hybridfree/eevblog-posts huggingface dataset:
Switch mode PSU failed. Need help repairing. - Page 1
Forum section: electronics / beginners

author: Nick9one1
author_rank: Newbie
timestamp: August 14, 2019, 10:14:14 am
content: I nearly posted this in the repair section for the forum, but as I'm a beginner it's probably better here...I have a smps from a Reebok treadmill. The treadmill doesn't appear to power up at all.I've ordered a complete set of caps, tested the diodes and bridge rectifier. The coil also seems to be good.I've got as far as testing the DC output of the bridge rectifier.What should I do next?Thanks!

author: Wimberleytech
author_rank: Super Contributor
timestamp: August 17, 2019, 01:30:02 pm
content: Find out which SMPS chip is used.Download the datasheet for that chip.The example application schematic in the datasheet is probably close to what you have on your board.Identify and check each component in the power supply circuit--using the schematic as your guide.Replace the chip of all other components check out ok.When testing the supply you probably need to load it in order for it to work properly.

author: ratatax
author_rank: Regular Contributor
timestamp: August 18, 2019, 01:44:31 am
content: Most smps have a double diode with common pin in a mosfet-like package, usually on a heatsink like the switching mosfets. You can check if it's not shorted.

author: stevelup
author_rank: Regular Contributor
timestamp: August 21, 2019, 06:30:37 am
content: Which bridge rectifier? The big one on the heatsink, or the little round one?The stuff on the heatsink that you have removed has nothing to do with this unit powering up - that's all the drive for the main motor.The power supply part of this board is the bit by the 8 pin DIP package.
Switch mode PSU noise and ocilliscopes. - Page 1
Forum section: electronics / beginners

author: davelectronic
author_rank: Frequent Contributor
timestamp: September 13, 2021, 12:35:12 pm
content: It's taken me a long time to get round to some electronics testing. I purchased a second hand Hameg ocilliscope which is 60Mhz CRT old style ocilliscope. The purchase was mainly for testing switch mode power supply noise, and then possibly put a filter together to attenuate any unwanted noise on the output of smps. I've looked around for an answer, as to whether this ocilliscope is suitable for seeing these noise wave forms. I know a modern storage ocilliscope is ideal, but could the old Hameg 60Mhz ocilliscope show me these noises until I can get a modern storage ocilliscope. Thanks for reading, any thoughts appreciated.

author: tunk
author_rank: Super Contributor
timestamp: September 13, 2021, 12:43:12 pm
content: I've been using a 20MHz CRO for this and it works fine.You may have to adjust the trigger level to get it to trigger.And to better find Vpp you could switch it to the slowesttime base.

author: tggzzz
author_rank: Super Contributor
timestamp: September 13, 2021, 06:52:06 pm
content: In this kind of cases, the difference between analogue and digitising scopes is less important than the difference between good and bad probing techniques.

author: davelectronic
author_rank: Frequent Contributor
timestamp: September 13, 2021, 09:07:36 pm
content: This is good news, I know I can't capture anything as it doesn't have storage function ability. Thank you for your replies, just got to set it up now..
Switch Mode Regulator Battery Discharge - Page 1
Forum section: electronics / beginners

author: vargoal
author_rank: Regular Contributor
timestamp: December 19, 2016, 08:36:17 pm
content: Hi,I am currently trying to design a switch mode supply into a project I am working on. Looking at a energizer 9v datasheet (http://data.energizer.com/PDFs/522.pdf) there is different battery capacity based on current draw which makes sense. My question is what current draw would be accurate to use for a switch mode supply. For example to create a 5v rail at 1 Amp output will have a peak draw of 2 Amps. But as the supply is switching there will be times when no current is being drawn. Should I just use the average current draw or should I assume the maximum? I don't know which way is most accurate and I can't seem to find anything online about it. Does anyone know anything about how battery discharge works with switch mode supplies that can shed some light on the problem?Thanks

author: Gyro
author_rank: Super Contributor
timestamp: December 19, 2016, 08:54:53 pm
content: There's no way you're going to be able to source that amount of power from that battery for any significant length of time, sorry. Also, to achieve maximum life your supply would need to be able to operate down to an end voltage of 4.8V, probably lower given the high load.

