hybridfree/eevblog-posts huggingface dataset:
BGA module using purchased SAC305 solder spheres, anyone done  it ? - Page 1
Forum section: electronics / projects

author: glenenglish
author_rank: Frequent Contributor
timestamp: May 26, 2021, 04:38:47 am
content: I've got to do a small FPGA drop on module to reduce the tech on low end PCBs.Sure, I can do castellated holes perimeter. But castellated hole mounts do not perform well on thermal cycling, especially when they get big (say 50mm x 50mm)BGAs perform much better on thermal cycles than castellated holes, and better than LGA (land grid array) also, which is why mfr love them.ANyone done anything like this ? I was thinking of using some SAC305 spheres, and template stencil and dropping them onto the board with a vaccuum needle tip XYZ probe (PnP could do it, actually) . and apply heat... Maybe 33thou , designed for 1.27mm pitch BGA.
BGA pad tcream design help - Page 1
Forum section: electronics / projects

author: ETITsynthesizer
author_rank: Contributor
timestamp: May 31, 2020, 01:59:23 pm
content: I have been searching the internet for tutorials on the correct method for determining if I should use solder mask defined BGA pad footprint or if I should pull back the solder mask and use the other technique. I am also looking for information on the fenestrated pattern in tCream layer for the big square pad in the middle. I would like to read some technical papers about solder paste application thickness, min stencil opening etc.. I know some of this is dependant on the PCB fabricator. I do communicate with them. but before I go and ask them a lot of stupid questions I need some basic background information first. the design I am using now has 0.5mm ball pitch. the pads are 0.25mm diameter. the solder paste stencil (tCream) is 0.15mm diameter. the datasheet for this BGA part says 0.15mm or 0.8mm for tCream but it does not say why. they are labeled eee and fff. it does not dictate if the pads should be solder mask defined or not. point me to some tutorials or maybe even books I should buy.
Bi-directional 3v3 to 5V level translator (odd circuit)  - Page 1
Forum section: electronics / projects

author: Jester
author_rank: Frequent Contributor
timestamp: April 04, 2021, 10:48:49 am
content: I found this circuit while watching a video, I thought I would share.The CP_DIO signal goes off to a push button / display board and they save a pin by using SPI_MOSI for both writing andreadingdata.The SPIMOSI signal is read by the remote board on the rising edge of the clock and then sends back data on the same pin on the falling edge of the clock using an open drain driver. The FET is a 2n7002One way to do it I guess, looks like the parts add up to about $0.1

author: Miti
author_rank: Super Contributor
timestamp: April 04, 2021, 11:20:23 am
content: Take a look at this application note. I used this solution in one of my boards years ago and it works very well. IIRC I selected transistors with lower VGSt than 2N7002, but I guess it is not that critical.

author: HB9EVI
author_rank: Frequent Contributor
timestamp: April 04, 2021, 11:29:41 am
content: never tried that level shifter on SPI; on I2C it's working ufb, also with the 2N7002.

author: madires
author_rank: Super Contributor
timestamp: April 04, 2021, 11:47:06 am
content: https://circuitdigest.com/tutorial/bi-directional-logic-level-controller-using-mosfet(BS170)https://learn.sparkfun.com/tutorials/bi-directional-logic-level-converter-hookup-guide/all(BSS138)

author: T3sl4co1l
author_rank: Super Contributor
timestamp: April 04, 2021, 11:59:09 am
content: I've interfaced with displays that used a similar mechanism. In this case they usually name the pin SDA, and the direction is specified in the datasheet -- you must keep track of which byte you are on, whether it is legal to transmit. So, rolling that into a simple read() / write() function is a good idea.The circuit I used to interface that, was a 330 ohm resistor from MOSI to SDA, and SDA wired directly to MISO. The MCU always reads itself back (echo) during transmission; these bytes are discarded, of course. MOSI is set to Hi-Z during the receive frames, or the resistor does the job in case of accidents. (The resistor also serves as source termination; this is suitable for high speed communication as well, given a suitably matched value.)A little extra logic would be necessary for 5V compatibility, I suppose (presumably the pullup to 5V, and transistor, are used in this way in your example?). It should suffice to wire CP_DIO to a 5V-tolerant GPIO pin, or add a level translator (e.g. 74VHC50); a similar thing can be done for the transistor when greater speed is desired (the 10k and 2N7002 will have a nice gradual, what, few µs rising edge?).Tim
Bi-directional current source and DIY current clamp calibration - Page 1
Forum section: electronics / projects

author: dardosordi
author_rank: Regular Contributor
timestamp: June 11, 2019, 11:36:32 pm
content: Hi,this is my DIY current clamp calibration rig. It consists of a bi-directional current source built from a CRT vertical deflection IC (TDA4866) and a DIY 50-Turn Current Coil (Fluke 5500A clone).I choose the TDA4866 because I had a few lying around and its designed to drive a current through a coil. Being a full bridge chip means I just need a single supply (15V DC in my case).It can push 1 Amp RMS through my 50 turn coil up to a few KHz just fine.Here's the schematic and some pictures.PS: Big thanks to my lovely wife who wound the coil.
Bi directional electronic load  - Page 1
Forum section: electronics / projects

author: MadScientist
author_rank: Frequent Contributor
timestamp: May 11, 2021, 01:05:37 pm
content: I need to do some H-bridge testing and could usefully use a bi-directional electronic load , I could fashion one from pairs of mosfets etc , anyone know a reasonable priced existing one or failing that a schematic to studyThanks

author: NiHaoMike
author_rank: Super Contributor
timestamp: May 11, 2021, 01:20:28 pm
content: Add a bridge rectifier?

