hybridfree/eevblog-posts huggingface dataset:
Simple Relay Question's - Page 1
Forum section: electronics / beginners

author: iampoor
author_rank: Frequent Contributor
timestamp: November 13, 2013, 04:14:02 am
content: Hiya!I have never used relays before for anything beyond basic SPST on/off control. So naturally I have a few questions (some of which I am embarrassed to ask! haha)This is an excerpt from the NEC EA2 datasheet. I want to make sure I have this right. When the coil is not energized, 2/3 are connected, and 3/4 are not. When the coil is active 3/4 are closed, and 2/3 are now open (Mirrior for the bottom side too). Is this correct?Also, when placing relays near small signal electronic devices, is there any particular standard way to minimize interference through layout? I was thinking of shielding all of the relays and then routing the PCB tracks to the sensitive components.Thanks!

author: Reboot
author_rank: Contributor
timestamp: November 13, 2013, 04:21:38 am
content: Yes the relays are shown in the non energized condition. (it says that right on your picture)Put a separate ground plane around the coil connections on the pcb and keep it away from the sensitive traces. You would only get interference when the relay is being energized or de-energized.

author: iampoor
author_rank: Frequent Contributor
timestamp: November 22, 2013, 07:54:26 am
content: Quote from: Reboot on November 13, 2013, 04:21:38 amOops, I missed that! Thanks for not beating me into the ground for being a dummy! O0Could a bypass capacitor be used to shunt any voltage spikes from the relay being energized/denergized? Id like to minimize noise as much as possible.

author: christopher iles
author_rank: Regular Contributor
timestamp: December 22, 2013, 05:12:49 am
content: Always place a diode in parallel with the relay coil to prevent the back EMF.

author: WIRENUT
author_rank: Contributor
timestamp: December 27, 2013, 01:06:12 am
content: This is a really cool circuit simulator. It takes some time to figure out how to use it, but they have very common circuit configurations already built for you, you can "see" how the current flows, slow it down and speed up simulations. You can even monitor the signals with a virtual scope too.There is one that shows you how back EMF voltage happens and how to get rid of it.Check it outhttp://www.falstad.com/circuit/you may have to download the java plug-inany questions shoot me a message

author: digsys
author_rank: Unknown
timestamp: December 27, 2013, 01:17:46 am
content: Normally they mark them C(COM) NO(N/O) and NC(N/C)To reduce noise - Use a lower power coil (ie higher resistance). You can often find lower power versions of most relay types.Otherwise a snubber diode and a RF cap across the coil AND one trick I often use is a series resistor with the coil.Even if it's only 1/10 coil resistance, it makes a big difference. To find the "perfect" value, try various values until the relay failsto energise, then 1/2 that value. You'll find most 12V Relay (eg) will operate down to 8V ish and hold on to 4V ish.
Simple reversing motor w timer for Halloween - Page 1
Forum section: electronics / beginners

author: Eighthave
author_rank: Newbie
timestamp: October 01, 2025, 09:08:24 pm
content: Hello,I am trying to create a moving decoration for my front window. It is a doom buggy decoration from The Haunted Mansion at Disneyland. I have a frame for it to be mounted on that has rails so it can slide smoothly. I used ChatGPT to get me to where I am now with the electrical stuff, but as is sometimes the case, the details get a little fuzzy.What I want to do is simply have a DC motor run one way for X amount of time to travel down the rails, then reverse and travel back for that same amount of time and then just repeat. I have a timing belt pulley system under the rails. I have a 12 volt power supply, a drok timer relay, an omron MY2N DC12 DPDT general purpose relay and a 12V 25 rpm DC motor. I have gotten to the point where the timer works as I expect it to, but I can only get the system to go in one direction. I can also get the DPDT relay to activate, but haven’t figured out how to integrate it so it is useful, everything I’ve tried has produced nothing more than the timer by itself does. So, I need help reversing the polarity using a timer. I feel like I’m close, but that’s not quite enough here.Thanks for any help, I haven’t worked with electrical stuff in many years, and even then it was only the simplest things in high school.Dave

author: themadhippy
author_rank: Super Contributor
timestamp: October 01, 2025, 09:52:51 pm
content: timer relay switches the coil of the omron relay and the contacts on the relay reverse the polarity of the supply going to the motor,sumfing likeshttps://tinyurl.com/22smdywl,the 2 leds are just to show its changing polarity
Simple source transformation question - Page 1
Forum section: electronics / beginners

author: renzoms
author_rank: Regular Contributor
timestamp: October 12, 2020, 11:57:59 pm
content: I know I can compute source transformations using the method shown here in the blue index card herehttps://imgur.com/a/RXwJT3r.I used both of these methods, in an exercise herehttps://imgur.com/a/LHiRIjLMy solution is herehttps://imgur.com/a/0AuJNJ3Now, I have some questions about this sample circuit herehttps://imgur.com/a/rO5HozNI know if I remove Va, R1, and R3 from the circuit, I can source transform Is and R4.If I remove R3 from the circuit, can I source transform Is and R4? I understand that the possible answers are "No, Va and R1 affect the circuit... don't allow this...", and "Yes, Va and R1 are both strictly parallel to Is and R4 so you can source transform."
Simple Speaker Selector - Page 1
Forum section: electronics / beginners

author: Darlington
author_rank: Contributor
timestamp: January 12, 2025, 06:42:32 pm
content: Hello community,I am trying to design a simple spekaer selector for 100V line speakers.I will leave you part of the circuit here.I have a serious doubt regarding any clicks or pops that might occur at the during switching to one of the 4 zones provided.I assume that the length of the cables could affect this even more as the parasitic capacitances could increase the problem.What are your thoughts on this? Could anyone recommend any modifications that could be made?

