...
Typical Raspberry Pi power loads - Page 1
Forum section: electronics / projects

author: asgard
author_rank: Regular Contributor
timestamp: February 01, 2014, 05:12:41 am
content: I am planning to redesign an existing product, the SweetiePie, which is an HDMI and USB adapter for the Atrix 4G / Motorola 500 lapdock to the Pi. Part of this, originally, was to employ one of my Powah-1 modules to provide switching of the supplied voltage to the Pi. The Powah-1 can sink up to 1.4A, which is just barely enough to allow the Pi to boot up, but clearly more is required. My question is this - just how much current do I have to allow in the active switching to support most of the "likely" configurations. Wi-Fi is almost mandatory, as would be any number of add-ons. One of the most interesting, to me, is the HD LCD panel, fitted for the Pi expressly, plus providing addigional HDMI and USB hub support. That alone is going to require an additional 2A current loading, but I am trying to get an idea of what people "out there" are doing, and how much load current I would have to support, when the lapdock is used as a development workstation.Thanks, all.J.R. Stoner
Typical ON/OFF Transient Voltages from switching a DC Motor? - Page 1
Forum section: electronics / projects

author: LabSpokane
author_rank: Super Contributor
timestamp: January 27, 2015, 09:53:08 pm
content: I'm switching a small, 12V DC Motor (pulls approx 6W max) with a MOSFET that's rated to 60V IIRC. I realize that the MOSFET is tolerant of a certain amount of transients and I have overspecified it, but I'd like to toss in a snubber just for belt and suspenders sake.Before I risk blowing an input to my scope in ignorance, what is the typical range of transients that I might see - just as an order of magnitude?10's of volts?100's of volts?Should I fuss with a 700V differential probe on the front as an "insurance policy" against blowing an input? My scope is rated to 300V max on the inputs I believe.Thanks in advance.

author: tom66
author_rank: Super Contributor
timestamp: January 27, 2015, 10:04:38 pm
content: It depends entirely on the motor. The transient is caused by two things: back EMF and by the inductance of the motor.You would be able to easily eliminate this concern by placing a diode in reverse bias across the motor, which would absorb the meat of the pulse. Anything left would be determined by how fast the diode can begin conducting, and the inductance of the motor and diode leads, but is likely to be difficult to measure on a typical scope.I would honestly be more concerned about the MOSFET as most oscilloscopes are specified to withstand brief transients whereas a large transient can easily break the MOSFET. Usually drain source short but in some cases if you get a large enough pulse on the gate due to the drain gate capacitance you'll blow the gate source insulator and short across G-S.A quick look at my DS1074Z spec sheet says 1kV transients are acceptable although it does not specify duration or pulse rate.

author: LabSpokane
author_rank: Super Contributor
timestamp: January 27, 2015, 10:10:29 pm
content: Thanks. That's what I thought, and have always done with relay coils, but the motor switching is new ground for me.
u "micro" data acquisition unit - Page 1
Forum section: electronics / projects

author: mrjoda
author_rank: Regular Contributor
timestamp: April 10, 2017, 07:34:01 pm
content: Hello eevblog members,i would like to introduce you one of my new hobby project. Work name is simply uDAC. I had some LTC circuits in my drawer so... i want to test it. It is first version and i want to continue with this project and made some "adult" DAQ. NI DAQ are nice, but they are quite expensive and i need to educate myselfThis project will be open source, if it will worksBasic idea : take ADC, DAC, reference a put it in one board, isolated power supply and SPI interface.ADC is older, but still OK 24bit LTC2410DAC - LTC1650Main reference - LTC 6655 2V5SPI isolator - SI8662AB-B-IS1power supply DC/DC AIMTEC 5V to 2x7,2Vpositive supply rail LDO - ultra low noise high psrr LP38798SDnegaitve supply rail LDO - ADP7182A 5V fixed (very hard to find)Steps :1) Find,collect and solder all parts- DONE2) Do some long time stability measurements on supply rail and reference. Check electromagnetic emissions and noise spectrum on supply rail, tune supply filter.3) Write some test code to STM324) Do some stability measurements on DAC and ADC. Evaluate ENOB, errors, nonlinearity atc.5) Make some changes for better results.I will put results here. It take some time because i dont have GPIB controller and cable to my HP34401 so i must take it to my university lab.After all steps i post here altium design files, C test code and all results.At the end, excuse my english level i am not an native.