author: Nx-1997
author_rank: Regular Contributor
timestamp: May 11, 2021, 05:25:26 pm
content: If you had two 663XB power supplies, you could connect them in anti-series. Since each of these power supplies could source and sink current. This combination gives you a four-quadrant operation. This actually works, I just tested it with two 6632Bs.

author: MadScientist
author_rank: Frequent Contributor
timestamp: May 11, 2021, 08:13:44 pm
content: Err Not helping guys.

author: penfold
author_rank: Frequent Contributor
timestamp: May 11, 2021, 08:24:44 pm
content: When you say bi-directional, which quadrants do you need to operate in? Positive and negative voltage current sink, or current source/sink?

author: MadScientist
author_rank: Frequent Contributor
timestamp: May 11, 2021, 09:04:21 pm
content: Current sink only , quadrants 2 and 4

author: penfold
author_rank: Frequent Contributor
timestamp: May 11, 2021, 09:34:40 pm
content: I hate to bethat guy, but have you considered a resistive load bank or rheostat-type variable resistance?What kind of voltage and current are you targeting? Will the output voltage/current get smoothed or remain square at the switching frequency?

author: jbb
author_rank: Super Contributor
timestamp: May 11, 2021, 10:15:07 pm
content: Hey, I’ve been really happy with big resistor banks and mechanical switches for testing. They’re crude (coarse setting, tend to drift) but robust and effective.If using load at over, say, 30V DC, the problem is that you can’t turn a basic mechanical load switch off - it’ll arc.

author: thm_w
author_rank: Super Contributor
timestamp: May 11, 2021, 10:57:22 pm
content: Quote from: MadScientist on May 11, 2021, 08:13:44 pmWell you haven't provided any useful maximum specs:- Current- Voltage- Switching frequencyI assume most AC loads won't really work as they expect ~60Hz.
Bias Current Generation - Page 1
Forum section: electronics / projects

author: nikitagusev
author_rank: Newbie
timestamp: October 16, 2017, 06:02:43 pm
content: Hello,I want to generate a variable bias current for an IC from 5uA to 20uA. I am doing this with a TI current source and AD SPI programmable variable resistor, the datasheet set up and my schematic are attached in the pictures. Looks simple enough, I change the programmable resistance values through SPI and this changes the Bias Current.I supply 5V power to the PCB which is used to power most of the ICs on the board.Problem:When I connect the Vsupply (which is 3.3V generated by a TI LDO:http://www.ti.com/lit/ds/symlink/tps7a8300.pdf) to the current source by means of a jumper then there seems to be a short circuit.I assume that somewhere in my schematic I connected the ICs incorrectly because when I measure the resistance between the 5V line and GND I get 500Ohms. When I removed these components from the PCB the shorting problem went away.Thank you!
Biasing rf Transistor - Page 1
Forum section: electronics / projects

author: george79
author_rank: Contributor
timestamp: March 08, 2024, 07:54:11 pm
content: Hello,Im working on this project, it's a low frequency beacon around 500Khz with AM modulation. I want to replace the left side of the driver board and everything before the driver board. Im in the stage to connect the final amplifier that i did in the finals that want to keep them.two questions please.1) T202 transformer will be replaced, want to fit something equal, final preamplifier board han a TIP142 in class A and a transformer to have output at 50 ohm. Any ideas what type ferite to use and a path to start like turns ratio etc??2) My biggest problem, i want to add potentiometers to adjust the BIAS, i think it would be better to use an external power supply, and not the 50V like the schematic, please can you advice me please how to modify it please?Thank youGeorge

author: Terry Bites
author_rank: Super Contributor
timestamp: March 09, 2024, 10:44:34 am
content: seehttps://ludens.cl/Electron/RFamps/RFamps.html

author: george79
author_rank: Contributor
timestamp: March 09, 2024, 10:57:06 am
content: Thanks for the reply, very informative site!!But im a little scared what to choose, i was thinking if someone can help me to tell me what to do, or give me a path, because i dont want to make experiment and blow the finals.
Bicolor LED connected series/cascade - Page 1
Forum section: electronics / projects

author: John Anderson
author_rank: Contributor
timestamp: August 18, 2016, 07:38:28 am
content: Hi,I was wondering if exists a commercial bicolor, 3-lead LED with internal connection of the 2 LEDs in series/cascade, so by having connected the 'extreme' leads to +Vcc and Gnd, and applying a digital signal to the common lead, the LED directly lights up accordingly to the signal without the need of any external circuitry rather than the limiting resistor.Thank you!

author: ludzinc
author_rank: Unknown
timestamp: August 18, 2016, 08:59:10 am
content: A common anode Red / Green LED will work for you here.Use the one resistor on the anode, wire the green to ground. Wire the red to your signal pin.When the signal is high, Green will light. When low, Red will light (due to lower voltage drop across Red LED).
Bicycle computer magnetic sensor to USB to Android. - Page 1
Forum section: electronics / projects

author: KrisBendix
author_rank: Contributor
timestamp: March 08, 2015, 02:44:03 pm
content: Hi!I recently bought bicycle computer. Nice little thing. It has this magnetic sensor and little magnet on spoke that then gives signal.So I was thinking about some way to give that signal to android device trough USB and have an app that would act like bicycle computer... only better. May be even have rear view camera.Probably would need some kind of analog to digital converter and an actual android app.May be it already exists but I didn't find anything like that.Any ideas... suggestions?