author: m k
author_rank: Super Contributor
timestamp: January 24, 2025, 05:52:26 pm
content: You need a snubber that disconnects later.Maybe two relays per channel is needed.

author: JustMeHere
author_rank: Frequent Contributor
timestamp: January 24, 2025, 08:06:06 pm
content: You need to account for amps that do not have a common ground. It looks like you're only switching one speaker wire.Also, in amps that do have a common ground, you want to keep your wires next to each other to prevent noise from cross-talk and ground loops.
Simple Sweep Generator - Page 1
Forum section: electronics / beginners

author: Unknown
author_rank: Unknown
timestamp: June 26, 2013, 02:36:44 pm
content: Hi everyone, I have a need for a sweep generator , but would like to build my own if possible one up to 5/10 Mhz, do any of you have any idea's please.Paul

author: Paul Price
author_rank: Super Contributor
timestamp: June 26, 2013, 03:22:31 pm
content: Paul,What kind of output...sinewave I assume

author: Unknown
author_rank: Unknown
timestamp: June 26, 2013, 03:34:21 pm
content: Hi Yes if possible, I have a function generator and one of the inputs states "sweep input", so I wonder if that means sweep generator input or I wonder if it means a Sweep oscillator input, then use the function generators range, either way I don't mind , I'm just at a loss how to go about building one.Paul

author: WBB
author_rank: Regular Contributor
timestamp: June 26, 2013, 05:38:11 pm
content: My guess is it's a VCF (Voltage Controlled Frequency) input. The voltage presented to that input determines the frequency. You would feed a ramp signal into that input and the frequency will follow the voltage of the ramp signal.

author: Unknown
author_rank: Unknown
timestamp: June 26, 2013, 06:41:06 pm
content: Yes I've done it, function generator on sine wave 20 kHz then I fed a 6 kHz from my signal generator into the sweep input of the generator, and its sweeping brilliant . Thanks WBB for making me use the grey matter
Simple voltage divider - Page 1
Forum section: electronics / beginners

author: cog
author_rank: Newbie
timestamp: March 24, 2015, 08:03:29 am
content: Hi,This is my first post-- I've watched the blog on Youtube for a while.I'm trying to build a simple voltage divider circuit from a schematic. I've built-traced-rebuilt this thing a half dozen times now, and yet each time I get the same result. Turning the pot gives me an output from 9V to 12V, with very little variation in between. At about ~50-ohm on the pot it just rapidly starts going up or down.It is supposed to give an output of 1.25V to 10.50V. I've tested each of the components, they all seem OK. Here are the values for the resistors and capacitors:C1, C2 - 100uF 25V (booklet specified 20V, but I assume 25V is OK?)R1, R2 - 10K-ohm 0.5W resistorsR3 - 1K-ohm 0.5W resistorR4 - 10K-ohm pot (linear)R5, R6 - 100-ohm 0.5W resistorsAnyone have any troubleshooting tips for this?Attached is a scan that shows the schematic, and a current picture of my breadboard. The red/black wires on the bottom are where I'm measuring my output voltage from.This particular schematic is from a small booklet included with a Joe Knows Electronics kit. Any help would be appreciated, thanks!Joe

author: daddylonglegs
author_rank: Contributor
timestamp: March 24, 2015, 10:14:10 am
content: The MJE172 seems to be a PNP transistor, see:http://www.onsemi.com/PowerSolutions/product.do?id=MJE172However the schematic has this drawn and used as an NPN transistor.The behaviour you describe is consistent with having a PNP in the Q2 position. The feedback through Q3 and Q1 acts as positive feedback rather than the intended negative feedback. As a result, over most of the pot adjustment range the pass transistor (Q2) is held fully on and over part of the adjustment the output is unstable.You could place an NPN transitor in Q2. It would be up to you to test for stability and regulation over the full range of output voltages and currents. Alternatively you could look for a known good circuit from a different source.

author: mikerj
author_rank: Super Contributor
timestamp: March 24, 2015, 12:26:10 pm
content: Quote from: daddylonglegs on March 24, 2015, 10:14:10 amThat's very odd, if you get anMJE172 from STit's a NPN

author: Marco
author_rank: Super Contributor
timestamp: March 24, 2015, 12:55:16 pm
content: It does seem you are using a PNP while it needs a NPN.BTW, the way that book draws the circuit is silly and needlessly confusing and using a 100uF capacitor (C1) just to get the regulator stable is wasteful ...

author: cog
author_rank: Newbie
timestamp: March 25, 2015, 05:21:09 am
content: Thanks for the feedback, it was the MJE172 transistor. I replaced that with the NPN equivalent (MJE182) and it worked!Frustrating that the first circuit in a booklet titled "How Circuits Work" contains such an error. Oh well, it gives me something to look at and learn from.Also, if using C1 to stabilize the voltage is wasteful, what would a better alternative be (without completely changing the circuit)??Thanks,Joe
Simple voltage range regulator 2V-4V - Page 1
Forum section: electronics / beginners

author: Sebzy
author_rank: Contributor
timestamp: February 25, 2019, 11:50:45 pm
content: Looking for some advice on best way to build a DC simple voltage regulator for circuit bending musical instruments. here's the requirementsinput : 5-12V @ 1A DCOutput : 2V-4V @ 500mA DCFrom a quick search it looks like an LM317 is a possible solution.