author: Benta
author_rank: Super Contributor
timestamp: December 19, 2016, 10:23:46 pm
content: Normally, a DC-DC converter should have an input capacitor, so the current draw from the supply/battery is (mostly) free from switching artefacts.The power drawn from your battery can then be calculated from (output power/efficency), and from there, input current can be calculated easily.However, a design without an input storage capacitor is marginal at best.Exceptions are DC-DC converter topologies with a serial inductor at the input: Sepic or CuK. These are rare, though (but excellent!).
Switch power between 2 IC's using ground leg with a button press - Page 1
Forum section: electronics / beginners

author: L10N37
author_rank: Newbie
timestamp: July 05, 2021, 05:51:00 am
content: Hi guys,I'm being really lazy asking here instead of doing my own research but I want to know how to accomplish the following for as cheap as possible, and smallest as possible. Hoping for a single IC solution.I want to be able to flick between 2 separate IC's being active, without using a manual SPDT or respective push button switch.I was thinking, tie them both to VCC but route the ground legs through an IC that has inputs, and a common output for the ground that switches internally, the switching which can be triggered by pulling the other legs low momentarily i.e (it's a gaming console) push for example 'L1/ R1 / select' at the same time (thus pulling those inputs low) and then switching which legs is being passed to the grounded common pin thus rendering one IC active and the other inactive and vice versa.Cheers**I have arduinos on hand if someone can point me in the right direction (relevant programming examples)

author: JustMeHere
author_rank: Frequent Contributor
timestamp: July 05, 2021, 07:48:39 am
content: You're looking for a flip-flop.https://en.wikipedia.org/wiki/Flip-flop_(electronics)

author: L10N37
author_rank: Newbie
timestamp: July 05, 2021, 09:06:09 am
content: Thank you

author: ledtester
author_rank: Super Contributor
timestamp: July 08, 2021, 03:39:18 am
content: What are the two ICs and how are they wired to the rest of the circuit?

author: WattsThat
author_rank: Frequent Contributor
timestamp: July 08, 2021, 03:54:42 am
content: Low side switching will fail with devices that have inputs and other sources of voltage. It generally only works for single, simple devices like relays, led’s and similar types of loads.More info is required, as per previous post. Please explain what you’re attempting to do (in detail) and the devices used.
switch question - Page 1
Forum section: electronics / beginners

author: docmur
author_rank: Regular Contributor
timestamp: December 08, 2015, 04:22:50 am
content: Hey GuysI don't know what kind of switch this is, but I need to find a pushbutton switch that is just Mom, so you press it and it returns back, without holding.What kind of switch is this?ThanksDocmur

author: sleemanj
author_rank: Super Contributor
timestamp: December 08, 2015, 04:24:31 am
content: Momentary.There are a large variety of switches, so you'd need to be more specific about your requirements for anybody to guide you more than that.

author: IanB
author_rank: Super Contributor
timestamp: December 08, 2015, 04:25:18 am
content: Quote from: docmur on December 08, 2015, 04:22:50 amA momentary pushbutton switch?

author: docmur
author_rank: Regular Contributor
timestamp: December 08, 2015, 04:26:10 am
content: I thought that was what it was, but on Digikey I search for pushbutton but only see on-Mom, off-Mom and Mom-on-off. What I need is a small surface mount switch that is Mom.

author: alsetalokin4017
author_rank: Super Contributor
timestamp: December 08, 2015, 04:32:55 am
content: Quote from: docmur on December 08, 2015, 04:26:10 amWell, do you need it to be momentary ON (off except when pressed), or momentary OFF (on except when pressed) or alternating momentary ON and OFF when pressed repeatedly?If not otherwise specified, momentary ON is assumed.https://www.sparkfun.com/products/8720

author: docmur
author_rank: Regular Contributor
timestamp: December 08, 2015, 04:35:15 am
content: Well in this case once the button is pressed, the motor has to fire for 1 - 2 seconds, so I assume that's Mom-on? I know nothing about switches, thank for your help.

author: sleemanj
author_rank: Super Contributor
timestamp: December 08, 2015, 04:58:45 am
content: Is the switch directly powering the motor (needs high current) or is it driving a relay or transistor (needs low current)?You want a Normally Open Momentary Switch. In terms of digikey's nomenclature, "Off-Mom"If it's low current, any standard 6 or 12mm surface mount tact switch is what you want.

author: docmur
author_rank: Regular Contributor
timestamp: December 08, 2015, 05:00:11 am
content: The switch drives an int pin on the micro to trigger the motor drive
Switch Regulating a Fluctuating Voltage Input - Page 1
Forum section: electronics / beginners

author: brenesrob
author_rank: Newbie
timestamp: August 16, 2012, 04:41:48 am
content: I would like to use a switch regulator in order to regulate a voltage supply that changes from 17.5V when running off a solar panel and 7.2V when running off a battery. Is it possible to do this? The problem is that the inductor value for these circuits only covers a small range of voltages. I have used switch regulators in the past but for a fixed input voltage value not one that fluctuates over such a high range.The current being drawn by the load after the regulator is of 0.5A and I would like to keep the circuit as efficient as possible.

author: digsys
author_rank: Unknown
timestamp: August 16, 2012, 05:04:38 am
content: Quote from: brenesrob on August 16, 2012, 04:41:48 am7.2 > 17.5V is NOT a large range for MANY DC-DC converters at all. You didn't specify what OP voltage you need?If it is 6.0V or less, then your project is a piece of cake.