author: Sirius631
author_rank: Contributor
timestamp: March 09, 2015, 05:24:48 pm
content: Instead of using a wheel sensor, Android cycling apps use GPS to calculate speed. This necessitates the need for higher capacity batteries for the phone, especially if you're also running a Bluetooth Polar HRM strap.A reed switch based wheel sensor is not as sensitive as a Hall effect device. The wires of wired sensors never lasted long, in my experience. You could possibly fit an Arduino Nano in the void of your handlebars to time the wheel rotation, convert that to speed and drive the USB, with the Android app handling the display. The handlebar void always struck me as a good place to house an extension battery power pack.

author: mark03
author_rank: Frequent Contributor
timestamp: March 09, 2015, 10:00:04 pm
content: I've sometimes wondered if the link between handlebars and wheel could be made using optical components, with the fork-mounted "transmitter" being battery-less. This would be an advantage over today's wireless computers, where you have to replace a battery in the transmitter. Some of them are also quite susceptible to RF interference.Would it be possible to come up with a design that "twangs" a resonant circuit coupled to an upward-facing infrared LED, every time the magnet goes by? The receiving end would then be tuned to the same frequency, like an IR remote control. Perhaps this could be built into the smartphone mount, and pass the raw data to the phone via NFC.

author: Nerull
author_rank: Frequent Contributor
timestamp: March 09, 2015, 10:08:55 pm
content: Garmin wheel sensors transmit in ANT+, which many phones can receive, and many more can use ANT+ receivers via USB-OTG. There is at least one Bluetooth wheel sensor out there as well.
Bidirectional 3.3v to RS232 level translator - Page 1
Forum section: electronics / projects

author: xuio
author_rank: Contributor
timestamp: June 11, 2015, 09:46:56 pm
content: Hi fellow forum members,I want to build an USB to RS232 converter with variable pinout. It will be part of a "smart" serial terminal server, which can adapt to any pinout and doesn't need any adapters.To do this, I need a bidirectional level shifter to translate 0/3.3V to +12/-12V, which are needed for RS232.I can't use a MAX232 with the TX and RX pins connected together (see attachment), because its output doesn't have a high impedance mode, and as a result always forces a state.I also can't use pullup/pulldown resistors, because the converter has to be able to work with high baud rates and long cables.A direction signal is available for each pin.Do you have any idea, how I can solve this problem?I can't wrap my head around this right nowThanks for your help,Moritz

author: oPossum
author_rank: Super Contributor
timestamp: June 11, 2015, 09:51:24 pm
content: Use a DG413 to switch between the RS232 transmitter and receiver.http://www.intersil.com/content/dam/Intersil/documents/dg41/dg411-12-13.pdf

author: xuio
author_rank: Contributor
timestamp: June 11, 2015, 10:14:16 pm
content: Quote from: oPossum on June 11, 2015, 09:51:24 pmThanks! That should do the trick.

author: LukeW
author_rank: Frequent Contributor
timestamp: June 12, 2015, 11:13:06 am
content: Quote from: xuio on June 11, 2015, 09:46:56 pmMAX242 / ADM242 / equivalent may also be an option to address this.
Bidirectional buffer with Better VOH and VOL - Page 1
Forum section: electronics / projects

author: Vcky_electro
author_rank: Contributor
timestamp: April 25, 2019, 06:51:10 am
content: Hi,Buffer need to be placed between below two ICs. their noise margin levels are in negative. Please suggest me the bidirectional auto detection buffer or level translator with which works on the below condition.In my case, margin levels are,Input IC's Vih min = 1.44V.output IC's Vohh min= 1.40V andinput IC's Vil max= 0.36Voutput IC's Vol max = 0.4V.Thanks,Vicky

author: ogden
author_rank: Super Contributor
timestamp: April 25, 2019, 08:17:58 am
content: What are those two IC's?

author: AndyC_772
author_rank: Super Contributor
timestamp: April 25, 2019, 08:23:51 am
content: To answer this question, we need to know the data rate and supply voltage(s) that are available.

author: Raj
author_rank: Frequent Contributor
timestamp: June 14, 2019, 05:44:10 pm
content: copy em-https://www.ebay.com/itm/5Sets-4-Channel-Bi-Directional-Logic-Level-Shifter-Converter-3-3V-5V-For-ArduiAB/153221534159?hash=item23acb711cf:g:xGQAAOSwVEBbrf3T
Bidirectional Current Monitor Fits ANL Fuse Holder - Page 1
Forum section: electronics / projects

author: croberts
author_rank: Regular Contributor
timestamp: March 17, 2013, 09:32:08 pm
content: The solar powered LED lighting system I designed for my home has a battery bank with (7) 84AH 12V sunextender batteries bussed together. When I did a topic on the system a while back I was advised by one of the very capable eevbloggers to fuse each battery individually. I took that advice and fused each battery with an ANL fuse. I decided to design a current monitor to fit in each ANL fuse holder. The current monitor uses a +/-50A bidirectional hall effect curent sensor made by Allegro and is fused with an ATO blade style fuse. I want a +/-15A current monitor so the ATO fuse is 15A and I’m using an interface circuit to scale the sensor output to 0v to 5v for a sensor output of 1.9v(-15A) to 3.1v(+15A) and then scaling again in software to display to the nearest 0.1A (-15.1A to +15.1A). The PCB measures 0.875" x 3.25" and has large wirepads spaced and sized to allow the PCB to mount on the ANL fuse holder threaded posts. One concern I had while designing the PCB was the current handling ability of the 2oz copper traces. Trace current calculators indicated I would be OK to 15A but I was still concerned. I’ve now tested the board to 14.8A and if the traces were warm it was hard to tell (approx 25C ambient). For testing, I have the interface circuit on a breadboard and I’m inputting the scaled sensor voltage into MS2 (PIC pin reconfigured as analog) on the master PDAC controller in my lighting system. It then goes via the lighting system network to a floating point LED display. Details of the network and display can be found at these topics;https://www.eevblog.com/forum/microcontrollers/a-full-duplex-network/https://www.eevblog.com/forum/microcontrollers/networked-rtc-fp-display/Attached are the following files;Current Monitor Schematic and PCB as pdfInterface Circuit Schematic as pdfPDAC schematic for reference as pdfDisplay Scaling Flowchart as pdfCurrent Monitor Testing Photographs
Bidirectional current monitoring with sense resistor and difference amp - Page 1
Forum section: electronics / projects

