hybridfree/eevblog-posts huggingface dataset:
Drive a sharp LCD by TOSHIBA chip - Page 1
Forum section: electronics / projects

author: wiwiwi
author_rank: Newbie
timestamp: August 29, 2019, 10:10:57 am
content: Help Please,Now I have a sharp LCD (model: LS055T3SX05) and a THOSHIBA chip (TC358870XBG).But first of all, I want to light up the LCD. From what I read there are three pins (LED+, LED-, LED_PWM) related to backlight.I apply 5v to LED+ with 0v to LED-, for LED_PWM I am using the 3.3v blue pill (arduino) to produce pulse. However, Backlight is still not working......anyone can help? appreciated!!!!!

author: wiwiwi
author_rank: Newbie
timestamp: September 03, 2019, 05:06:44 am
content: help pls!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

author: oPossum
author_rank: Super Contributor
timestamp: September 03, 2019, 05:17:19 am
content: Backlight is 6S2P so it's not going to run on 5V.

author: wiwiwi
author_rank: Newbie
timestamp: September 11, 2019, 06:52:58 am
content: But weather this LCD need to be driven by code (like power on sequence) with a MCU or direct voltage can light up the LCD?I found there is a information say "POWER ON sequence, power off sequence, video mode sequence" in the lcd document, so that I wonder this lcd need MCU to drive.

author: ealex
author_rank: Frequent Contributor
timestamp: September 11, 2019, 02:10:29 pm
content: it would help us if you attach a datasheet fro the display - I've tried looking for it and it does not seem readily available.the backlight has 6 leds in series and no back-light driveryou'll need to supply at least 18V, current limited to ~ 20mA for startabout how to initialize the display - no clue without a data sheet

author: wiwiwi
author_rank: Newbie
timestamp: September 13, 2019, 01:46:32 am
content: Of course, here we go.I am quite confused weather the mipi lcd can power on backlight by supplying voltage directly without any code or power sequence?thanks, bro.
Drive high side mosfets with low side driver? - Page 1
Forum section: electronics / projects

author: Deadpixel732
author_rank: Contributor
timestamp: August 24, 2013, 10:09:40 pm
content: Hey guys,I have a question.If I wanted to drive a 4 N-Channel H bridge with a UCC27525 (Dual 5-A High-Speed Low-Side Gate Driver), could i do it (supplying 12v to vdd of chip) even though the chip is classified as a "low side gate driver". 12V is within the power limitations of the UCC27525 and would be enough voltage to successfully switch my mosfets (CSD16342Q5A) highside with a 5v load so it seems like it should work. My guess is that its classified as a low side driver because of the relatively low vdd voltage limit compared to other high side drivers that can handle 100v+. Or maybe there is some other huge difference im missing.UCC27525 datasheet:http://www.ti.com/lit/ds/symlink/ucc27524.pdfCSD16342Q5A datasheet:http://www.ti.com/lit/ds/symlink/csd16342q5a.pdf

author: Marco
author_rank: Super Contributor
timestamp: August 24, 2013, 10:20:04 pm
content: It's a low side driver because it drives the gate to ground to turn the MOSFET off, a high side driver drives Vgs to 0 ... if your power supply for the bridge was >8 Volt you would be exceeding min Vgs when turning off the high side MOSFET.

author: johansen
author_rank: Super Contributor
timestamp: August 24, 2013, 10:27:21 pm
content: well the gate should be able to handle +/-20 vgs so it would work,why you would bother i don't know, a five volt load means you've got hundreds of high and low side drivers, many that can handle 5 amps of gate drive just fine.what are you driving that needs 5 amps of gate current?

author: johansen
author_rank: Super Contributor
timestamp: August 24, 2013, 10:51:06 pm
content: Quote from: Deadpixel732 on August 24, 2013, 10:09:40 pmyes, high side drivers are floating and most of them are powered by a bootstrap capacitor and a diode, they also have a level shift network involving pulse generators... take a look at the datasheet.

author: Deadpixel732
author_rank: Contributor
timestamp: August 25, 2013, 12:37:32 am
content: Quote from: johansen on August 24, 2013, 10:27:21 pmWell actually I just need any mosfets driver that can drive the mosfets ive linked highside (with 5v load), be able to switch at around 750kHz to 1Mhz, and have one of its outputs inverted.I anyone could, I would really appreciate a few recommendations.Thanks.
Drive NOKIA 5800 LCD - Page 1
Forum section: electronics / projects

author: FAMELC
author_rank: Newbie
timestamp: December 29, 2019, 06:59:35 pm
content: Hi.I want to drive NOKIA 5800 LCD with microcontroller but my problem is pinout details of LCD connector.I mean, I have no documents or datasheet of it to undrestand about timing and protocol of LCD pins.I also downloaded the relevant files like "Nokia service manual"(LCD pinout attached), but i cant undrestand CDP0 ck- or CDP0 ck+??Why positive and negative is used??Thanks a lot.

author: coromonadalix
author_rank: Super Contributor
timestamp: December 30, 2019, 12:06:18 am
content: Some talks over there :https://www.raspberrypi.org/forums/viewtopic.php?t=46413

author: Prehistoricman
author_rank: Regular Contributor
timestamp: December 30, 2019, 03:04:58 am
content: Quote from: FAMELC on December 29, 2019, 06:59:35 pmPossibly LVDS (low voltage differential signals). One wire uses positive logic while the other uses negative logic.