author: bson
author_rank: Unknown
timestamp: February 26, 2019, 12:31:40 am
content: Well, if you feed it 12V in and 2V out, at 500mA you'll be dissipating 5W. It'll get pretty hot.

author: jeroen79
author_rank: Frequent Contributor
timestamp: February 26, 2019, 12:47:15 am
content: And the LM317 may not be able to output 4V from 5V in at 500mA.A low dropout regulator may be more suitable in that case.But that will still have the issue of dissipation.You could also use a switching regulator.These come as drop down (buck) and also up/down (buck/boost).These are much more efficient.

author: Dmeads
author_rank: Regular Contributor
timestamp: February 26, 2019, 08:04:03 pm
content: MY electronics teacher has some amazing videos on linear shunt and series regulators that could absolutely help you out. Please check out that playlist.also RSD academy on youtube has some great videos on precision voltage regulators.Watch this part 4:and part 5 goes over current limiting which should help you out with the 500mA current limit.I have a good bit of experience with these regulators, and I'm designing some more right now. You can email me if ya want dominic.meads@oit.edu or we can just talk on the forum.the problem with the LM317 is that it is not very efficent and acts kind like a resistor. It just wastes a bunch of power as heat.

author: jeroen79
author_rank: Frequent Contributor
timestamp: February 27, 2019, 12:55:14 am
content: Quote from: Dmeads on February 26, 2019, 08:04:03 pmThis is a problem with all linear regulators, not just the LM317.Shunt regulators can be worse as the shunt will draw additional current through the dropping resistor and itself, resulting in even more power lost as heat.
Simple way to charge battery from capacitor? - Page 1
Forum section: electronics / beginners

author: THATguy
author_rank: Regular Contributor
timestamp: January 07, 2018, 07:06:47 pm
content: I have a charged capacitor.Does my circuit charge the battery?(I might need to reverse that battery's polarity :p )I've seen someone use an AC-DC transformer and bridge rectifier, but was hoping there was a simpler way.(this is my second atempt, my previous post was not clear)
Simple way to connect composite video output to 2 monitors? - Page 1
Forum section: electronics / beginners

author: Logan
author_rank: Frequent Contributor
timestamp: May 22, 2022, 12:26:41 pm
content: Hi.I need to connect an NTSC video source to 2 monitors at the same time. I tried just connect them in parallel, but the video become darker. I think it's because the equivalent impedance become too low. Is there any way to solve it without a complex and huge dedicated video splitter? I'm thinking if I can modify one of the monitor to infinite impedance(they call that high-z?). But I don't know how to find the input signal terminator. Any ideas?Thanks.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: May 22, 2022, 02:59:07 pm
content: Bandwidth of composite video is quite low, so you could quite easily make a video splitter / buffer from two opamps.Or just crank up the brightness knob on your monitors a bit.

author: jmelson
author_rank: Super Contributor
timestamp: May 22, 2022, 03:40:22 pm
content: Most "industrial video" monitors have a Hi-impedance / 75 Ohm switch. Send the video to the first monitor, set to Hi-Z, then use a BNC tee to send to 2nd monitor, set switch to 75 Ohm. This only terminates the cable at the second monitor.Jon

author: edavid
author_rank: Super Contributor
timestamp: May 22, 2022, 04:24:15 pm
content: If the monitor does not have a termination switch, it's usually easy to find the 75 ohm termination resistor near the input connector. Sometimes there are 2 150 ohm resistors instead.Otherwise, simple distribution amps are very cheap:https://www.amazon.com/Powered-Splitter-Composite-Distribution-Amplifier/dp/B082XTKN7Lhttps://www.bhphotovideo.com/c/product/892526-REG/ocean_matrix_def_1x2da_1_x_2_composite.html

author: Logan
author_rank: Frequent Contributor
timestamp: May 23, 2022, 02:32:00 pm
content: Thank you everyone!
Simple way to test capacitors? - Page 1
Forum section: electronics / beginners

author: L0max
author_rank: Contributor
timestamp: June 09, 2020, 06:35:35 am
content: Hi,What is the best way to test capacitors that have been removed from a circuit? Is there a reasonably priced device I can use to perform the test?Thanks,'max

author: connectTek
author_rank: Regular Contributor
timestamp: June 09, 2020, 07:54:48 am
content: https://www.ebay.com.au/itm/LCR-T4-Mega328-Transistor-Tester-Diode-Triode-Capacitance-ESR-Meter-W-Shell-HoP/303579449983?_trkparms=ispr%3D1&hash=item46aebeca7f:g:JjEAAOSwtVdezcnp

author: ercapoccia
author_rank: Regular Contributor
timestamp: June 09, 2020, 07:55:17 am
content: You can use an LCR meter to measure ESR, capacitance and other characteristics of the capacitor.For around 20$ you can buy a Component Tester and for 100$ a decent LCR meter (Der EE DE-5000)
Simple wireless switch using BTE/ANT+? - Page 1
Forum section: electronics / beginners