author: thmjpr
author_rank: Regular Contributor
timestamp: November 25, 2019, 06:40:38 am
content: I'm trying to measure the current through a sense resistor (0.1R) in both directions.I've found a few circuits using opamp + transistor or mosfet to translate the sense voltage onto an output resistor. This allows a simple way to drop the voltage down to a reasonable level to go into an ADC. Essentially the same as whats inside a high-side current shunt monitor likeINA168.Example with fet here:https://www.analog.com/en/technical-articles/upower-precision-dual-op-amp-combines-advantages-bipolar-cmos-amplifiers.htmlI can get the fet simulations to work OK with standard parts (micro-cap), but the built up circuit is not behaving the same way. Both outputs are at high levels, say 5V (about 0.3mA across a 15k resistor).This is the actual circuit:Opamp:MC34072Offset voltage: 0.5mV typ, up to 3mVInput offset current: 6nA typ, up to 300nAI would use two high side current sense amplifiers, but best I found is something like INA282:- Can only handle -14V common mode range, so needs protection if its going to be reversed- Bandwidth isn't great (10kHz)I could give in and switch to a precision difference amplifier. Theeasysmuuses LT1991 for example, but I'm not completely certain how that is sensing in both directions, as Vref is set at 3.3V and not mid rail.In my case its kind of nice to have the dual outputs (one for + current, one for -) as it doesn't cut ADC resolution in half.Anything obvious I'm missing here? I realize the opamp is not an ideal part, but I'm not sure yet if the issue is entirely from that.edit: I realize the FET feedback is going to the wrong input terminal in the schematic, will see if that resolves the issue tomorrow and update. Oddly in simulation taking it to the negative input pin seemed to work better.

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: November 25, 2019, 06:49:43 am
content: Hi,In a circuit like this one:The op-amp inputs are very close to the positive rail.It is essential that op-amps common mode input range includes the positive supply. The MC34072 does not. It only works if the inputs are between ground and more than 1.8V (at 25C) below the positive rail.Regards,Jay_Diddy_B

author: thmjpr
author_rank: Regular Contributor
timestamp: November 25, 2019, 06:57:54 am
content: Quote from: Jay_Diddy_B on November 25, 2019, 06:49:43 amThank you, so if I limit the output to +/-18V then it should be OK, at least in terms of Vicmr.I will do more testing tomorrow making sure I stay within thecommon-mode range, and see if the issue is present inside of that.
Bidirectional DC motor speed controller issue?! - Page 1
Forum section: electronics / projects

author: R2-B2
author_rank: Newbie
timestamp: January 28, 2020, 05:18:08 pm
content: Hi all,Trying to design a bidrectional DC motor speed controller for a pet project I'm working on. I've attached a circuit diagram below of what I'm working with. In summary:1. I've got a dual ganged 100k potentiometer which is the only input, one half controls the polarity that the motor see's and the other half controls the reference voltage that a comparator is looking at for PWM (If the polarity is +ve, then the wiper references the top terminal of the pot, and if the polarity is -ve then the wiper references the bottom terminal of the pot due to the arrangement of the transistors around the second half of the pot - so the total resistance seen from the pot is only ever 50k at it's midpoint and 0 at each extremity)2. There's a 555 timer built in as an Astable Multivibrator - making a roughly 50% duty cycle square wave.3. The output of the timer feeds in to an Integrator in the form of a ramp generator.4. The Integrator's output is then the Vin for the comparator.5. The comparators output then goes via a couple of transistors that feed into the bases of a transistor H-Bridge around the motor.My problem . . . it doesn't seem to work - nothing happens other than there being a slight smell of burning . . . I'm not an electronics expert by any stretch, but I can't suss where I'm going wrong. Would anybody be able to point me in the right direction? Really appreciate your help!
Bidirectional isolated switch circuit. Pitfalls? - Page 1
Forum section: electronics / projects

author: Dr_Neoo
author_rank: Contributor
timestamp: October 18, 2021, 06:42:41 pm
content: I have been looking into different kinds of solid state switches to replace relays in an application with 24V DC or AC signaling. While looking into different circuits i came across bidirectional IGBT switches based on using a diode bridge configuration.https://www.researchgate.net/figure/Diode-bridge-bi-directional-switch-configuration_fig5_258448391I exchanged this for an NPN optocoupler with an additional transistor for increased current handling and a quick simulation of the circuit (https://tinyurl.com/ydnp2p99) seems to show that the concept works.I'm kind of surprised to not have come across something similar before which makes me feel like I might be missing potential pitfalls? One obvious problem is the 2x diode and NPN voltage drop but this would no be a deal breaker in many applications.It will be interesting to hear your opinions on the circuit? Have you done something similar or do you see any potential problems with it?

author: David Hess
author_rank: Super Contributor
timestamp: October 18, 2021, 08:46:08 pm
content: In the past they used the same circuit to allow an SCR or bipolar transistor to control AC before TRAICs became available. Provisions need to be made for the optocoupler output transistor to handle high voltages.