author: FAMELC
author_rank: Newbie
timestamp: January 01, 2020, 07:55:21 am
content: Thanks for answerWhat is the voltage level for each pin?
Driver circuit schematic for a 40kHz/60W ultrasonic transducer - Page 1
Forum section: electronics / projects

author: amp_architect
author_rank: Newbie
timestamp: August 13, 2025, 04:51:39 pm
content: Hi all, I am making a DIY probe type ultrasonicator which I will be using for food samples. I will be attaching the transducer to a metal probe and I will need a driver circuit to excite it. I was thinking of either using a PWM signal (through a arduino) or a sine wave (sine wave generator circuits). I figured out using a square wave would be counterintuitive for my purpose as it would generate harmonics. Is there any preexisting circuit/schematic that would match my purpose? Thank You!

author: MariuszD
author_rank: Regular Contributor
timestamp: August 17, 2025, 07:26:21 am
content: Applying a square wave to a transducer is a bad idea, but a square wave is easy to generate. In practical implementations, a square wave is applied to an LC circuit consisting of a transformer and a transducer. The LC circuit must be tuned to the transducer's resonance. There's only a sine wave on the transducer.Example of an ultrasonic cleaner diagram.https://www.edn.com/teardown-reverse-engineering-an-ultrasonic-cleaner/For amateur experiments, it's better to build a low-voltage push-pull circuit.
Driver for ILC1-1/8L - 8 segment display - Page 1
Forum section: electronics / projects

author: MikeJazz
author_rank: Newbie
timestamp: February 04, 2017, 03:32:28 pm
content: Hello everyone,I was hoping to get pointed in the right direction about a driver for a rather large VFD.Its one of these of eBayhttp://www.ebay.co.uk/itm/201481193515?_trksid=p2057872.m2749.l2648&ssPageName=STRK%3AMEBIDX%3AITIt has got the following specsVoltage of filament - 3,15VCurent of filament - 162mADC grid voltage - 35VDC voltage on anode segments - 35VCurrent of anode - 150mACurrent of grid - 100mAAnd it has a rather large current draw for the segment compare to other VFDs. As i read it its 35V at 150mA.So here is the question. Does a driver exist for that level of current.Any and all recommendations will be appreciated.- Mike

author: Ian.M
author_rank: Super Contributor
timestamp: February 04, 2017, 03:44:07 pm
content: Microchip'sMIC29818 bit high side driver should be able to handle it easily, with a 33K pulldown resistor on each output.

author: MikeJazz
author_rank: Newbie
timestamp: February 04, 2017, 03:50:32 pm
content: Thank you Ian, this is indeed what I was looking for.
Drivin' a Sony LCD Viewfinder - Page 1
Forum section: electronics / projects

author: brobbuilder
author_rank: Contributor
timestamp: October 15, 2015, 02:26:09 am
content: Hey yall,I found this old LCD viewfinder (Sony LCX058AKC) in a broken old camera and I want to use it with one of my projects to make a kind of pocket camera tester. It would be neat to use it for FPV as well. I have a clean source for NTSC video, which I want to display on the LCD. These EVFs are good for what they do and I can't find any newer ones online for less than $100.The LCD datasheet says "This panel provides full-color representation in NTSC/PAL mode" and "NTSC/PAL compatible". Does this mean I can just feed the NTSC output from my processor into one of the pins?I have an FPGA and 8-bit ADC but I'm not sure if they're necessary.Thanks yall. Datasheet attached.

author: brobbuilder
author_rank: Contributor
timestamp: October 15, 2015, 03:26:39 am
content: It's looking like it doesn't accept analog NTSC.

author: amyk
author_rank: Super Contributor
timestamp: October 15, 2015, 03:47:01 am
content: It's an analogue RGB LCD, you'll need to find/create a timing controller for it to output signals according to the datasheet. When it mentions NTSC it just means that the timing (horizontal/vertical rates) and resolution is compatible.

author: Richard Crowley
author_rank: Super Contributor
timestamp: October 15, 2015, 03:49:05 am
content: It doesn't accept digital video (HDMI, SDI, etc.), either.It requires a separate circuit to decode the video signal (analog or digital) and feed red, green, and blue pixels to the display.Ben Heck did a video on interfacing to LCD panels like that.It is not a project for an amateur. Even someone with lots of experience will spend days or weeks hacking a driver circuit.

author: brobbuilder
author_rank: Contributor
timestamp: October 15, 2015, 05:48:52 am
content: Thanks for the assistance all. I think I'll work on a smaller display first (64*48 monochrome) and see if I can jump up to this one.
Driving 2x Hewlett-Packard HDSP-6508 over i2c - Page 1
Forum section: electronics / projects

author: Lomax
author_rank: Frequent Contributor
timestamp: February 24, 2019, 05:24:13 pm
content: I'm working on a mock-up "submarine" exhibit for a public exhibition, which I want to fill with bits of surplus aviation/military gadgetry (because surplus "submarine" gadgets are rare & expensive). Most of this will be completely non-functional, though I've got the illumination of the gauges hooked up. I'm also adding some lighted pushbutton matrixes and a couple of 7-segment LED displays. Nothing needs to be accurate, I just want it to look somewhat convincing. Amongst the military surplus bits I've got hold of is the front panel of a Racal vehicle radio, which has two lovely HP HDSP-6508 16-segment LED modules, and I cannot resist trying to bring this to life. The LED modules are conveniently broken out into a pin header, for which I've established which pin corresponds to which segment - and they are common anode modules. I've only really used common cathode displays before, and it turns out finding a suitable driver for common anode displays is harder than I thoguht. There's the obsolete Philips SAA1065, which can still be bought as bare chips, but I don't have time to make a board for these. So I though I'd check here, if anyone has any suggestions? As I'm rather pressed for time I really need a plug'n'go type solution, or at least a finished breakout board - something likethe Adafruit HT16K33 "backpack", but for common anode displays.