author: BFX
author_rank: Frequent Contributor
timestamp: April 13, 2017, 10:07:24 am
content: NiceOne PCB is waiting also on my deskI'm looking forward to see first results

author: mrjoda
author_rank: Regular Contributor
timestamp: April 25, 2017, 10:34:34 pm
content: so... after few first baby steps...i found small error in design. Signal marked as CS/LD at the isolated side (chip select) for DAC is connected to INPUT of isolator. I accidently swapped MISO and CS/LD and I didn't notice this mistake.I tried to easiest part - DAC.there are some results. I am going to do better measurements such as noise, long time stability, DNL, INL, ENOB, offset, transfer characteristic, maybe more. From results i want to modify an algorithm and try to set a correct requested value of voltage. Dinamic signal will be next level. This DAC is quite slow so generating signal is not primary purpose.
U shaped pinheader - Page 1
Forum section: electronics / projects

author: Steffen
author_rank: Regular Contributor
timestamp: May 27, 2016, 05:38:17 pm
content: Hi There,does anyone know where to find such U shaped pinheaders as shown below?I've seen such headers on PC motherboards as anchors for chipset coolers and wanted to use such headers for my PCB projects as anchor to put the GND-alligator clip of oscilloscope probes to. I've looked at Farnell, RS and some other distributors but I could not find anything. Previously I used some piece of bare straight wire which I bend and soldered to the ground plane.I would be very satisfied if one of the big distributors like Farnell, RS, Distrelec, Mouser, Digikey and so on would have something like that. I (or my employer) should be able to buy it very easily from Germany. That means some far east shops will not work for me.Thanks in advance for some hints and ideas.

author: AndyC_772
author_rank: Super Contributor
timestamp: May 27, 2016, 05:45:42 pm
content: Are any of these close enough?http://www.toby.co.uk/content/catalogue/series.aspx?id=6&Category=31

author: ovnr
author_rank: Frequent Contributor
timestamp: May 27, 2016, 05:54:58 pm
content: Here you go:http://www.digikey.com/product-detail/en/aavid-thermalloy/125700D00000G/HS400-ND/1216404Edit: Also, there's acheaper model too- I didn't bother trying to find out what thedifferenceis though.

author: Monkeh
author_rank: Super Contributor
timestamp: May 27, 2016, 07:06:21 pm
content: Quote from: ovnr on May 27, 2016, 05:54:58 pmThe 125800 is meant for thicker PCBs, the 125700 for standard 1.6mm. Not a clue why that makes it cheaper, though.

author: Steffen
author_rank: Regular Contributor
timestamp: June 21, 2016, 04:40:12 pm
content: Thanks for the hints. Digikey looks very promising. Usually I would only need types for 1.6mm PCBs. I will include that types in my next projects.Once I had to batch-adjust roughly 30 pieces of 19" eurocard (160x100mm) electronics where thesese would have been very practical if they were located at the middle of the board.
UAF42 Active Filter? - Page 1
Forum section: electronics / projects

author: rwgast_lowlevellogicdesin
author_rank: Frequent Contributor
timestamp: March 04, 2016, 11:41:01 pm
content: So I know A lot of people say this chip is no good for audio, but I have seen independent measurements on it showing much better figures than the data sheet claims. I would like to use this part to do an RIAA EQ stage in a phono pre-amp, now this might not work well, but it is an experiment. The problem is I dont really know much about active filters. This is a topic I am totally ignorant on, part of my reason for wanting to use this part at least in experimentation is it is easy to implement. My original idea was to use analog filtering, my issue is Im not really sure about how the UAF42 works, I know it has a LP, BP, and HP, and there all pretty easily implemented but can I just use it to do a multiple LP filters, etc?TI UAF42 datasheethttp://www.ti.com/lit/ds/symlink/uaf42.pdfI have a few of these around but there price has risen quite a bit over the years, If I have to use a bunch of them to hit this curve,then I may rethink this strategy quite a bit, even as an experiment. If it actually works well it seems like a much more precision part with less drift than using discretes, or am I wrong about that? Like I said I need to read some kind of good intro to active filtering, I have never designed an active filter. I understand and use op-amps I know what slew rate is and GBWP but I don't understand what the pole of an opamp is etc, Ive only used them as amplifiers, for control loops, and buffers.