author: Kleinstein
author_rank: Super Contributor
timestamp: October 18, 2021, 09:25:55 pm
content: I have used something similar with a triac too. At 230 V (maybe 220 at that time) the drop at the diodes is not so bad.For 24 V I would consider photo-mos switches or ready made solid state relays. IGBTs are not really the right choice at low voltage.

author: Terry Bites
author_rank: Super Contributor
timestamp: October 18, 2021, 10:45:49 pm
content: You can use a MOSFET instead of the trickier IGBT, they're are a bit crap at low voltages. You only get the dissipation benefits at higher voltages. It will almost cetainly be cheaper.Beware, leakage currents are a much higher than a relay will be, shockingly so.But then you need a serious relay to break DC. At least you can hear it turn on when you're not looking.
Big capacitors, any idea of value? - Page 1
Forum section: electronics / projects

author: KTP
author_rank: Frequent Contributor
timestamp: August 27, 2015, 11:43:32 pm
content: I am cleaning up my lab area and decided to break down a piece of equipment I had already robbed for some parts. This equipment was made in 1999 and has eight large Cornell Dubilier electrolytic capacitors in it (5000 UF 450V). These are screw terminal with a mounting stud part number DCMXE1264. I did find them on Mouserhttp://www.mouser.com/ProductDetail/Cornell-Dubilier/DCMXE1264/?qs=%2fha2pyFaduhv5ByvCaIG9xJAvBwBdsjKZfFu0%252bHNtf8%3dIt looks like they are pricey new ($90 each). They came out of a working power supply for a pulse laser and likely have very little use, but are 15 or 16 years old now.Any idea of the value? Worth selling?

author: calexanian
author_rank: Super Contributor
timestamp: August 28, 2015, 03:11:07 am
content: Not worth selling. Nobody wants used caps for commercial equipment. May be good for experimentation. Ring launcher, or magnetizer, or something of the like. Just hold onto them for the right project.

author: NiHaoMike
author_rank: Super Contributor
timestamp: August 28, 2015, 03:27:00 am
content: You'll have a hard time selling caps online since everyone is wary of counterfeits. If you do power electronics work, those caps are just right for a big inverter, such as for a DIY EV.

author: rickselectricalprojects
author_rank: Regular Contributor
timestamp: August 28, 2015, 03:37:37 am
content: make a big cap bank40000uf @ 350v is equal to 2.45 kilojoulesbe careful
big diode blow out - Page 1
Forum section: electronics / projects

author: funfairEE
author_rank: Contributor
timestamp: October 24, 2013, 11:59:43 am
content: At the moment I am repairing an old mobility scooter for my nan as a gift, I opened the charger to day just for a look inside and noticed that a component marked ZD2 had blown spectacularly(photo attached). I know it is probably some kind of zener diode. The half case I found for it inside the unit is marked C50 and 5C4, does any one have any clue as to what I should replace this with.Other than this the charger seems intact and clean, other than the bad construction, well cheep construction methods used like directly soldering on mains cables to the bored.Thanks for your help, ill be happy to provide more info if it is needed.

author: Jon86
author_rank: Frequent Contributor
timestamp: October 24, 2013, 04:41:42 pm
content: If you can't find what a C50 is, then you'll probably just have to work out what the zener voltage is from the components around it, have fun

author: mianchen
author_rank: Regular Contributor
timestamp: October 24, 2013, 05:37:35 pm
content: There's a ZD3 next to it, wouldn't it give you some clue?

author: funfairEE
author_rank: Contributor
timestamp: October 24, 2013, 05:54:17 pm
content: something to do with the voltage regulator that's near it to?This the same photo just not zoomed in on zd2. It is on the output side.

author: Neilm
author_rank: Super Contributor
timestamp: October 24, 2013, 06:06:44 pm
content: My first thought is that that is part of a snubber circuit. These circuits are used in topologies to control the peak voltage on the switching FET. If this is what the device is used for, then the FET might have been damaged. A failure like that means there could be damage to the rest of the circuit. If I am correct you will find it connects to a capacitor and resistor and will be in parallel with the primary winding of main transformer. Can you tell if this is the case?

author: funfairEE
author_rank: Contributor
timestamp: October 24, 2013, 06:11:59 pm
content: Quote from: Neilm on October 24, 2013, 06:06:44 pmIll check this tomorrow thank you.

author: funfairEE
author_rank: Contributor
timestamp: October 25, 2013, 02:36:11 pm
content: found the rest of the case for the diode, its a EIC BZX85 C43, zener voltage is 43v, hopefully should be able to replace it now, wonder if that will fix it or if there is another problem as well. But as always murphy will get me as always.

author: ivan747
author_rank: Super Contributor
timestamp: October 25, 2013, 05:09:35 pm
content: Get at least 10 of those zeners and be prepared to order more things as well. Zeners don't just blow up like that spontaneously, something else must be broken.
Big server SMPS spiking / surging on load removal question - Page 1
Forum section: electronics / projects

author: Chris Wilson
author_rank: Super Contributor
timestamp: April 29, 2017, 02:20:28 pm
content: I am curious as to whether uncontrolled voltage regulation on the drains of big FETs used in a push pull low frequency (136kHz) RF amp run in quasi Class D may be caused by the 52V at 57 Amps HP computer server SMPS not liking sudden load removal? I haven't the knowledge to test whether the uncontrolled voltage waveform when the drive to the amp is suddenly removed is from the antenna and loading coil, or from the PS. But from a max of 130V peak to peak square wave on the drains seen on my scope when running at 52V supply I can sometimes see the pretty uncontrolled waveform go beyond 400V before decaying. Could it be these SMPS can't cope with sudden load removal, and is there a way to minimize or fix it? My only thought was a secondary, permanent current draw in parallel with the 20 odd Amps the amp draws, maybe 10 Amps, but that's a lot of heat to dissipate. Any opinions welcome please. Thanks.