author: Tomorokoshi
author_rank: Super Contributor
timestamp: February 24, 2019, 05:36:03 pm
content: Something like this in perf board wire-wrap sockets?https://www.digikey.com/products/en?keywords=MCP23017-E%2FSP-NDhttps://www.digikey.com/products/en?keywords=MCP23008-E%2FP-ND

author: Lomax
author_rank: Frequent Contributor
timestamp: February 25, 2019, 02:49:03 am
content: Scratch that, I'm an idiot - they are commoncathodeLEDs.Please distract yourselves from my stupidity with these pretty pictures!

author: Lomax
author_rank: Frequent Contributor
timestamp: March 06, 2019, 01:23:46 pm
content: Success, using the HT16K33 driver:Pin assignment:Code:HT16K33 Segment HDSP-6508-----------------------------A0 h 25A1 i 20A2 j 16A3 g2 18A4 k 9A5 l 5A6 m 8A7 g1 1A8 a2 19A9 a1 23A10 b 22A11 c 24A12 d2 4A13 d1 11A14 e 7A15 f 26-- dp 2
Driving 3 pin piezo buzzer? - Page 1
Forum section: electronics / projects

author: hal9001
author_rank: Regular Contributor
timestamp: August 07, 2024, 06:30:07 am
content: I found a 3 pin buzzer with labels F, M, G for pins. What do those letter mean? Can I drive it like a 2 pin buzzer with one pin to positive rail and another to a FET driving a square wave to ground? Will the RE46C100 drive it louder than just a FET?Cheers!

author: Zero999
author_rank: Super Contributor
timestamp: August 07, 2024, 08:40:46 am
content: Quote from: hal9001 on August 07, 2024, 06:30:07 amFeedback, Main and Ground.QuoteYes that will work, although it's piezo and therefore capacitive, so it will be louder when driven straight off the output off a microcontroller, assuming the voltage is equal. If you need to drive it at a higher voltage, with a transistor, then you need a resistor in parallel, to discharge the capacitance.QuoteYes, that IC will drive it louder because it has a push-pull output and drives it at the resonant frequency.

author: ArdWar
author_rank: Frequent Contributor
timestamp: August 07, 2024, 11:01:48 am
content: One simple and cheap way to drive piezo is to bridge it across two out of phase GPIO, or across inverting buffers if there's concern with uC max output current.3 terminal piezo buzzer adds an additional feedback pin that usually used to implement self resonant oscillator drive. Driving the piezo at its peak efficient frequency. It's optional, you can still drive it the "brute force" way ignoring the feedback pin.
Driving 48 LEDs from a single cell - Page 1
Forum section: electronics / projects

author: Jon86
author_rank: Frequent Contributor
timestamp: May 23, 2020, 03:43:20 pm
content: So my project involves driving 48 white LEDs in a grid pattern from a single 3.7V lipo cell.The LEDs will have about a 3V forward voltage at their rated current, so I'd like to avoid simply using a 48 channel linear driver with current sinks. I don't have much room for thermal losses here. Also routing 48 traces in a grid will be a bit of a nightmare, especially if I want to maintain good thermal transfer across the board.One option I'm looking at is the LED7707, 16 channels with a boost converter, so I can tie the LEDs together in series strings of 3 or 4, and let the IC boost the voltage up for me.This might be the optimal solution, but since I don't have much experience in the field I'm asking for some advice.Literally all I need is PWM dimming of the whole lot at once, and a relatively high efficiency (>85%?).If I can do it without SPI or I2C that'd make things simpler, but I'm sure that's where I'll end up.Anyone who's done something similar I'd love to hear your solution!Also, LEDs are rated for about 65mA, so I'm looking at around 10W for the whole lot.

author: coromonadalix
author_rank: Super Contributor
timestamp: May 23, 2020, 10:34:13 pm
content: With an buck boost converter you have to take in consideration the loss of your "autonomy" of your "single" cellIs it a led matrix display ?? you're a little vague, is it put on clothesFrom a single cell i found this unrealistic, what life expectancy you want ?Theres Charlieplexing i've read who could help ...

author: Jon86
author_rank: Frequent Contributor
timestamp: May 24, 2020, 03:53:16 pm
content: Not sure what you mean by autonomy?It's literally just 48 white LEDs, in a grid array. Not a matrix as such, I can wire them however I see fit.Multi/Charlie plexing might be an idea, but I'm keen to run them all constantly at their rated current and reducing flicker as much as possible.Not too fussed about run time, but I should be able to get roughly an hour from a 5000mAh cell if the efficiency of my driver is good.

author: SiliconWizard
author_rank: Super Contributor
timestamp: May 24, 2020, 04:54:33 pm
content: The LED7707 would be one of the simplest paths for this.It has a 4.5V min input voltage though, so a single-cell LiPo battery wouldn't do. You'd need a 2-cell battery, which, if you have an appropriate charger, would be a better solution in terms of efficiency (obviously) than putting an additional step-up converter in front of the LED7707.

author: Marco
author_rank: Super Contributor
timestamp: May 24, 2020, 08:11:40 pm
content: Quote from: Jon86 on May 23, 2020, 03:43:20 pmWhy not just make strings, use any old boost converter which can run off a single cell and then use a resistor to limit the current for every string? LED matching and thus current matching will not be ideal, but close enough. You can use a single MOSFET to PWM them all.
Driving a 0...90VDC 2A motor from 0-10V or 4...20mA or ... - Page 1
Forum section: electronics / projects

author: tchiwam
author_rank: Regular Contributor
timestamp: December 29, 2021, 09:55:51 pm
content: I am looking at a couple of drives from various manufacturer, is there any good SCR/SSR/drive to run a DC motor from 0 to 90VDC controlled by one of these : 4..20mA 0-10V 0-5VSomething that will not break my bank, used ebay or even new...