author: Pink Possum
author_rank: Newbie
timestamp: July 03, 2013, 10:04:56 am
content: Hi all,I'd like to get your expert opinions on the following:I'm trying to build a simple device. In one circuit, a switch closes. This sends a signal wirelessly to a nearby circuit (~1m away), which receives the signal and turns on an LED. When the first circuit breaks, the LED turns off. Sounds simple.The circuit containing the switch has to be very small/lightweight, and power conservative. I'd like to have more than one of these switches around and by closing either switch the LED would turn on. But these switches must be paired with the LED, so that another separate LED nearby will not be turned on.This led me to think about using something like Bluetooth Low Energy or ANT+, because the modules are really small and can be powered by a button cell battery for months. I can't use IR because there's no direct line of sight.Are there any alternatives besides these two options?If I choose BTE, what do I need apart from the module to get the circuit working? I mean stuff like PC-module connection, battery connection or IC or other stuff like controllers?Thanks

author: Codemonkey
author_rank: Regular Contributor
timestamp: July 03, 2013, 10:24:35 am
content: Look at 802.15.4. Plenty of higher level protocols sitting on top of that, ZigBee for example, or if you want something a bit less overkill then some of the Silicon vendors own stacks (NXP has JenNet, Someone from Atmel posted a link to theirs on here a few days ago).You could just use the 802.15.4 MAC layer messages yourself rather than bother with all the extra overhead of a tree/mesh stack if all you're doing is simple point to point/point to multipoint messaging (no routing from one node to another).

author: cthree
author_rank: Frequent Contributor
timestamp: July 04, 2013, 03:10:48 am
content: Xbee is an option which is basically 802.11.4 mesh networking, but...If you just want to replace a cable with a pair of radios then there isn't much easier a way than to use a pair of RovingNetworks RN42 modules.http://rovingnetworks.com/resources/download/65/Bluetooth_Cable_replacementhttp://rovingnetworks.com/products/RN4226uA in standby.
Simplest circuit 5v to on switch - Page 1
Forum section: electronics / beginners

author: marce002
author_rank: Regular Contributor
timestamp: July 08, 2024, 02:38:48 pm
content: HiCan you help me with the simplest circuit you can think of to do a "timed on" switch when 5vol.is present and keep on for 2 seconds.. i need that an old android phone (connected to 5v when car ignition is on) can turn on by wiring cables to the power on button.... need 2 seconds to be switch on or closed to make it turn on when 12v to 5v is present.... to turn off simply disconnect power... just need the turning on part. i have Res caps mosfets arround and the complex task to solder wires in the s4 i9500 (phone no battery just 5v attached + diode and redistor) power on button....if you have another idea welcome....SUMMARY:i just want to turn on my old s4 from off with a very fast booting ROM and my custom APP autoexecuted (all working that part) AS SOON AS car ignition is on.. phone is now directly to 5v

author: xvr
author_rank: Frequent Contributor
timestamp: July 08, 2024, 07:31:02 pm
content: NE555 in monostable cuircuit + reed ralay

author: Andy Chee
author_rank: Super Contributor
timestamp: July 08, 2024, 08:39:08 pm
content: 12F675 PIC or ATtiny microcontroller
Simplest Rectifier for LEDs - Page 1
Forum section: electronics / beginners

author: wheemzy82
author_rank: Newbie
timestamp: October 22, 2019, 07:20:11 am
content: Hello,I have a 1600v bridge rectifier module.I have LED strip lights.The original power cord for the LED strip (which I lost) is 100-240 AC to 125vdc output @8A with a built in 8A fuse max.Any foreseeable problem with using this module given that the module is rated for much higher power?The only reason I am reluctant is because I haven't quite grasped when a power supply is active (which would destroy the leds?) vs passive (which is presumably ok).Thanks,Matt

author: Zero999
author_rank: Super Contributor
timestamp: October 22, 2019, 07:45:55 am
content: The two are most likely not interchangeable.A 100 to 240VAC to 125VDC module will be a switched mode power supply, which will regulate the output voltage at 125VDC, even if the input voltage changes.A bridge rectifier is just that, a simple bridge rectifier, with no smoothing or voltage regulation.
Simplest Remote Controlled Latching LED - Page 1
Forum section: electronics / beginners

author: Kedar264
author_rank: Regular Contributor
timestamp: February 11, 2015, 07:37:00 am
content: here i made simplest remote controlled latching led see the videoi installed led in front of photodiode and conected led in seris with photodiode ,this forms receiver circuitfor remote circuit , i used infrared led with some ressistor and push button.simple circuit but works awesome in dark or meduim light condition,but when placed in very high lihgt conditions enviormental light triggers and latches the circuit. to turn off led jus block light between led and photodiode.
Simplest Soft Latching Power Switch for relay - Page 1
Forum section: electronics / beginners

author: indnut
author_rank: Newbie
timestamp: January 21, 2015, 01:48:23 pm
content: I was wondering if the soft latch circuit featured in the EEVblog #262 - World_s Simplest Soft Latching Power Switch, video can beused to energize and de-energize a relay coil? Latching and unlatching the relay.

author: gregallenwarner
author_rank: Regular Contributor
timestamp: January 21, 2015, 03:32:32 pm
content: I don't see why not. Just make sure you stick a flyback diode across the relay's coil so you don't damage the MOSFET.

author: retrolefty
author_rank: Super Contributor
timestamp: January 21, 2015, 06:25:41 pm
content: If you are going to use a relay anyway, why not just use a latching relay to start with? They come in single and dual winding styles and are available in the same DIP size packages as other mini-relays.