author: brenesrob
author_rank: Newbie
timestamp: August 16, 2012, 06:19:40 am
content: Sorry I forgot to mention it. My output voltage is of 5V for a USB connection.

author: Psi
author_rank: Super Contributor
timestamp: August 16, 2012, 06:54:09 am
content: http://www.digikey.co.nz/product-detail/en/R-78E5.0-0.5/945-1648-5-ND/2834904There's even a through hole module that has the typical voltage regulator pin-outhttp://www.digikey.co.nz/product-detail/en/OKI-78SR-5%2F1.5-W36-C/811-2196-5-ND/2259781Both look to be around 90% efficient
Switch terminology - Page 1
Forum section: electronics / beginners

author: msknight
author_rank: Regular Contributor
timestamp: June 21, 2021, 06:45:58 am
content: I know what I'm looking for... I just can't work out the terms I need to find it.On a joystick, I want a button/switch to mount on/in the joystick board, which allows me to invert an axis. Under normal operation, feed 1 goes to A and 2 goes to B. When "switched" feed 1 should go to B and 2 should go to A. Hence effective inverting the axis.But I can't work out the terminology I need for that kind of switch. Any ideas please?

author: Le_Bassiste
author_rank: Frequent Contributor
timestamp: June 21, 2021, 08:04:59 am
content: DPDT does the trick of "swapping" two connections.https://www.digikey.de/products/en/switches/toggle-switches/201?k=dpdt&pkeyword=dpdt&cur=EUR&lang=en

author: Ian.M
author_rank: Super Contributor
timestamp: June 21, 2021, 08:11:21 am
content: You need a DPDT (double pole, double throw) switch, also known as 2P2T switch. Seehttps://components.omron.com/pole-throwfor explanation of poles and throws.Wire it as a reversing switch, i.e. cross link pole A NC to pole B NO, pole A NO to pole B NC, then run the pair of connections you want to reverse through the switch, on one side connecting both to the A and B COM terminals, and on the other to the two linked pairs of NO and NC terminals.If you want to use a pushbutton it will need to be a latching switch, not a momentary one.

author: jpanhalt
author_rank: Super Contributor
timestamp: June 21, 2021, 09:38:48 am
content: There are 2 basic configurations of DPDT switches. Some have a center position ("off"). Others just switch between the two options. In addition, some hold the new position (i.e., there are 2 stable states) ; others are momentary on one state.I suspect you want an on-on version. Maybe this will do:https://www.digikey.com/en/products/detail/nkk-switches/YB26WCKW01/2107465EDIT: make that on/on "or on/mom" (momentary)If size is an issue. a single SPST momentary switch will probably be smaller and that could operate a DPDT relay.
switch to use with very small. battery powered, thin heater - Page 1
Forum section: electronics / beginners

author: counductivpr
author_rank: Newbie
timestamp: June 04, 2012, 04:08:19 am
content: Hello all,I have a very small thin heater I need to hook up in series to a battery and a switch. My battery ourput is 300 Ma with a peak of 700 Ma. Can anyone recommend a thin switch (like a momentary tactile switch) that will work like a rocker switch (remain on until pressed off)? Since a momentary switch has to be held down to stay on, it won't work for this project. I need the thin profile of a tacile switch, but the on/off capability of a rocker switch. Anyway to do this with a tactile switch or other switch?I know the output is a little steep for tactile switches as well. But this is a throw away piece and the life span is very short.Thanks,

author: ftransform
author_rank: Frequent Contributor
timestamp: June 04, 2012, 04:53:23 am
content: mind telling me what kind of thin heater you are using? I was actually looking for something like this... the best I could come up with is to snake around with nichrome..kinda curious about your project too.. defogging optics perhaps?

author: amyk
author_rank: Super Contributor
timestamp: June 04, 2012, 08:48:15 am
content: You surely mean 300 to 700mA, right? Several hundred million amps isn't easy to switchA relay and a tiny 6-pin MCU might work better, that way your switch doesn't need to see the full current and it can still be momentary.

author: metalphreak
author_rank: Frequent Contributor
timestamp: June 04, 2012, 02:38:48 pm
content: You can get clicky switches like the ones in generic PC cases (except not momentary). These ones are only rated for 500mA though:http://www.ebay.com.au/itm/10pcs-8-x-8mm-Capped-Knob-Self-Lock-Push-Tactile-Switch-/150820358058?pt=AU_B_I_Electrical_Test_Equipment&hash=item231d9807aa#ht_2194wt_1142

author: G7PSK
author_rank: Super Contributor
timestamp: June 04, 2012, 04:56:41 pm
content: If it is a throwaway unit it would not matter if the switch is over run it would likely last long enough anyway.

author: Time
author_rank: Frequent Contributor
timestamp: June 04, 2012, 05:11:35 pm
content: Should be very easy to find such a switch. Watch Daves videos that explain how to do parametric searches with Digikey, Mouser, and the likes.