author: strawberry
author_rank: Super Contributor
timestamp: December 29, 2021, 11:42:32 pm
content: if DC brushed motor then cheapest option 500Hz PWM with LM555 and 150V ~5A MOSFET (google 555 motor controller circuit)could add overcurrent protectionif just turn on/off then SCR and opto zerocrosing SCR

author: jpanhalt
author_rank: Super Contributor
timestamp: December 30, 2021, 12:14:44 am
content: I have used KB Electronics drives for many years (https://www.kb-controls.com/). You can get open frame versions cheaper. Their DC drives will do what you want. I have one on my miniature lathe that I retrofitted with a DC motor. Works great with good speed control and at very slow speed. Ebay and some dealers often have cheap (e.g, ca. $100 new) offers for a small motor like you have.

author: tchiwam
author_rank: Regular Contributor
timestamp: December 31, 2021, 10:20:11 pm
content: KB it will be then. Something ready and go, for someone else. I don't want to have to support the circuit myself for too long.

author: jmelson
author_rank: Super Contributor
timestamp: December 31, 2021, 10:54:00 pm
content: Quote from: jpanhalt on December 30, 2021, 12:14:44 amYes, these are very good, and can run from 0-10 V command. But, WARNING, the signal inputs are NOT isolated from the mains! So, you need to provide whatever isolation is needed for whatever is going to control the speed. Easy if it will be a manual pot, not quite so easy if it will be a microcontroller.Jon

author: jpanhalt
author_rank: Super Contributor
timestamp: December 31, 2021, 11:53:39 pm
content: Here's the installation in the base of my Prazi 3" (?) lathe. Nothing could be easier or simpler. I can slow the Baldor DC motor to a walk for threading (no half nuts) or winding coils or springs.
Driving a 24V solenoid with a comparator under certain condition - Page 1
Forum section: electronics / projects

author: XaviPacheco
author_rank: Regular Contributor
timestamp: October 21, 2018, 10:44:54 pm
content: I'm getting from a Hall Effect magnetic sensor a variable voltage between 0.8 and 3V. When the voltage is less than 0.9V, I want to activate a solenoid valve. If the voltage goes more than 1V, the valve should be off. So I thought of an inverting comparator like shown below. For the voltage threshold, I will put a precision pot to carefully adjust it to let's say 0.9V. The valve is 24V/200mA. It works on the simulation. But do you think it could work well in real life? Would you make any improvement? I chose the 2N4401 BJT rated at 600mA, as my valve needs little current. Also, I'll use LM339.
Driving a cable from both ends? - Page 1
Forum section: electronics / projects

author: AntiMidas
author_rank: Newbie
timestamp: November 04, 2023, 04:37:19 pm
content: I am trying to drive a cable from both ends but my initial attempt has hit a snag. I want to drive 10khz bpsk from one end, and 1Mhz bpsk from the other. I have to AC couple to the cable as i also want to put a DC power supply onto it.My current design uses an op amp suitable for driving cables, but the feedback into the inverting input means that the op amps are fighting the incoming signal, resulting in a very distorted signal.Do i need to drive the cable through a filter so that the incoming signal cannot feed back into the inverting input?Is there a different way i could try driving the signals?Anyone got ideas how I could go about this or any ideas what to read up on?(attached is simplified drawing)

author: Someone
author_rank: Super Contributor
timestamp: November 04, 2023, 09:16:20 pm
content: A single capacitor works to separate 2 different frequencies (DC and kHz/MHz in your case), but you want to separate 3 things.Each source will want to present a low impedance within its "band", and a high impedance to the other "bands". That includes the DC source which was omitted from your drawing.Output impedance design is an exercise for the reader.

author: edavid
author_rank: Super Contributor
timestamp: November 04, 2023, 09:30:37 pm
content: The problem has nothing to do with your use of op amps.Rather than filtering the transmit signals, you can just add series resistors so the signals add linearly and do not distort. A bonus is that if you can somewhat match the nasty cable, you can reduce reflections.Then you can either implement some sort of hybrid at the receivers, or use bandpass filters there.ETA: Here's how it's done in telecom, but it seems like overkill for your situation:https://en.wikipedia.org/wiki/Telephone_hybrid

author: AntiMidas
author_rank: Newbie
timestamp: November 07, 2023, 09:09:27 am
content: Thanks. I read up on it and think i understand it a little better now. Adding the series resistor to the output did the trick. Thanks for pointing me in the right direction.
Driving a DC motor from a constant current sink - Page 1
Forum section: electronics / projects

author: OM222O
author_rank: Frequent Contributor
timestamp: June 02, 2020, 05:33:49 pm
content: For a robotics project I needed to design a "light house" where it spins a light 360 degrees. I ended up making a hexagonal shape with 3 pairs of LED COBs to cover all 6 sides. I then designed a current sink for driving the leds (basic op amp + N fet) and since they don't make op amps in 3 packs, I went with a quad design. That left one empty current sink which accidentally fits the current rating of the DC motor (it's a small geared one). I have tested it for a short while and it seemed to spin the motor without any problems.Are there any issues for long term use for either the sink circuit or the DC motor? I'm assuming the voltage across the motor goes all the way to VCC when changing poles because the op amp sees nothing for a while and that causes an initial current rush, since the inductance of the motor is quite low (again, small DC motor). Or maybe the back EMF from the motor can end up damaging the fets or the control circuit somehow? I'm just not sure if that's a good idea, but would be a very convenient one.