author: indnut
author_rank: Newbie
timestamp: January 21, 2015, 07:47:08 pm
content: I am going to us 32 for a model RR project and I have over 200 relays but none are latching. Trying to use some of the stuff on hand. Running out of storage room and hard to organize all the stuff I have collected. Just started working in electronics after I retired and it has turned me into a hoarder I think. I have cases and cases of components and every time I go to try somethingI have to order more stuff and 50 or 100 pieces are cheap so...... Being new I am sure what I have would sometimes work finebut lack of knowledge is my handicap. :-)
Simplest up-to-date way to detect USB possible intensity ? - Page 1
Forum section: electronics / beginners

author: Jaunedeau
author_rank: Regular Contributor
timestamp: April 10, 2016, 05:21:39 pm
content: Hi,I am making a lamp with leds. The lamp will have an MCU to do useless animation. In normal conditon, the lamp will draw 1 to 2 amps. Of course when I plug it to a computer for firmware update (or for any other reason), I want to be sure to only draw 500mA after I have politely asked permission to do so.I've spent hours reading the USB and USB-IF documentation, and learned many things, but still don't want to spend more time prototyping and debugging the code myself (that would take as much time as the rest of the project !).So my question is : What is the simplest IC I can buy that will tell me how much current I can use (and would possibly be able to deal with non standard Apple chargers) ?For now, microchip's USB3751 seems rather ok (0.5mm pitch, no bga, easy to source since I will order things from microchip, only require 1 external capacitor). The thing is that it does not know about apple chargers, and don't tell you exactly how much current you can draw (e.g. it will tell you "Dedicated charging port", but this could be from 500mA to 2.5A available).What is you current solution to this problem ?Thanks you,John.

author: Kilrah
author_rank: Unknown
timestamp: April 10, 2016, 05:32:48 pm
content: There can be no such thing since there is no standard beyond 500mA (not counting the newest stuff that isn't really in use yet) and everybody does a bit what they want.Devices often kinda self-regulate either actively or just naturally with the voltage drop of poor PSUs that get overloaded.You should probably start low, try a few things and allow yourself more current at each step, e.g.No enumeration, 100mA maxIf enumeration, negotiate up to 500mA, draw what you're allowedIf USB lines shorted you get a "charging port" that can support anything between 500mA and 2A but you have no way to know how much.

author: rstofer
author_rank: Super Contributor
timestamp: April 10, 2016, 07:29:37 pm
content: Basically, the D+ and D- pins will exhibit an impedance to ground of 15k ohms if the device is connected to a PC and the pins are left open for a charger. Here is an article/datasheet that discusses the problem in detail:http://www.skyworksinc.com/uploads/documents/Automatic_USB_Detection_AppNote_202742Apdf.pdfYou are trying to detect a charger (in effect) so I searched for 'usb how to detect charger'. There are a number of links.You let the uC detect whether it is powered by a charger or a USB port and if it is a charger, gate a MOSFET to pass the 5V to the loads.Maybe this will help:http://www.ti.com/lit/ds/symlink/bq24392.pdf
Simplifying transfer function - Page 1
Forum section: electronics / beginners

author: promach
author_rank: Frequent Contributor
timestamp: October 18, 2020, 10:08:57 am
content: How to obtain the expression on therighthand side of thesecondequal signin the first line ?Same question for the second line.

author: ledtester
author_rank: Super Contributor
timestamp: October 18, 2020, 07:50:03 pm
content: Just note that:$$\frac{B}{A+B} = \frac{AB}{A(A+B)} = \frac{A\parallel B}{A}$$
Simulate button press with passive components? - Page 1
Forum section: electronics / beginners

author: eevfan007
author_rank: Contributor
timestamp: January 27, 2014, 09:23:08 am
content: Hi!In my work with hacking a treadmill, I have soldered leads onto the buttons on the treadmill. By shorting the leads, the button is pressed, obviously.When I control this through an arduino I use a 5v relay. But the "clicking-sound" from the relay annoys me, and I was thinking that the same must be possible through the use of transistors. Are there any added risk of connecting the leads between the collector and emitter, and just sending a small amount of current into the base of the transistor to have it "open/push the button".Or would an opto-isolator work just as well maybe ?

author: Rerouter
author_rank: Super Contributor
timestamp: January 27, 2014, 09:38:58 am
content: it depends on what its driving, an optocoupler would be better

author: Psi
author_rank: Super Contributor
timestamp: January 27, 2014, 09:45:20 am
content: A reed-relay could be a good drop-in replacement and would work exactly the same as the existing relay except the noise would be so small i doubt you'd hear it.Reed relays can't handle much current but the treadmill buttons are likely low current inputs to the treadmill mcu.(i'd check that though)

author: SeanB
author_rank: Super Contributor
timestamp: January 27, 2014, 06:46:04 pm
content: I had a lot of success using a CD4066 quad analogue switch. There is a video on the EEVBLOG channel about interfacing them as well.

author: cwalex
author_rank: Frequent Contributor
timestamp: January 28, 2014, 01:29:24 am
content: Quote from: eevfan007 on January 27, 2014, 09:23:08 amThe most common button connection in electronics that I have come accross is a pullup resistor and the button pulls down to gnd. You could try just connecting one of the arduino digital pins to the treadmill where the button would connect and just set to low when you want to simulate button press.

author: ivaylo
author_rank: Frequent Contributor
timestamp: January 28, 2014, 08:59:51 am
content: Trying to make sense of the title here. Do you mean "passive" like a transistor, vs. "active" like a relay? Because none of the options you ask for involve passive elements, if you know what I mean...