author: mariush
author_rank: Super Contributor
timestamp: June 04, 2012, 05:17:13 pm
content: You mean something like this?http://www.digikey.com/product-detail/en/CUS-12TB/563-1102-6-ND/1124240http://www.digikey.com/product-detail/en/MLL1200S/450-1577-ND/1201378Plenty of similar switches like this on Digikey...

author: counductivpr
author_rank: Newbie
timestamp: June 04, 2012, 08:09:45 pm
content: Thanks for all the replies.Yes the output of the battery is mA. I got the heater from an aeronautical engineering firm to test for a project I'm working on. If they say I can release the name of the manufacturer, I'll reply and let you know. Thanks for all of the switch information. I'll make some purchases and get to work.Best,
switch with ways and poles lol - Page 1
Forum section: electronics / beginners

author: snipersquad100
author_rank: Frequent Contributor
timestamp: September 27, 2013, 06:51:47 pm
content: Can someone please explain to me the poles and ways on switches. Yes I am only a hobbyist.I'm making a simple signal generator and need a switch to switch between sine, square, triangle and integrator signals. what kind of switch can I get to do this? One on eagle cad would be nice as I'm be using this to design the circuit. Thank you

author: Rufus
author_rank: Super Contributor
timestamp: September 27, 2013, 07:49:18 pm
content: Quote from: snipersquad100 on September 27, 2013, 06:51:47 pmA 'pole' contact can be connected to one of a number of 'way' contacts.

author: kfitch42
author_rank: Frequent Contributor
timestamp: September 27, 2013, 07:53:06 pm
content: I think this is a reasonable description:http://en.wikipedia.org/wiki/Switch

author: andtfoot
author_rank: Unknown
timestamp: September 27, 2013, 07:53:46 pm
content: On a switch the number of poles is the number of separate circuits/signals being switched at the same time.The ways (or throws) is the number of positions that these circuits can be switched to/from.e.g. If you wanted to have 3 different signals being switched between 2 places (without the signals touching each other) you would have a 3 pole, 2 way switch.For what you are looking at I'd say a rotary switch would work well. You have 1 signal output that needs to switch between the 4 different inputs so you would look for a 1 pole, 4 way switch.Something like this (I'm not sure what shops you have over there; this is an Australian one):http://www.jaycar.com.au/productView.asp?ID=SR1210

author: w2aew
author_rank: Super Contributor
timestamp: September 27, 2013, 08:46:28 pm
content: Quote from: snipersquad100 on September 27, 2013, 06:51:47 pmNot to add to the confusion, but the "ways" is interpreted differently in the US when dealing with AC wiring (like in your house). Unfortunately, in this application the "ways" somewhat refers to the number of screw terminals. A 3-way switch, which is used to allow you to operate a fixture from two different locations, is really just a single-pole, double throw switch. But, it is called a 3-way. There's a 4-way switch which allows you to control a fixture from 3 or more locations, and it is really a double-pole, double-throw switch, with an internal cross-connect between the throws. So, "ways" does not equal "throws".In the US, switches used in electronics are always referred to by the the number of poles and the number of throws (not ways).

author: snipersquad100
author_rank: Frequent Contributor
timestamp: September 28, 2013, 08:54:58 am
content: Thank you guysandtfoot
Switchable high and low digital pin wiring - Page 1
Forum section: electronics / beginners

author: Duchy
author_rank: Newbie
timestamp: June 15, 2018, 10:42:14 am
content: A few months ago i made a very simple board housing 2 VND5025 load drivers in my offroad buggy, switching lights. and all worked well.I have very little idea as to what im doing, very new to arduino and electronics but now i want to make another, this time be able to talk to my link ecu (to turn on fans automatically via temp condition), which grounds its pins,Wanting to keep a simple design and have more circuits whats the best way to have 1 wire in than can either be connected to 12v switch like currently with voltage divider or set as digital low and shot the pin to gndIve attached a diagram of what i use for input now, but i want to combine the 2 so depending on where the wire in plug goes ( 12v switch or ecu ) i can change it in code.I hope this makes some form of sense
Switching 12V with 28V, 12V with 3.3V (mosfet?) - Page 1
Forum section: electronics / beginners

author: namlu
author_rank: Contributor
timestamp: February 18, 2015, 08:50:27 pm
content: Hello.Both 12V output voltages should be able to drive at least 1A load. Load is unknown. Should be like "voltage source". As if I put voltage regulator / relay.1) I want to switch 12v with 28v pin. 0v output if 0v input, 12v output if 28v input. I made it with voltage divider of 28v to 12v, and then a simple CMOS buffer (two cmos inverters - nmos and pmos x 2). Seems to work. Is it ok that I used voltage divider, or voltage divider should not be used in "real circuits"? Any other way to do it?2) switching 12v with 3.3V FPGA output. How it is done? I could not figure out. In pmos - if vg=0 or vg=3.3, and vs=12, both times vgs<vthreshold. Any good way to do it?Thank you.Sent from my iPad using Tapatalk