author: schmitt trigger
author_rank: Super Contributor
timestamp: June 02, 2020, 05:37:47 pm
content: You are talking about a brushed DC motor, correct?If so, there is always some overlap between the brush and the commutator segments, it never really goes open circuit.

author: OM222O
author_rank: Frequent Contributor
timestamp: June 02, 2020, 05:48:23 pm
content: yes it a 6V brushed geared DC motor rated for about 300mA

author: richard.cs
author_rank: Super Contributor
timestamp: June 02, 2020, 06:47:50 pm
content: You may find speed control is poor - when run from a current source the thing that's held constant is torque, so the speed then becomes heavily dependent on the load. In your case it sounds like you just want it to turn so it'll probably be fine. It is possible that the inductance of the motor might cause the current sink to go unstable and oscillate, but that shouldn't actually cause damage. You should probably have a diode across the motor to prevent damage to the fets if/when the control circuit decides to reduce the current rapidly.

author: ahbushnell
author_rank: Frequent Contributor
timestamp: June 02, 2020, 08:11:45 pm
content: You might want to put a freewheeling diode across the motor. This will prevent voltage spikes when you turn off the motor rapidly. 1n4007.
Driving a fet from a pic - gate resistor needed? - Page 1
Forum section: electronics / projects

author: JJalling
author_rank: Unknown
timestamp: October 26, 2013, 02:22:45 pm
content: Hi all,I'm designing a DCC decoder for a model train. My current motor driver design looks like this:http://jalling.net/~jonas/motordriver.pngBoth NPN transistors (Q4 and Q5) have an internal base resistor of 4K7 ohm, not shown in the schematic.I'm driving the H-bridge from a PIC18F14K22, as it has support for PWM-modulating a full-bridge.As space is a little tight I consider to omit the resistors between the pic and the gate on the two N-fets but is that a bad idea?What about the two capacitors C6 and C7? The plan was to use them as decoupling for the fets - should I just remove them?Thanks in advance.BR Jonas

author: stefandz
author_rank: Contributor
timestamp: October 26, 2013, 03:20:56 pm
content: This is a short answer, based on my experience (I'm off out so I have to be brief).Omitting the gate resistors shouldn't be a huge issue. You will get higher peak currents into / out of the gate capacitance, but the output impedance of the PIC will squelch some of this. I would try with and without and look at the VCC of the PIC - if it droops when driving the FET, put the resistors back. Otherwise likely fine. You will increase EMI doing this, but I doubt that is a problem for you.As for the 100nF decoupling caps, I doubt that omitting them will cause any problems for the motor. However, whatever noise the motor creates is more likely to couple back into anything sharing the same VCC. If space is an issue near the motors but less so elsewhere you could remove C6 & C7 and put extra decoupling at more sensitive stages on the same rail.All of that said, keeping the gate resistors and decoupling caps in is better, more robust overall design practice. Suck it and see I say - your scope is your friend in deciding if the design performs as you like or not.I imagine other people will have significantly different opinions to me on this - matters like this often generate strong emotional responses!

author: JJalling
author_rank: Unknown
timestamp: October 26, 2013, 04:51:20 pm
content: Thanks for your input,I'll follow your advise and try both with and without. I was initially going to skip the prototyping step, but I have just created a bigger pcb with room for experimenting.BR Jonas

author: Alana
author_rank: Frequent Contributor
timestamp: October 26, 2013, 05:21:54 pm
content: I'm playing with this topic too.I don't remember any big caps in factory made decoders connected anywhere near H bridge. There is just a 10uF/6V electrolytic for microcontroler power. I may check how its done in Lenz standard decoder on Monday evening when I'll be oiling my models.edit: pic of lenz standard dcc decoder - i see like 4 ceramics and one electrolitic, if you want something mesured/checked ask.
Driving a heater with a buck-boost converter: Component selection - Page 1
Forum section: electronics / projects

author: DanInvents
author_rank: Contributor
timestamp: April 12, 2024, 01:23:46 pm
content: Hi!I'm planning to use a buck-boost converter to control a heater (see attached files for application note and circuit diagram). The idea is to use a DAC converter to control the magnitude of the current and replace the LED that there is in the diagram with my heater.At this point, I have a few questions.What is the purpose of C3? Is it to provide a path for high-frequency signals?What kind of bandwidth requirements would there be on the op.amp?Thanks!

author: ajb
author_rank: Super Contributor
timestamp: April 12, 2024, 02:52:20 pm
content: Quote from: DanInvents on April 12, 2024, 01:23:46 pmBasically. You'll see that referred to as a "feed-forward" capacitor in some datasheets, and is often present in converters that use a simple resistor divider for feedback. It serves the same function as the capacitors that you often see in parallel with op-amp feedback resistors, essentially making the feedback more responsive to higher frequency changes in the output. When sized correctly, that stabilizes the system by suppressing higher frequencies that may otherwise result in oscillation.QuoteIt depends on the converter frequency. The op-amp circuit is in the feedback loop of the converter, so any lag it introduces becomes a phase shift in the converter's control loop, which will decrease the stability of the converter. This can be somewhat compensated for by C3, which effectively slows the converter's response to increase that phase margin at the expense of how responsive the overall loop is. Note that the effective bandwidth of an op-amp circuit depends on its gain, so larger gains require higher bandwidth op-amps.If you don't need to have one end of the heater connected to ground, you could theoretically remove the op-amp entirely. Instead, you'd swap the current sense resistor and the LED, and take the feedback from the point where the LED and sense resistor connect via a resistor. The DAC would connect to the feedback pin via a second resistor to adjust the current (See figure 4-1 in the appnote, and just replace Vref with the DAC output). The problem with that approach is that the voltage across the sense resistor needs to be around the feedback voltage on the converter which can result in significant power dissipation.