author: Chris Wilson
author_rank: Super Contributor
timestamp: May 05, 2017, 10:19:48 am
content: Great reply, thanks very much for going to such trouble. Further testing (by me, someone that is a bit out of his depth here...) suggest it's inductance in the output transformer that is causing it. The choke that feeds the centre tap of the output transformer (push pull output) shows about half the level of the disturbances on its transformer side, and pretty much sod all on the PS side. The drain sides of transformer show the most disturbance.Thanks again!!
Biggest cell capacity for 22 x 22 mm case - Page 1
Forum section: electronics / projects

author: Wilson__
author_rank: Frequent Contributor
timestamp: April 21, 2024, 03:42:18 pm
content: Appreciate some advises and insight to find a rechargable cell fitting 22 x 22 mm case. Would like to find a cell that is higher for bigger capacity, 100 to 300 mAh, with protection chip on cellWhich chemistry is best. Li Ion, Li Polymer or LiFePo4? TIA

author: wasedadoc
author_rank: Super Contributor
timestamp: April 21, 2024, 04:06:25 pm
content: Do you live in Flatland?(https://en.wikipedia.org/wiki/Flatland)Do you want a cell or a battery? You have asked about both but they are different things.

author: Wilson__
author_rank: Frequent Contributor
timestamp: April 21, 2024, 04:29:47 pm
content: Many thanks. Edited
Bike light driver/controller chip - Page 1
Forum section: electronics / projects

author: RobK_NL
author_rank: Frequent Contributor
timestamp: December 13, 2017, 08:17:06 pm
content: Hi all,I am looking into the possibility of hacking the front light on my bicycle, so some info on the driver/controller chip it uses would be helpful.Unfortunately, I have not been able to find anything yet. It's an 8-pin SOIC marked 1119A. It has push-button on/off control and also seems tohave the option for an LDR.Any idea where I can find a datasheet?Thanks.

author: phil from seattle
author_rank: Super Contributor
timestamp: December 14, 2017, 05:37:34 pm
content: Not much to go on from your post. Pictures might help. And "hacking" isn't very descriptive of your intent. WTF are you trying to do?Try tracing out the schematic and maybe some instrumentation (like current draw, LED Vf and such). From the context, it might become obvious what the chip is.
Bill of Materials Question - Page 1
Forum section: electronics / projects

author: tayexdrums
author_rank: Contributor
timestamp: July 10, 2010, 03:39:43 pm
content: I have searched all over the internet for the answer to this but I have yet to find any answer. Maybe someone will be able to help me=]I have built the PCB using the toner transfer method and it came out pretty good. All I have to do now is buy the components and solder it up. However, on the Bill of Materials list it calls for one 150K (Ra)* resistor. I do not know what the "Ra" means. There is also a call for one 1 uF/NP capacitor and I can't figure out what the NP means. I'm thinking it could mean non-polarized. I will include the PDF of the schematic, layout, and bill of materials.http://tonepad.com/getFile.asp?id=77

author: David
author_rank: Frequent Contributor
timestamp: July 10, 2010, 03:54:06 pm
content: RA = Resistor Array (Sometimes RN...)

author: tayexdrums
author_rank: Contributor
timestamp: July 10, 2010, 04:00:40 pm
content: So what does that mean? I think it is just a way of notation for that resistor.

author: David
author_rank: Frequent Contributor
timestamp: July 10, 2010, 04:08:44 pm
content: Is it just a single resistor? If there's multiple resistors in one package then that's a Resistor Array (or Resistor Network). However, if there's just a single resistor then its just down to the naming conventions used by the program.

author: tayexdrums
author_rank: Contributor
timestamp: July 10, 2010, 04:14:24 pm
content: It's the only resistor that has the Ra beside but its not the only resistor on the circuit board. I included a link to the PDF that has the schematic and layout.

author: RayJones
author_rank: Frequent Contributor
timestamp: July 10, 2010, 10:41:51 pm
content: If you read the description to your own linkshttp://tonepad.com/getFile.asp?id=77you will see Ra is a "Find on Test" style component, or more correctly you can change the behaviour by lowering its value.In this case speed up the decay time of the attack/decay aspect of the muting circuit.They even suggest a variable resistor by the schematic (as they do for the attack setting).the circuit will most likely work fine with a standard resistor in each location, but they are showing you can play around if you so desire.

author: tayexdrums
author_rank: Contributor
timestamp: July 12, 2010, 07:29:07 pm
content: Ohhh, I thought it might have been something like that. I read everything on the PDF but I just didn't put the two together. Thanks
Binary weighted AC current load - Page 1
Forum section: electronics / projects

author: Jester
author_rank: Frequent Contributor
timestamp: January 11, 2019, 01:10:46 pm
content: My patience for soldering multiple power resistors to create a high power ac load has run out, I always need one more resistor than required. So I’m going to build a binary weighted load. I welcome comments from anyone that has built one because as I’m considering myriad design trade offs, some compromise is going to be required.Ideal specifications:1) Voltage: prefer 0-250Vrms2) Current: 0-20A3) Closed loop4) 12 bits5) Power 500W6) Inexpensive ( stop laughing)Thoughts..........100W eBay power resistors are dirt cheap @ about $1-2 a piece.Switches:Initial thought was no or minimal # of relays, however triacs are going to be less than ideal with low input voltages, for example an audio amplifier or ac current source.MOSFET SSR’s are inexpensive for low currents (100ma@400Vp), above that relays are cheap, I’m just cringing at the thought of all that relay chatter when the current is adjusted. Realistically will rarely use at 240V, so hopefully 400V SSR is adequate.I will use an Arm with 12 bit A/D to measure V, I and calculate power dissipated to limit current when V is high.Cooling will use a couple of heat sinks fins to fins to create a tunnel with fan forcing air through the tunnel and out the case.Comments welcome.Sent from my iPad

author: soldar
author_rank: Super Contributor
timestamp: January 11, 2019, 01:37:38 pm
content: A series of about nine should cover what you need: 0.25, 0.50, 1.00, 2.00, 4.00, 8.00, 16, 32, 64You can build the resistors for close to nothing using nichrome wire from junked heaters.Why do you need relays and not use just manual switches? You need some kind of remote control?