author: suicidaleggroll
author_rank: Super Contributor
timestamp: February 18, 2015, 09:03:37 pm
content: 2) Use an NMOS to isolate the line. PMOS gate is pulled high and connected to NMOS drain, NMOS source connected to ground, NMOS gate is pulled low and connected to FPGA pin. FPGA pin is low or high impedance, NMOS is off, PMOS gate is pulled high, PMOS is off. FPGA pin is high, NMOS is on, PMOS gate is pulled low, PMOS is on. Just make sure you use an NMOS with a Vgs threshold below 2v or so to ensure it's good and on at 3.3v.You could do the same thing for #1 as well, provided the NMOS you use can tolerate a Vgs > 28v.

author: Whales
author_rank: Super Contributor
timestamp: February 19, 2015, 12:25:22 am
content: For (1) I presume the last buffer is supplying the output power, so the voltage divider is fine as it won't be affected by the load you put on the output.
Switching 3Kw 240v heating with low voltage 24DC thermostat - Page 1
Forum section: electronics / beginners

author: spinach
author_rank: Newbie
timestamp: March 28, 2018, 09:21:54 pm
content: Hi All,I wanted to ask the opinion of others about this project.I have a spare Smart thermo (Tado with extension box) that I'd like to use to control 2x1.5Kw 240v heating with a spare Tado thermostat and extension box.I was thinking about using the following:https://www.mouser.co.uk/ProductDetail/528-6240AXXSZS-DC3https://www.mouser.co.uk/ProductDetail/528-SSR-HS-1https://www.mouser.co.uk/ProductDetail/528-SSR-TP-1putting it inside a large junction box and switching the low voltage side with the smart thermostat. The mains will come from an RCD already in place and there will be a fused switched spur before the junction box.What do you think?

author: Zero999
author_rank: Super Contributor
timestamp: March 28, 2018, 10:20:47 pm
content: That will work, but why have you decided on a solid state relay, rather than a mechanical one?The solid state relay you've chosen is much more expensive and will have higher power losses, than the equivalent mechanical relay. The only advantages are: more resistance to vibration and the life is not limited by the number of cycles. If it's not being switched very often and isn't subject to vibration, then a mechanical relay is a better choice.

author: spinach
author_rank: Newbie
timestamp: April 04, 2018, 02:18:11 pm
content: I decided on an SSR because of the frequency it's going to turn on and off. From what I know about this particular thermostat it works on a demand for heat scale, which determines how frequently it turns on and off. I've noticed my boiler which is also on the same brand of thermostat can be on for a few minutes then off for a few minutes.It looks like I've either broken it, have a damaged unit or don't understand the wiring but it doesn't work.I have terminal 2 connected to the AC live, terminal 1 connected to the heater live, and the AC neutral and earth connected directly to the heater. When I turn on the power the power led on the heater comes on for half a second then goes off.

author: spinach
author_rank: Newbie
timestamp: April 04, 2018, 08:38:20 pm
content: I managed to figure it out. After reading around the internet I hooked up my bench power supply to the DC side of the relay, and an incandescent lamp bulb to where the heater connects. Increasing the voltage slowly on the bench supply, the lamp came on at just over 19v. So the relay requires quite a bit more than the stated minimum 3v to work.
Switching a 9VDC supply by sensing a voltage? - Page 1
Forum section: electronics / beginners

author: K3mHtH
author_rank: Regular Contributor
timestamp: December 23, 2020, 07:02:56 am
content: Hey guys,I think this is an easy problem, but I don't know what to call it so I'm unable to search.I have a battery powered 9VDC circuit that is connected to a larger piece of equipment (I'm going to call this "the mothership" from now on). To save the battery life, I'd like to shut off my circuit when the mothership is turned off.One of the wires going into my circuit connects to the Mothership's positive rail (+15V) through an internal 10K resistor. Ground is also connected between the two.I feel like this voltage going to 0V when the Mothership is turned off could be used to cut the battery power to my circuit. Maybe using a mosfet or something?My circuit draws about 200mA when on and I'm OK with there being quiescent current being drawn from this solution, I'm sure it will be a lot less than 200mA!

author: Hugo Balls
author_rank: Newbie
timestamp: December 23, 2020, 08:08:12 am
content: Search query "battery switch off circuit"Q1 can be replaced by bipolar npnI would also put a 10k-ish resistor to ground from its gate

author: fordem
author_rank: Regular Contributor
timestamp: December 23, 2020, 01:55:32 pm
content: A relay with the coil powered from the mothership is quick & easy.