author: ivan747
author_rank: Super Contributor
timestamp: January 28, 2014, 03:47:28 pm
content: I think he meant discrete components. I'd go for the optocouplers or the reed relays. Remember to connect the optocoupler's transistor the right way round, so the current enters the collector and exits the emitter.

author: cwalex
author_rank: Frequent Contributor
timestamp: January 28, 2014, 11:10:27 pm
content: if the arduino and the treadmill control board share a common ground then I don't know why you would need to add any extra components like relay or optocoupler to simulate button press unless you need some sort of isolation ??
Simulate Mosfet Ringing in LTSpice - Page 1
Forum section: electronics / beginners

author: Tomsik
author_rank: Contributor
timestamp: June 26, 2019, 08:18:55 pm
content: Hello, I'm trying simulate ringing on mosfet transistor by LTspice, but I'm not able to do...Please help me

author: MagicSmoker
author_rank: Super Contributor
timestamp: June 26, 2019, 10:07:09 pm
content: There's actual several possible reasons why you can't see ringing. First is that the rise and fall times for the pulse are both set to 1u - that's way too long to excite ringing between the MOSFET capacitances and the stray inductances; try setting that to 20n.Second is that you are measuring the voltages outside of the resonant networks; measure the actual drain and gate voltages, instead.Third is to set a minimum timestep in the simulation command to something appropriate for the frequencies you expect to see, though note that this greatly increases simulation time; try 100n first, then 10n if you still don't see ringing.EDIT - forgot one, which is the most elementary of them all: the strays are overdamped by the resistances, so no ringing will occur. Though you'll likely to some overshoot on the source terminal.

author: Tomsik
author_rank: Contributor
timestamp: June 27, 2019, 08:46:58 am
content: I've set rise and fall edge to 20n and set the simulation timestep to 100n a then 10n. Still not ringing.Sorry, but i don't understand your last sentence...

author: MagicSmoker
author_rank: Super Contributor
timestamp: June 27, 2019, 09:50:48 am
content: Quote from: Tomsik on June 27, 2019, 08:46:58 amEach inductor you added forms a series resonant network with the relevant stray capacitance of the MOSFET, but also in series with those resonant networks are resistors which dampen the ringing. That is to say, as the damping resistance in a series resonant network increases, the amplitude of the ringing, and the time it takes to decay completely, decreases*. In the case of the BSP89 MOSFET you picked, the .model directive shows it has a gate-to-source capacitance (Cgs) of 70pF and a drain-to-source capacitance (confusing referred to as Cjo) of 10pF. The characteristic impedance is determined from the formula (L/C)^0.5 which comes out to around 12 Ohms for the gate LC network, but the series resistance is 50 Ohms, so this LC network is definitely overdamped (in fact, with such small LC components I doubt you'll see ringing even if the gate resistor was reduced to 1 Ohm).I'll leave determining the drain and source node characteristic impedances to you as an exercise, but note that ringing at these nodes really only occurs during turn-off, not during turn-on (for another exercise, try to figure out why).* - and for a parallel resonant network the damping resistance is in parallel, with ringing amplitude decreasing as resistance is decreased, so the inverse of the series LC network.
Simulating a motor driver in ltspice with DRV8701 gate driver - Page 1
Forum section: electronics / beginners

author: no1no2no3no4
author_rank: Newbie
timestamp: February 03, 2024, 11:47:16 pm
content: Hi, I have some questions about a circuit I'm simulating in LTspice. This circuit is designed to drive a 12 volt brushed DC motor using the DRV8701 gate driver and CSD88537ND NMOSFETs. I'm definitely a beginner but as far as I can tell I've set this up properly according to the datasheets but I'm not getting the results I expect. In the current configuration, I would expect there to be a constant 12 volts applied across my motor(just a 10ohm resistor) but it's just hovering around 0. I've attatched my .asc and .libs for the ICs(the models come directly from TIs website). Does anyone have some wisdom that could help me here? I'm also not sure what the ppad pin is as it does not appear in the datasheet. Thanks in advance!
Simulating coilgun both electrically and physically - Page 1
Forum section: electronics / beginners

author: mkaluza
author_rank: Contributor
timestamp: June 04, 2024, 05:39:45 pm
content: Hi,I know, not another one, but bear with me hereThe main goal of this exercise is to learn stuff, not just randomly stiching together some caps, wires and a triggerI want to be able to simulate a coilgun fairly accurately in order to be able to then feed that simulation into an optimization algorithm to see what I can get. So everything is done programatically in python.The problem with simulating the physical and electrical parts separately is that FEMM can't do transient sims and it assumes a constant current, and simulating an RLC in LTSpice doesn't take into account the changing inductance. So to get any reasonably realistic results you need to simulate it simultaneouslyI assumed that it would be easier to run RLC 'by hand' and let FEMM do the heavy filting and not the other way around...Initially I assumed that coil inductance depends only on the position of the slug relative to it. I also assumed that the force the field exerts on the slug at given position is only dependent on current. I know both of those assumptions break down as we approach saturation, so we'll just stay away from it for now. With those assumptions I simulated a slug moving through the coil at 1A current in FEMM (coilgun_prep.py - requires pyfemm). That gave me L(x) and F(x, 1A) curves (coilsimres.json).Then I load those curves, interpolate and use them to solve equations for both position/speed of the slug and coil current (coilgun_sim.py).I modeled the movement as dx/dt = v and dv/dt = F(x, i)/m - for F(x,i) I just do i * F(x) since F(x) was calculated for 1AThe coil was modeled as du/dt = -1/C * i and di/dt = -R/L(x)*i + u/L(x). But... I'm not sure how to incorporate the fact that the coil is changing inductance, and this also influences current. I approached it like this: given the coil has some energy E, if it inductance changes, the resulting current would be changed by a factor of sqrt(L_prev/L_current).... but I suspect it's wrong and could use your input here...Obviously that is just a first approach - but I could really use some help with the coil/magnetic part - I can't really 'feel' it (pun intended)
Simulating ICs in Proteus - Page 1
Forum section: electronics / beginners