author: DanInvents
author_rank: Contributor
timestamp: April 15, 2024, 07:02:02 am
content: Thank you very much for your response, it has been very educational.
Driving a laser diode with a simple current mirror - Page 1
Forum section: electronics / projects

author: PythonGuython
author_rank: Contributor
timestamp: February 15, 2021, 03:31:12 am
content: I need to drive a laser diode whose optical intensity matches a square wave input up to around 3 kHz (It needs to switch on/off very quickly as I am trying to reproduce the rolling shutter effect). It turns out driving a laser is not trivial. Best practices say that I need to be mindful of transients, over-voltage, over-current, temperature, ESD, and more - all without getting laser in my eyes. Here's the thing, I just need to get this project working for a weekend. I don't care about maintaining a precise optical intensity, or running this for long periods of time. I need a quick and dirty solution.Let's say I need to run the LD at 125 mA, which creates a forward voltage of 6.9V. Someone tell me why I can't just put the laser diode in a current mirror if my MOSFET's are matched closely, given I manage to get my LD wired up without frying it with ESD.

author: twospoons
author_rank: Frequent Contributor
timestamp: February 15, 2021, 05:52:47 am
content: BJTs might be faster. And Vbe is ~0.7V vs ~1.5 VGth for the mosfet. Also if your matching isn't great adding small emitter or source resistors can improve matters a bit. Make sure your bjt's or mosfets are in close thermal contact, ideally in the same package, better still on the same die. Aim for the same dissipation in both devices - or the thermal transients will screw it up. Look at using a Wilson current mirror too (see attached). The power handling gets offloaded to the upper devices, letting the lower devices do the current mirroring with lower thermal loading, more constant collector voltages.I'd be inclined to power the LD off dc, and add a second current setting resistor off DC to set the idle current of the LD just below lasing threshold - unless the small amount of light that will result is going to be a problem for you.Other than that - go for it. The idea seems reasonable to me.
Driving a LED panel of size 64*22 (1408 SMD LEDs of 0603 size) - Page 1
Forum section: electronics / projects

author: DodZi
author_rank: Newbie
timestamp: August 25, 2018, 12:47:31 pm
content: Hi all!I believe myself to be in love with LEDs and recently decided to build a project with a LOT of LEDs. Hence a LED panel of 64*22 red LEDs.But soon I realized that to control these LEDs, multiple options lie before me. These would be :Breaking the panel into small parts and controlling each part with a separate controller. And then all these controllers will communicate with a host controller (Probably thinking of TI's TM4C123G for host uC and MSP430 28 pin for LED controlling part. Suggestions for this too?)Second is to use LED drivers, which I have never used and hence not able to choose as my first choice.Can anyone please let me know if I have missed any other option for driving these LEDs? Also which could be the best-suited method for the same?

author: Rerouter
author_rank: Super Contributor
timestamp: August 25, 2018, 01:14:08 pm
content: You have a nice byte aligned sized array, It will come down to your refresh rate a little, and if you need brightness control.LED driver IC's greatly reduce the amount of middle management you would otherwise have to do, e.g. writing the brightness values directly, but may blow out yur BOM price,If you do go the microcontroller path, Refresh rate and brightness dimming are the deciders, because going this road will likely result in shift registers, If you just need global brightness, this is easy as its just PWM'ing the output enable pin, If you want localised dimming, you will need to push out a new serial string for each PWM value, this has a limit based on how fast your micro can push this data out, deciding how many strings you break it into.You can cheat this a little if your micro has a wider I/O bit size, e.g. a 32 bit micro if it has all 32 lines exposed can update 32 shift registers data in 2 clock cycles, 1 to write the 32 bit word, 1 to pulse the data clock. However your micro will be burning time calculating the next PWM state, and reading in the next frame,
Driving a Mosfet with a compartor LM339 ... What I am doing wrong ??? - Page 1
Forum section: electronics / projects

author: Enea
author_rank: Contributor
timestamp: February 23, 2017, 01:50:21 pm
content: Hi folks,I would like to use a comparator LM339 to drive a power MOSFET.If the input voltage is above my threshold -> gate HIGH - mosfet ON - the motor runs - LEDON ON - LED OFF OFFIf input voltage is below the threshold -> gate LOW - mosfet OFF - the motor stops - LEDOFF ON - LEDON OFFLEDs are driven correctly.But Pin1 that drives the MOSFET is LOW and I am not able to drive the MOSFET. WHYYYYYYYWhat I am doing so wrongFor example, VIN = 11V ----> V2 = 9.6V (so the leds work just fine) BUT the pin for the gate has V1 = 0 !!Many thanks in advance for your help!!!Notes.Yes I am aware the mosfet I use is not a logic transistor who need 10V and proper temperature management ... but is ok in my application even if Vgs is in line with VCC <10V

author: Andy Watson
author_rank: Super Contributor
timestamp: February 23, 2017, 02:00:53 pm
content: The output of a LM339 is open-collector, it will only sink current. It needs an external source to pull-up the output.

author: mjs
author_rank: Regular Contributor
timestamp: February 23, 2017, 02:02:17 pm
content: LM339 like most comparators has an open collector output. Your LEDs work, because they're between VCC and OC output.Change the R8 to be between gate and VCC instead of gate and GND.

author: RoGeorge
author_rank: Super Contributor
timestamp: February 23, 2017, 02:02:43 pm
content: LM339 has open collector outputs, which means it can sink current coming from the V+, but it can not source (generate) current to V-.To generate a positive output voltage from LM339 (as needed to control a FET), you need to put a resistor between the LM339 output and V+.