author: capt bullshot
author_rank: Super Contributor
timestamp: January 11, 2019, 01:45:57 pm
content: Have you considered using a brigde rectifier in front of an electronic DC load set to R mode?Indeed, there are AC electronic loads available (but for sure rare on the used market).I've used resistors as AC loads, e.g. I have a set of four 30 Ohm resistors that I can connect in series or parallel (manually by rearranging the wires, still planning to make something up using relays), resulting in a 30 / 4 Ohm to 30 * 4 Ohm range. The resistors are "large open air" style wire wound resistors, so no need for a heatsink.See RHS at this picture:http://wunderkis.de/pwramp3/pic/test1.jpg

author: Jester
author_rank: Frequent Contributor
timestamp: January 11, 2019, 01:57:38 pm
content: Quote from: soldar on January 11, 2019, 01:37:38 pm---> 3) Closed loop

author: Jester
author_rank: Frequent Contributor
timestamp: January 11, 2019, 02:01:51 pm
content: Quote from: capt bullshot on January 11, 2019, 01:45:57 pmI should give the rectifier into the DC Load a try, however, my DC loads are lower voltage in the 60 -100V range, so that rules out --> 1) Voltage: prefer 0-250VrmsI'm not sure how well this method works with the diode drops and testing with low input voltage?
Binding post drawings - Page 1
Forum section: electronics / projects

author: sm_94
author_rank: Newbie
timestamp: April 13, 2024, 09:27:41 am
content: If anyone can upload or measure some quality binding posts as drawing in cad or even by hand, would greatly appreciate that. HP or phomona or fluke would be great, I will be making the same on lathe as soon as drawings are posted. Thanks.

author: DimitriP
author_rank: Super Contributor
timestamp: April 13, 2024, 09:49:30 am
content: ? ? ?https://www.mouser.com/datasheet/2/159/d3750_3760_3770_101_0-1513731.pdfhttps://www.mouser.com/datasheet/2/159/d4243_1_02-1514279.pdf
Bingo flashboard Neopixel retrofit - Page 1
Forum section: electronics / projects

author: Galane
author_rank: Newbie
timestamp: January 19, 2022, 02:36:55 pm
content: The local Elks lodge has an ancient Bingo King flashboard. Looks exactly like this one.https://www.worthpoint.com/worthopedia/vintage-bingo-king-machine-automatic-308807258There are zero electronics in it, it's all "brute force" wiring where each ball hole on the board has a lever microswitch with a wire that directly connects to a lamp on the flashboard. There's 75 controlled lamps on the board and 5 that are always on for the BINGO letters up the left end. There's at least 77 wires in the fat cable connecting the console to the flashboard, assuming just one ground wire.I'd like to replace the 28 volt BA9S bulbs with LEDs but can't find any for sane prices. The companies that make these flashboards will happily sell people white LED BA96 bulbs, for $4.50 each. $360 to replace all the bulbs is a no-go.I've been thinking that a pair of Arduinos or the cheaper Raspberry Pi models would be ideal for this. One in the flashboard to run 80 Neopixels and one in the console to read all the switches and communicate which ones are on to the flashboard controller over a simple cable with a few wires for power and data.The sticking point is how to read 75 or more switches that could possibly all be on simultaneously? Not that it's very likely that a game of blackout would ever go to 75 numbers, but the capability has to be there.I say or more because other switches would be needed for some additional features. With Neopixels and Arduinos or RPi it would be possible to have color animations triggered by the operator with a button press.For a less ambitious way of doing it, how about reducing the 28VDC going to the flashboard so that the quite inexpensive 6V BA9S white LED bulbs available for retrofitting pinball machines could be used? I figure there's a 120VAC to 28VAC transformer in the console and a bridge rectifier.

author: Martin Miranda
author_rank: Regular Contributor
timestamp: January 19, 2022, 02:55:00 pm
content: for the switch scanning you need diodes per switch.it's the same circuit for scanning any switch matrixes.

author: Martin Miranda
author_rank: Regular Contributor
timestamp: January 19, 2022, 02:57:43 pm
content: you can use RS-485 for data. but for power it's better to have a separate power for the display board and switch panel.
BIOS Programmer -> 25Q16BV Code Dumped In 25Q64FV [ Not Working ? ] - Page 1
Forum section: electronics / projects