author: Frongach
author_rank: Newbie
timestamp: October 03, 2018, 04:34:17 pm
content: Hi guys,First post here. I'm having trouble simulating ICs in Proteus. I tried even a quite basic 555 timer circuit, and still no joy. Sorry for the general question, but can you spot anything wrong in the setup attached, someone mentioned to be careful about power supply to the chip, I tried battery and injecting a voltage as here, but neither got the circuit running in any case. The output at pin 3 just stays high here by the way,Thanks a million,Brian

author: txescientist
author_rank: Regular Contributor
timestamp: October 03, 2018, 08:23:13 pm
content: Hi,Try built-in examples. Attached you can find simulation I just made for you to test...

author: bson
author_rank: Unknown
timestamp: October 03, 2018, 08:45:12 pm
content: Welcome to the forum! Are all your nodes actually connected? I don't see any connection symbols (little black circles) for the two connections next to C1 and R1.

author: Rigolon
author_rank: Regular Contributor
timestamp: October 03, 2018, 08:57:29 pm
content: As bson said.C1 does not seem to be connected.

author: mc172
author_rank: Frequent Contributor
timestamp: October 03, 2018, 09:11:30 pm
content: It's been a long time since I used Proteus which is a shame because I really liked it! I seem to remember that you have got to set an initial charge value for capacitors otherwise oscillators will not start. Not sure whether the new versions require this, though. And as others have said, connect the components.

author: Frongach
author_rank: Newbie
timestamp: October 06, 2018, 01:07:48 pm
content: Hi,Thanks for your answers. I finally found that the problem was the 555 timer model in my version. I was originally trying to simulate a motor controller circuit for the TL494, and thought I'd try a simpler chip. In both cases, downloading a model was the solution..Brian
simulating insertion loss in LTSpice - Page 1
Forum section: electronics / beginners

author: Simon
author_rank: Unknown
timestamp: February 23, 2019, 11:13:10 pm
content: So i did the attached circuit and using the formula 20 log⁡√(1+(2πf/((R_S+R_L)/L))^2 ) calculated that at 100KHz i would have an insertion loss of 56 dB and at 1MHz an insertion loss of 76 dB. The simulation comes out with about 8 dB more loss with a 50 ohm load but with a 1K load is bang on. I assume this would be because "insertion loss" is what the filter (inductor) is removing from the otherwise unfiltered circuit but the simulation is giving me the output to input ratio and including the source resistance in the "filter loss" as it is not doing a filter loss calculation just an out to in.Is there a way of doing this as an insertion loss?Re running with a 0 source resistance still puts the numbers out

author: Simon
author_rank: Unknown
timestamp: February 24, 2019, 12:22:36 pm
content: Right i worked it out! As the insertion loss is the circuit before the inductor was added versus after it was added i have to take the source impedance into account and lump it with the load impedance. Doing this brings about the expected results.
[SOLVED] simulating multiple times the same circuit yelds different results - Page 1
Forum section: electronics / beginners

author: not1xor1
author_rank: Frequent Contributor
timestamp: December 19, 2016, 09:14:25 am
content: Hi, I installed a couple of weeks ago LTspice on linux (kubuntu 14.04 + wine 1.6)in order to compare the efficiency of a linear power supply vs. linear power supply + mosfet pre-regolator I drew the circuit belowtoday I noticed that each time I run a simulation (now I just realized it happens with any kind of circuit) I get a slightly different result about the power generated by the "independent voltage generator" (50Hz sine wave) and, of course, of the dependent variablesis this my fault or a because of a stocastic factor added by design in the simulation?thanksp.s. I forgot to mention that .meas statements are already embedded in the asc file so you just need to read the simulation log for the results (Ctrl+L)---------------------------------------------The problem has been solvedit was probably due to a bug in a library shared with wine 1.6in the unlikely case might be of help to somebody else:after realizing that the executable installed in a virtual machine (xubuntu 16.04 in virtualbox) worked as expected, I wiped completely the current wine installation and hidden .wine dirreinstalling wine 1.6 did not solve the problem, but I had more luck with wine 1.8 and now can go on with virtually destroying electronic components in the simulator

author: danadak
author_rank: Super Contributor
timestamp: December 19, 2016, 11:10:48 am
content: I see output oscillating, couple that with finite machine arithmetic, algorithims,it will sim differently each time.How are you planning on load sharing to make sure one or more parts do notgo into thermal shutdown carrying too much load ?Regards, Dana.