author: K3mHtH
author_rank: Regular Contributor
timestamp: December 23, 2020, 06:57:04 pm
content: Quote from: Hugo Balls on December 23, 2020, 08:08:12 amThanks Hugo, this circuit looks ideal.When I'm speccing out the P-Channel MOSFET to use for this, what specs am I looking for? Does the MOSFET power dissipation need to be higher than the power that my circuit will be using for example?

author: Hugo Balls
author_rank: Newbie
timestamp: December 23, 2020, 07:55:48 pm
content: In this case power dissipation would depend on the mosfet drain-source resistance when it's open (RDS(on)) and current flowing through it - R * I2so lower - bettereralso don't forget the voltage drop across it - R*I (Ohms law FTW)other parameters to be considered here is maximum drain to source and gate to source voltage - which is 9V battery here most will handle itso look for Rdson-price-package

author: jesuscf
author_rank: Frequent Contributor
timestamp: December 24, 2020, 12:09:56 am
content: Something like this using BJTs may work:
Switching a circuit by resistance - Page 1
Forum section: electronics / beginners

author: holographicpencil
author_rank: Newbie
timestamp: November 19, 2015, 02:45:24 am
content: Hello there,I'm sure this is a bit of dumb question but I haven't yet found any answers.Basically I have a sensor that changes its resistance proportionately to temperature and would like to make a circuit that goes 'High' when a certain resistance is reached.I feel like this should be both a common and also simple thing to do but I cannot think how to do it and would appreciate any inputThanks in advance

author: xrunner
author_rank: Super Contributor
timestamp: November 19, 2015, 02:51:31 am
content: Think "voltage divider". As the resistance increases or decreases across one resistor (the sensor) it will start to drop more or less voltage than the other stable value resistor. You can use that as the input to the next stage.

author: Connoiseur
author_rank: Regular Contributor
timestamp: November 19, 2015, 03:35:37 am
content: You can feed the voltage xrunner pointed out, to a comparator or a Schmitt trigger, to get the required high or low state. Use Schmitt trigger if you want a bit of hysteresis in order to prevent any oscillations during transition.
Switching a Triac - Page 1
Forum section: electronics / beginners

author: IvoS
author_rank: Frequent Contributor
timestamp: April 21, 2015, 09:36:01 pm
content: I will be using this triac:http://www.mouser.com/Search/ProductDetail.aspx?R=BTA24-800CWRGvirtualkey51120000virtualkey511-BTA24-800CWand this opto to drive it:http://www.mouser.com/Search/ProductDetail.aspx?R=MOC3023Mvirtualkey51210000virtualkey512-MOC3023MThe triac is switching 2 x 300VA toroidal transformers hooked up to 120V.Looking at the MOC3023 datasheet I am not sure if I should use the 39ohm resistor in series with 0.01uF capacitor for snubbing the triac. The triac I want to use is snubberless....And how about the 0.05uF capacitor between 360 and 470 ohm resistor for snubbing the optocoupler? Do I need it? The datasheet says "it depends".Thank you for your help.
Switching Audio Signals?  - Page 1
Forum section: electronics / beginners

author: Lewham5115
author_rank: Newbie
timestamp: September 11, 2024, 05:23:55 am
content: I have a project where I will have two guitar pedal effects circuits in the same project enclosure and I would like to be able to turn each one on independently of eachother, but also to change their order in the signal chain, in addition to being able to have them both in series or parallel.So something likeIn - - Effect A - - Effect B - - OutIn - - Effect B - - Effect A - - OutIn - - Effect A - - Out- Effect B -With four switches, one to turn each effect on and off, one to change between series and parallel order, and one to reverse order of the circuits when they are in series.But I'm struggling to wrap my head around how to achieve this. Having the series/parallel switch is what's really messing with me.Can this be achieved with mechanical switches? 4000 series logic? Do I need some sort of microprocessor to control relays?Any help would be greatly appreciated.

author: Andy Chee
author_rank: Super Contributor
timestamp: September 11, 2024, 05:27:39 am
content: 4066 analog switches would've been my goto device for this application.But maybe there's a modern device people use nowadays?

author: magic
author_rank: Super Contributor
timestamp: September 11, 2024, 05:40:45 am
content: IMO it would bealmostOK to have the following switches, which could be simply mechanical:Select A-in between In and B-out (SPDT)Select B-in between In and A-out (SPDT).Enable mixing A-out into Out (SPST). (I presume that mixing is what you mean by "parallel effects".)Enable mixing B-out into Out (SPST).One disadvantage of this is that it becomes possible to run the two effects in a loop, disconnected from the input. Hell knows what will happen then, but likely nothing good

author: gcewing
author_rank: Regular Contributor
timestamp: September 15, 2024, 11:12:21 am
content: 3-position 3-pole rotary switch.Two of the poles select the input source of each effect (circuit input or the output of the other effect).The third pole selects the output (effect A, effect B, or both through summing resistors).A inputB inputOutputA->BInABB->ABInAParallelInInA+B
Switching battery between Charger and Circuit - Page 1
Forum section: electronics / beginners