author: Codebird
author_rank: Regular Contributor
timestamp: February 23, 2017, 02:37:22 pm
content: "If the input voltage is above my threshold -> gate HIGH - mosfet ON - the motor runs"... and immediately drops the supply voltage, causing it to turn off and your circuit to oscillate in weird and unpleasant manner.Getting the LM339 to switch a MOSFET is easy, but for your voltage-triggered-switch application you'll need a little hysteresis. Otherwise it'll be unstable.

author: Seekonk
author_rank: Super Contributor
timestamp: February 23, 2017, 02:44:22 pm
content: And I'd use that extra comparator to add a time delay. Any motor turning on will seriously drag down the voltage for a period of time. Don't forget the diode on the motor.

author: Richard Head
author_rank: Frequent Contributor
timestamp: February 23, 2017, 02:47:07 pm
content: Also, all the hash from the motor needs to be filtered with a decent sized electrolytic so it doesn't upset the comparator. Alternatively RC filter just the comparator supply.

author: Enea
author_rank: Contributor
timestamp: February 23, 2017, 05:49:00 pm
content: Hi folks,many thanks to everyone for all the answers. Now the circuit works !!!I appreciated also all the extra tips, and yes the diode was not in the schematic but was included in the project.Thanks all once more !!!
Driving a multi-mode laser diode - Page 1
Forum section: electronics / projects

author: Pack34
author_rank: Frequent Contributor
timestamp: October 12, 2016, 08:48:57 pm
content: I know the optical differences between a single mode and a multi-mode laser diode, but are there any differences in necessary driving circuitry?I've done multiple single-mode drivers in the past and I'm about to look at putting together a driver for a multi-mode and want to be sure I don't blow the thing up. I should be able to use the same driving circuitry, besides accounting for the additional current, correct?

author: grouchobyte
author_rank: Regular Contributor
timestamp: October 13, 2016, 02:33:20 am
content: Quote from: Pack34 on October 12, 2016, 08:48:57 pm@Pack34:There are no real gotchas and you are correct in your assumptions. However, you might consider that some laser structures like quantum-well and others can chirp depending on Di/Dt in pulsed operation. This chirp is limited with single mode, DBR or Bragg and FPerot lasers.With Multimode lasers ( also in pulsed operation) I have had issues with laser spectral lines hopping around randomly and affecting the spectral envelope, which in some applications, like test and measurement equipment, can cause lots of head scratching. If you are driving a MM laser CW then there are really no unforeseen surprises lurking.Probably unrelated is driving VSCELs. CW operation is tricky because the coherence length of the laser plays into laser noise performance as the beating of the laser light fed back into the cavity can play havoc on power, noise and spectral. An uncommon remedy is to modulate the current or thermally dither and then filter out the modulation at the receive end, This breaks up the coherence and keeps things stable. All lasers multimode and single mode have hidden gotchas, some significant and some negligibleLambda and power tempco should be considered, Use the Back-facet monitor PD in an APC loop if there is one in the laser package or a Peltier with thermal control for stable operation. Doing a compensation loop externally is fraught with problems so beware of doing it that way. As always, you should use appropriate precautions to prevent transients from zapping an expensive laser, avoiding design-engineer-angst and regret@LaserSteve, are you reading this?....anything I missed?@grouchobyte
Driving a parallel printer from switches! - Page 1
Forum section: electronics / projects

author: ChristofferB
author_rank: Frequent Contributor
timestamp: August 21, 2015, 12:56:22 am
content: Hey!In my quest to find use(full/less) peripherals for my ongoing 8-bit computer project, I thought about a parallel printer, but I'm not all sure on how the protocol works, so this might be more of a though experiment than something I want to do:I was wondering if it'd be possible to drive a centronics port parallel printer from switches alone- setting data with dipswitches, and strobe with a pushbutton?And of course also a button for line feed and maybe reset?I can't find any reference that this has been done (maybe because it's pretty useless, except as a demonstration).Thanks!--Christoffer

author: ChristofferB
author_rank: Frequent Contributor
timestamp: August 21, 2015, 01:13:03 am
content: fantastic! Thank you!-Christoffer
Driving a precision op amp directly from two batteries - Page 1
Forum section: electronics / projects

author: jeremy
author_rank: Super Contributor
timestamp: June 10, 2014, 10:56:30 am
content: Hi all,I need to make a very low noise amplifier with an opamp. I've selected the opamp: an OPA627 (because I found one lying around!). I only need +-5V swing on the output, and I was thinking of powering it straight off two 12V lead-acid batteries (I also have these lying around). Given that everything else in the circuit is just passives, will I run into any problems if the battery starts to slowly sag in voltage over time due to discharge? For example, if I was to use it as a unity gain buffer on a very good reference, would I notice any difference in the output?Just to be clear, I do not intend to use any regulation, just decoupling.Thanks in advance for your opinions.

author: Rerouter
author_rank: Super Contributor
timestamp: June 10, 2014, 11:15:51 am
content: a schematic would best show if any parts of the circuit are supply voltage dependant,in general a unity gain buffer should not be effected by uneven or slowly diminishing supply voltages until they drop below the minimum or inside the signal range,

author: jeremy
author_rank: Super Contributor
timestamp: June 10, 2014, 11:22:10 am
content: Hi Rerouter,Thanks. Here is a schematic, but I'm not sure how useful it will beGain will be less than 10.