author: not1xor1
author_rank: Frequent Contributor
timestamp: December 19, 2016, 01:44:47 pm
content: Quote from: danadak on December 19, 2016, 11:10:48 amI solved the problem (I'll add more details in my original post)now I get consistent resultsAnyway, I do not see any oscillations but just output ripplein the attachment below please compare the rectifier bridge output (a couple of volt peak-peak) with the linear regulator output (just few millivolts of ripple - Radj set to 5.06k e .step commented)Are you referring to that ripple?In any case please notice that this circuit is to be used just in simulations to check the power saved by inserting a wave-clipping pre-regulator, I never planned to build itfor that reason I did not mind about balance resistors at the IC outputsthanks
Simulating power supply schematic - Page 1
Forum section: electronics / beginners

author: pyroesp
author_rank: Regular Contributor
timestamp: August 07, 2016, 06:23:50 pm
content: I made the schematic below in LTSpice XVII, and everything seems to work like it should, but there's still something I don't quite get in the simulation...This schematic should be able to output 0-15V from a 0-5V signal and 0-5A current limit from a 0-5V signal.Probably best to use more powertransistors in parallel, but this is just a test.The schematic is set to limit the current at 500mA. With a resistive load of 10Ohms, the output voltage won't go higher than 5V.The simulation is set to DC Sweep of the V_set voltage from 0 to 5V.So here is what I don't understand. In the graph below you have Vfdb1 being the voltage at the output of U2 and Vfdb2 being the voltage after the voltage divider (1/3).Why does the voltage at Vfdb2 start to increase after the 2.5V mark on the horizontal axis, if the voltage at Vfdb1 does not increase?Am I just not seeing how the voltage at Vfdb2 can increase or is this a simulation issue ?Attached is the schematic, if you want to try it out.

author: StillTrying
author_rank: Super Contributor
timestamp: August 07, 2016, 07:09:14 pm
content: Quote from: pyroesp on August 07, 2016, 06:23:50 pmThat's what's supposed to happen with a 500mA limit.

author: pyroesp
author_rank: Regular Contributor
timestamp: August 07, 2016, 07:13:34 pm
content: Quote from: StillTrying on August 07, 2016, 07:09:14 pmI was just stating the fact that the power supply schematic seems to work correctly. Sorry for the misunderstanding.My question is about the voltage Vfdb2 in the graph.

author: StillTrying
author_rank: Super Contributor
timestamp: August 07, 2016, 07:26:05 pm
content: In that case U1 is struggling to keep both it's inputs at the same voltage, when the voltage difference gets big enough, current starts to flow in the input protection diodes.

author: pyroesp
author_rank: Regular Contributor
timestamp: August 07, 2016, 07:29:28 pm
content: When going into current limit, U1 can not get both input at the same voltage.I'll check the LT1002 datasheet to see if what you say is possible.EDIT: Well... should have checked the datasheet beforehand. From the simulation it looks like the voltage at Vfdb2 starts to rise at around a difference of 1~1.2V.The datasheet shows 2 diodes in series going from input to input, where current can flow through.@StillTrying: Thanks for the help.EDIT2: Added a diode between the voltage divider and negative input of U1. I can clearly see the voltage rising on the negative input and Vfdb2 staying at 1/3 of Vfdb1.

author: StillTrying
author_rank: Super Contributor
timestamp: August 07, 2016, 07:57:34 pm
content: Don't forget you can see the actual current flowing into an input by probing the edge of the op amp symbol where the input is. Now I've got the sim to run I can see up to 1.6mA flowing into +in and out of -in.
Simulating touch on a capacitive multitouch with a micro controller - Page 1
Forum section: electronics / beginners

author: victor
author_rank: Regular Contributor
timestamp: September 28, 2013, 04:12:37 am
content: Hello guys,I'm trying to simulate a capacitive touchscreen programmatically, I tried many ways of doing it, none seems to work properly. I taped down a piece of aluminum foil on the screen and attached a wire to a pin o an arduino board, and I toggled the pin LOW and floating. It kinda works, but is very touchy and hard to get it working.I'm very intrigued about this, because these multitouch are very very reliable, and it works flawless without never ever missing a single touch, works no matter what conditions, and I'm sure a human finger may have the eletrical characteristics dramatically changed, from person to person, works with your fingers wet or dry, etcBut I can't get it working nearly as good as a human finger, I'm pretty sure it can be done, but how? Any ideas?

author: Bored@Work
author_rank: Super Contributor
timestamp: September 28, 2013, 05:19:20 am
content: You could try to head over to eBay and look for specific capacitive touch screen styluses. There are a multitude of them, e.g.eBay auction: #271211093543,eBay auction: #121110821125. People use them if they e.g. wear gloves. Once you have them you could take a few apart, measure them, etc. to figure out what's the magic.

author: Paul Price
author_rank: Super Contributor
timestamp: September 28, 2013, 03:48:42 pm
content: A touch switch should be "very touchy".I made a touch control for a night lamp next to my bed for easy turn on in the dark. I used a PIC MCU analog input pin and was easily able to detect the presence of a finger by measuring the analog voltage changes (house mains body pickup) using a software scheme that only allowed a verifiable press if the touch persisted for a 2-second or more interval and then it did not allow a second press until the press changed voltage was no longer detected and a software debounce timer(1-sec) had run out, so only then it was ready for another touch.I used a 10-meg resistor on the analog input pin and a Schottky diode to VDD and ground to protect the input pin and the analog voltages were all over the place when a finger was applied, yet max and min volts were small enough to detect that there existed a non-touched condition.

author: amyk
author_rank: Super Contributor
timestamp: September 29, 2013, 11:21:40 am
content: First of all your touch contact is way too big - it needs to be around the size of a fingertip.Secondly, it's sensing touches due to changes in capacitance, and these changes are *very* small - the length of wire between the MCU output and the screen is probably more than enough to cause stray electromagnetic fields to induce voltage and affect it.