author: amallaburn
author_rank: Newbie
timestamp: January 17, 2021, 10:36:09 am
content: Backstory:I have partly built a portable boombox using a 12v 7AH battery, cheap amp and couple speakers.Made one a couple years ago (https://www.instructables.com/Portable-Boombox-1/) but downsizing this one, building out of acrylic and going back to lead acid rather than Li-Ion.Little infoI'm going to have a charging port on side with abarrel connectorthis will be charged via anImax B6 (Genuine)set to charge 12V.When the battery is charging the circuitdoes notneed to be active as beingcharged at homeandused outdoorswhen up in hills.Questions:I have previously done this using aDPDT switchwith anON-OFF-ONsetting, it worked fine on previous project just wondering if there is abetter way of doing this?I switched both the Positive and Negative on theprevious one.Ideally wanting to install a rotary switch do I have toswitch both positive and negative?Have attached a schematic I made in word,to make things simpleI have justused a bulb instead of my circuithave also used a ON-ON DPDT switch in schematic

author: Microdoser
author_rank: Frequent Contributor
timestamp: January 17, 2021, 11:39:51 am
content: Yes, you would need to switch both wires, + and -. I would also say to make sure the device and the charger are both turned off when you switch.Usually, the charging voltage is higher than the voltage of the batteries, often a 12V battery will be charged at 13+V. You may want to check the exact voltage your batteries need to be charged at in order to get a good amount of charge in them and what precautions are advised regarding when to stop charging etc.

author: ledtester
author_rank: Super Contributor
timestamp: January 17, 2021, 12:14:02 pm
content: I don't see why you can't have a common ground for everything.I would set it up like this:In fact, with the right type of barrel plug you can have the process of connecting the charger automatically disconnect the battery from the boombox circuit. See this stackexchange answer explain the use of a "switched jack":https://electronics.stackexchange.com/questions/90529/what-to-do-with-third-contact-in-dc-barrel-plug-with-only-two-input-contacts

author: Microdoser
author_rank: Frequent Contributor
timestamp: January 17, 2021, 12:57:46 pm
content: Quote from: ledtester on January 17, 2021, 12:14:02 pmTrue, it's not required (which was the actual question asked). My personal preference is for designs that completely isolate all paths to circuits not in use. I have some old habits hanging on from dealing with high amperage DC circuits where leaving a path to ground can be dangerous if you slip with a screwdriver etc.It's not required for normal functioning though.
Switching battery through load - Page 1
Forum section: electronics / beginners

author: Frongach
author_rank: Newbie
timestamp: January 18, 2019, 09:39:53 am
content: Hi there,I'm working on a circuit based on Adam Welch's 18650 capacity tester :; where a logic-level mosfet switches the positive terminal of an 18650 through a power resistor to ground. I am trying to switch the mosfet out for a darlington npn transistor (TIP102), but can't get it to fully switch. I have a feeling the battery polarity is somehow creating a high side switch type situation, but just can't figure it out.I've tried it with lower value base resistors too. I'm using an ATtiny85, it puts out 5.5v and can source 40 mA.I've a attached a rough schematic, I'd really appreciate any help. I was thinking to put a pnp there but I'd like to understand what's going on also...Thanks a million,Brian

author: Ian.M
author_rank: Super Contributor
timestamp: January 18, 2019, 12:06:42 pm
content: It depends on the definition of 'fully switch'. A Darlington can never have a Vce voltage drop of much less than one volt across it (compared to 0.2V to 0.3V Vce for a saturated single transistor), because the output transistor of the pair cant turn on harder than that without reducing the collector voltage of its driver transistor to the point the output transistor starves itself of base drive.A MOSFET can get right down to 0V Vds, as there are no junctions in its channel. In practice Vds wont be zero as it will have *some* on resistance so if any significant current is flowing there will be some voltage drop, but it can be pretty close to zero at lo to moderate currents, with some MOSFETs having on resistances down in the few tens of milliohms region when their gate is driven hard enough.

author: spec
author_rank: Frequent Contributor
timestamp: January 18, 2019, 03:05:46 pm
content: Hi FrongachThe 18650 LiIon battery is shown on your schematic as having a terminal voltage of 4V, but the terminal voltage for LiIon batteries when not on charge is 3V6.You have a 10R load resistor so the maximum current that could ever bee drawn from the battery (if you replaced the TIP100 darlington with a switch) is 3V6/10 = 360mA.A TIP100 will have a VCE saturation voltage of around 0.8V at around 360mA, so that means that there would be 3V6- 0.8= 2V8 across the 10R resistor, so the current flowing through the 10R resistor will be 2V8/10R = 280mA.In summary the VCE of the TIP100 will be 0.8V and the current through the 10R resistor will be 280mA. I bet that is what you have got.What are you aiming at. If you give us a specification we can probably advise on a solution.https://www.onsemi.com/pub/Collateral/TIP100-D.PDF
Switching between battery and usb power. - Page 1
Forum section: electronics / beginners