author: Rerouter
author_rank: Super Contributor
timestamp: June 10, 2014, 08:57:07 pm
content: you will have to tie your ground point to something in reference to the input or/and output signal to make sure it doesnt shift, but yes that should work,

author: dannyf
author_rank: Super Contributor
timestamp: June 10, 2014, 09:17:39 pm
content: QuoteYes, eventually.QuoteSooner for that circuit than an unity follower.
Driving a single mosfet - Page 1
Forum section: electronics / projects

author: auto_mitch
author_rank: Newbie
timestamp: March 30, 2013, 05:07:22 pm
content: Hi!I am trying to build a high power speed controller for a DC motor.I want to control the motor only to one direction. I decide to use a single mosfet with a mosfet driver as the following schematic shows.Mosfet:http://www.irf.com/product-info/datasheets/data/auirl1404z.pdfDriver:http://ww1.microchip.com/downloads/en/devicedoc/21422d.pdfD1:http://www.sirectifier.com/datasheet/High%20Tjm%20LOW%20IRRM%20Schottky%20Barrier%20Diodes/MBR3050CT%20thru%203060CT.pdfThe frequency of the pwm is 23,53Khz. The problem that i face is that the mosfet is getting very hot when i try to change the duty cycle of the pwm. I have tried lower freq like 5Khz but the mosfet is getting hot again.I dont know if there is something wrong with my driver. Any ideas?

author: NiHaoMike
author_rank: Super Contributor
timestamp: March 30, 2013, 05:10:09 pm
content: You need another fast recovery diode across the load.
Driving a speaker with CODEC analog output - Page 1
Forum section: electronics / projects

author: zphaze
author_rank: Contributor
timestamp: June 17, 2020, 05:41:11 pm
content: Hi,I'm using a SOM (System on module using NXP iMX8M) that has an option to use a WM8904 codec.The thing is that, on the SOM, I can't access LINEOUT, only HPLOUT and HPROUT (output amp).I want to drive a speaker with an OK quality mono signal, so I will use a summing opamp and then output the signal inside a LM4862.Speaker I'd like to use :https://www.digikey.ca/en/products/detail/cui-devices/CDS-15158-SMT-TR/5355550Now, according to the datasheet, the WM8904 has a built-in "Wolfson class W headphone amplifier". The datasheet is confusing.Never heard of a class W amp. What I'd like to know is what kind of output should I expect from this amplifier?The WM8904 seems to be powered by a 1.8V smps. But I wonder if it's DC-biased or not? The datasheet seems tosay the headphone output is ground referenced, does that mean it goes from something like 1.8V to -1.8V?I wonder if anyone more familiar with this kind of IC could help out! Thanks! It's only really to power a small speaker.

author: TheMG
author_rank: Frequent Contributor
timestamp: June 17, 2020, 06:36:14 pm
content: Class W is a meaningless marketing term, not an actual amplifier class.From their description of it, sounds like it's a class G or H, essentially a traditional class AB output but with dynamically variable supply voltages to limit power dissipation.

author: zphaze
author_rank: Contributor
timestamp: June 17, 2020, 06:54:57 pm
content: I see. Marketing huh.Still, if it's class AB that would mean there is no actual DC offset?

author: Marco
author_rank: Super Contributor
timestamp: June 17, 2020, 08:31:14 pm
content: The block diagram shows the signal outs and ground directly connected to a jack, so yeah presumably it needs no dc blocking capacitors.PS. oh the datasheet explicitly says it doesn't need capacitors.
Driving a white LED with a single Gold Cap 2.7V 22F - Page 1
Forum section: electronics / projects

author: Didix
author_rank: Regular Contributor
timestamp: February 17, 2015, 07:35:45 pm
content: Any ideas how I could do this?-Didix

author: Mr. OBrien
author_rank: Contributor
timestamp: February 17, 2015, 07:46:42 pm
content: A quick google and I believe this circuit will do what you need with very little tweaking.http://cappels.org/dproj/ledpage/leddrv.htm

author: Phaedrus
author_rank: Frequent Contributor
timestamp: February 17, 2015, 07:50:38 pm
content: What context is this in? Is this cap being used to keep some kind of indicator light on after the supply voltage has been removed? Is there a reason you're using this specific cap? What's the Vfd and If of your LED? What level of brightness do you need? What kind ofbatterycap life are you aiming for?If you just need to boost voltage to power some LEDs from a low voltage source, something like a Joule Thief would work, or even that "free energy" circuit Dave debunked a while back:

author: Didix
author_rank: Regular Contributor
timestamp: February 17, 2015, 08:00:25 pm
content: Well, I never have used a Gold Cap before and I just wanted to have oneNow I am looking for some test applications.I have a flashlight with a white LED and a Gold Cap. The Gold Cap is charged by shaking the lamp (a neodym magnet and a coil that act as a generator).That was acually inspiring me for my first trial.I will follow up on your hints! Thanx a lot-Didix

author: compet17
author_rank: Regular Contributor
timestamp: February 22, 2015, 11:50:55 am
content: Just Google for "joule thief". You will find many simple schematics. And if it works with a 1.5Vbattery, it will also work with a 2.5V cap. Some of the circuits go down to a supply voltage of 0.5V

author: mariush
author_rank: Super Contributor
timestamp: February 22, 2015, 12:33:07 pm
content: Buy a proper boost led driver, that will work on a wide range of input voltages.For example this one will work from 0.8v to 8v so it would pull out a lot of energy from the capacitor before crapping out :http://uk.farnell.com/diodes-inc/zxsc310e5/ic-led-driver-boost-converter/dp/1226478It would also allow you to control the amount of current going into the led, so you could add for example a "feature" like low / med / high brightness slider.See page 8 of datasheet, only need an inductor and a transistor and a resistor (to control current) to make it work.

author: Didix
author_rank: Regular Contributor
timestamp: February 22, 2015, 07:07:49 pm
content: I am already collecting toroid cores-Didix