author: Amarbir[Lynx-India]
author_rank: Frequent Contributor
timestamp: August 29, 2013, 06:10:56 pm
content: Hi ,Today I Came Across a Levono S10-3C Laptop .The Motherboard would not post .Well after opening the laptop up and taking the motherboard out i figured out all supply voltages were ok so i though the BIOS is bad .I took the BIOS chip out The Same was a 16Mbit " 25Q16BV " .Tried Reading it on the BK Precision 844USB Aka Elnec Smartprog2 Programmer but it would give pin 8 error and not read the same .Damn i thought the chip is fried .Tried the same on the Sofitech SP8-A " Same Issue " .I had access to a gigabyte desktop board and i took out the b_bios from the same .B_bios is backup BIOS of the desktop motherboard .This was a 64Mbit Version " 25Q64FV " .Well i erased the same And Took it To a Friend of Mine Who had The Lenovo S10-3C BIOS With Him And He Flashed The Same For Me .This Means 16 Mbit Code Into 64 Mbit BIOS .Yanked it Back into the Board " Did Not Work " ,Well Damn i though let me take the board to him "Also left the supposedly dead older BIOS Chip 25Q16BV " .After a Few Minutes He Tells Me That he Has Flashed / Programmed My "Supposedly Dead Chip " And The Board is Posting Damn What The Hell ? . I Got The Board Back Took The " Supposedly " Screwed BIOS Chip Out of It Read It Again " Same Bloody issue pin 8 Error " . Switched Off The Manufacturer And Contact Pin Check of Programmer Read The Same And Programmed It Back In 64 Mbit BIOS Thinking Now My 64 Mbit BIOS Chip Will Post "Well It Did Not " .Questions Are1 : Will The 16 Bit BIOS Code Flashed into The 64 Mbit BIOS Chip Not Work ?2 : How The Hell Does The Bad 8 Pin Contact Chip Work in The Motherboard " How Come "I Am Going Crazy
Biphasic Pulse Generator - Page 1
Forum section: electronics / projects

author: otaylor
author_rank: Newbie
timestamp: September 26, 2019, 03:45:49 pm
content: I would like to build a biphasic pulse generator with 2 outputs which is controlled by an Arduino Nano. It should be able to output +/- 10V with a maximum current of 10 mA. The shortest adjustable pulse length should be 1 ms.I attached the schematic I figured out so far. I'm basically using a 2-channel DAC, whose signal is amplified + shifted by an OpAmp in a differential amplifier configuration. I'm using a DC-DC converter to generate +/- 12V.Do you think my schematic is fine so far or are there other details you would improve?Thanks a lot!
biphasic stimulator design using a constant current source and a microcontroller - Page 1
Forum section: electronics / projects

author: boriskorbel
author_rank: Newbie
timestamp: May 19, 2020, 08:44:25 am
content: Hello guys, I want to design a stimulator using a constant current source and digital potentiometer controlled by a microcontroller for setting the current level. I want to use H bridges to implement the biphasic function (see proposed schematic in an attachment).I will be happy for any comments on the scheme and the correctness of the circuitry connection. Tho I would like to stick to the components mentioned in the schematic.

author: SiliconWizard
author_rank: Super Contributor
timestamp: May 19, 2020, 02:58:11 pm
content: Just took a quick look so far. A couple remarks. First a question: what are your requirements? (output current range, max voltage compliance, acceptable leakage current when off, min rise and fall times...)The remarks:* Not sure how you envisioned to use the DRV8837 as a constant current source? Can you elaborate?* A few parts (like amps/opamps) on your schematic have symbols that are just boxes and make it hard to read. You should use traditional symbols instead, that would make your schematic a lot more readable. As it is, it's pretty hard to guess what it does without a lot of mental exercising.* Likewise, too many labels IMO. I'm personally not against labels to unclutter schematics (some people hate them), but here some of them don't help readability either.IMHO, poor readability makes it hard to help you, and may be a reason why you didn't get more answers so far.
Bipolar ADCs and references - Page 1
Forum section: electronics / projects

author: ovnr
author_rank: Frequent Contributor
timestamp: March 22, 2016, 11:24:35 am
content: So I've found myself abitout of my depth. I'll be using aMAX1127024-bit ADC for a project, and I'll be running it in bipolar mode with ±1.8V supply rails.Now I'm not 100% sure how to deal with the reference input? It's differential (REFN and REFP), and my plan was just to throw a 2.5V ref between AVss and AVdd, tie REFN to AVss and REFP to the 2.5V reference. Iexpectit'll "just work" and give me a ±1.25V input range relative to ground. Am I mistaken? Any other pitfalls?(Ireallywouldn't like a -1.8V to +0.7V input range to suddenly manifest itself.)

author: danadak
author_rank: Super Contributor
timestamp: March 22, 2016, 01:21:44 pm
content: Datasheet is not clear about that, but seems to infer that running onsplit rails, and a ref tied between the the Refp & Refn pins that willwork as you expect.Regards, Dana.

author: suicidaleggroll
author_rank: Super Contributor
timestamp: March 22, 2016, 05:30:32 pm
content: According to the datasheet, in bipolar mode, the input range is -Vref to +Vref. With a 2.5 Vref, that gives an input range of +/- 2.5v, not +/- 1.25v.

author: ovnr
author_rank: Frequent Contributor
timestamp: March 22, 2016, 06:57:11 pm
content: Quote from: suicidaleggroll on March 22, 2016, 05:30:32 pmAh, but according to common sense, it's not. The part is limited to 3.6Vandhas a suggested Vref of 2.5V. That just won't work if you expected a 5V input range.In any event, studied the EVM schematics a bit more, and it seems like I was right re: connecting the Vref ground to AVss.

author: Alex Trofimov
author_rank: Contributor
timestamp: March 23, 2016, 10:55:57 am
content: From the datasheet:"The ADC input range is programmable for bipolar (-VREF to +VREF) or unipolar (0 to VREF) ranges. The U/B bit in the CTRL1 register configures the MAX11270 for unipolar or bipolar transfer functions."And this drawing took my sight.I took just a breaf look, don't really have time to look deeper. :-) Hope, it helps