author: retrolefty
author_rank: Super Contributor
timestamp: March 04, 2016, 11:51:34 pm
content: Never hurts to research before melting solder. Here is one source of background info on active filtering:http://sound.westhost.com/articles/active-filters.htmhttp://sound.westhost.com/articles/state-variable.htmhttp://sound.westhost.com/articles/gyrator-filters.htm

author: rwgast_lowlevellogicdesin
author_rank: Frequent Contributor
timestamp: March 05, 2016, 03:08:12 am
content: Oh awesome start thanks a ton! even mentions the UAF42
UART communication between 2.8V and 1.8V - Page 1
Forum section: electronics / projects

author: Aankur
author_rank: Newbie
timestamp: March 15, 2019, 02:13:51 pm
content: I want to establish a UART communication between two modules. The Rx/Tx Voltage levels of the modules are 2.8V and 1.8V. Also, I have only 3.3V as the supply voltage on my board.Kindly guide me as to how can I perform this level shifting.Thanks

author: oPossum
author_rank: Super Contributor
timestamp: March 15, 2019, 02:34:57 pm
content: 74LVC1T45
UART Communication between GSM and GPS - Page 1
Forum section: electronics / projects

author: Aankur
author_rank: Newbie
timestamp: April 24, 2019, 10:44:27 am
content: I want to establish a UART Communication between GSM and GPS.The Supply Voltage of GPS is 3.3V.The Supply Voltage of GSM is 3.8V.The measured RX/TX Voltage Levels of GPS is 2.8V and 0V (for logic High and logic Low).The measured RX/TX Voltage Levels of GSM is 1.8V and 0V (for logic High and logic Low).Since there is a difference between RX/TX logic levels of the GSM and GPS, So I amnot able to establish the UART Communication between GSM and GPS.I am using the interpreter of the telit GSM module to process the data of the GPS.I am not using any micro-controller to in between the GSM and GPS.Please suggest me a possible way to perform voltage (or Logic) level shifting.

author: tox3
author_rank: Contributor
timestamp: April 28, 2019, 10:10:17 am
content: GSM modules usually has output with 1.8V (for example VAUX/PWRMON on Telit LE910), ypu could use it to power level shifter ic.Not sure about GPS module though. Specific part number would be helpful

author: mikerj
author_rank: Super Contributor
timestamp: April 28, 2019, 01:27:57 pm
content: Have a look at thisTI app note.
UART ground loop maybe? - Page 1
Forum section: electronics / projects

author: enjoy.cowboy
author_rank: Contributor
timestamp: November 01, 2021, 12:10:28 pm
content: Possible murphy level 4 circumstance, but here's whats happening:I have this arduino talking to a modem over UART. The modem has a separate power circuit with a LM2596 converting from 2x Li-ion cells (7.4V ish) to 5V feeding into both the modem and the arduino. I built a hat on a perfboard to stick on top of the arduino to avoid any iffy contacts on a breadboard. I powered it on, plugged in the USB for serial debugging, no response from the modem via serial, even tho it is powered on and appearing to do something. I jiggle the hat back and forth a bit and to my surprise the AT commands start getting responses, so code is working fine. I let it go, thinking I found the sweet spot, no more responses. I jiggle it again, trying to pay attention to where I was touching, I was touching the power connections.Then I got my meter and started buzzing away. The power and ground connections from the batteries seem to buzz fine, also because the modem and arduino work on batteries alone. However, the arduino's USB plug seems to not have the shield connected to ground.Am I chasing a red herring here?

author: dtmouton
author_rank: Contributor
timestamp: November 01, 2021, 02:45:23 pm
content: Does the modem have enough time to complete its startup cycle, when switched on, before your Arduino start talking to it?

author: enjoy.cowboy
author_rank: Contributor
timestamp: November 01, 2021, 03:19:23 pm
content: Yup. When the iffy connection sweet spot is found, it works flawlessly. Its more of a contact issue than a code one.I found in the back of my drawer one of those Saleae usb logic analyzers. Thought about using it instead of the arduino serial monitor to avoid it being powered by the usb jack:Weird.... One of the lines seem active low while the other is active high?Upon further inspection of the modem TX line, it seems its just a contact bouncing? not an actual data packetModem RX looks fine...I got the meter and I measure a 0.7V drop between modem rx and ground. Just to be completely sure, it buzzes one way but not the other way around

author: dtmouton
author_rank: Contributor
timestamp: November 01, 2021, 06:00:19 pm
content: The only thing that comes to mind is that there might be a surface mount component that isn't properly soldered. They have a tendency to make contact when you push on the board. Otherwise the problem may be with one of your connectors. Also start at the lowest possible baud rate.