author: Kaisha
author_rank: Contributor
timestamp: August 25, 2021, 02:22:19 am
content: I need a circuit that will switch between USB and battery power (USB if available, battery otherwise). The thing is that in this case the battery will be a higher voltage (6.5V-9.5V) than the USB, so the 'normal' method show online doesn't work. I also only have a SPST switch to turn the entire thing on/off (which is connected to VBAT).I think the circuit below will work, but I'd love another set of eyes, and any input/ideas you guys might have.

author: ledtester
author_rank: Super Contributor
timestamp: August 27, 2021, 03:53:16 am
content: Here's a similar EE StackExchange discussion:https://electronics.stackexchange.com/a/96070/95488

author: vu2nan
author_rank: Contributor
timestamp: August 27, 2021, 09:20:39 am
content: A 5V electromagnetic relay may be used to switch between USB and battery.Nandu.

author: Zero999
author_rank: Super Contributor
timestamp: August 27, 2021, 12:38:25 pm
content: Quote from: vu2nan on August 27, 2021, 09:20:39 amThat will work, but there needs to be a fairly big capacitor between +V Out and 0V, otherwise there will be a huge voltage sag, when it switches. You probably need to limit the voltage drop below 0.5V.The minimum capacitance depends on the switching speed of the relay, the maximum allowable voltage drop and maximum current drawn by the device.C = Δt/ΔV×IAlso note the voltage drop due to the ESR of the capacitor.Make the capacitor a little larger, than calculated by the formula above.

author: Peabody
author_rank: Super Contributor
timestamp: August 27, 2021, 02:11:28 pm
content: Would the battery voltage ever be lower than VUSB? If it's ever more than one diode drop below VUSB, then USB current would flow through the body diode of the P-channel back to the battery. You might not want that to happen.Would you ever need to operate the device from USB with no battery connected? If so, then the P-channel gate would be floating. I don't know if that matters if there's no battery.It's not clear to me what purpose Nchan3 serves. It seems the diode should be enough.
switching between different inputs - Page 1
Forum section: electronics / beginners

author: carbon dude oxide
author_rank: Frequent Contributor
timestamp: September 18, 2013, 04:23:54 pm
content: hello, i have a small project that i would like to ask a few questions oni have a vga monitor that i would like to have two devices display onto it and internal vga and external vga (inside my cabinet and an external connector outside) i would like it to switch between the two is a specific way.when there i nothing connected to the external vga connector i would like it to automatically switch to the internal vga and when something is connected into the external connector i would like it t switch to it even if the internal vga is outputting something kinda like an override switch. how would i g about doing this using solid state methods? (i dont want the annoying clicking of a relay each time it switches

author: carbon dude oxide
author_rank: Frequent Contributor
timestamp: September 18, 2013, 04:30:40 pm
content: im thinking for the detecting that an active device is plugged into the external vga conector is to use a micro to read the voltage on the SDL/SDA line and when it is high it can then decide that there is something plugged into it and allow the switch

author: Lightages
author_rank: Unknown
timestamp: September 18, 2013, 04:40:54 pm
content: I am not sure that it is worth you trying to design and construct such a device when they are available to purchase like this one:http://www.misco.co.uk/Product/137374/Lindy-2-Port-VGA-Auto-Switch

author: carbon dude oxide
author_rank: Frequent Contributor
timestamp: September 18, 2013, 04:57:33 pm
content: im going to be making it with multiple different connectors, (VGA,DVI,HDMI,SCART and many others i just chose VGA as a starting point) i do plan on having this as a singular unit
Switching between two battery packs - Page 1
Forum section: electronics / beginners

author: Mp3
author_rank: Frequent Contributor
timestamp: November 23, 2020, 11:32:37 am
content: I'm looking to have a little project box powered by either two AA's or a single 18650. It only draws about a half amp (little Arduino device) so either is safe to use.What i'm wondering is how to switch between the two battery packs safely....Surely if one of the battery bays is unoccupied, it's not much of a concern. But, what if the switch was flipped while both battery bays were occupied?Is it sufficient to put diodes on the switch or should i add additional protections like a relay?

author: Doctorandus_P
author_rank: Super Contributor
timestamp: November 23, 2020, 12:15:52 pm
content: Most dual pole switches open before before they close (on the other side)If your switch is guaranteed to to this, then there is no need to even put diodes in series (which introduce a voltage drop which is quite significant at low battery supply voltages).But during the time the switch is switching (a few milli seconds) your circuit does not get any power at all. Because the time is so short however, it can be bridged by a decent capacitor.If you want some automated switching so the circuit is always powered when at least one battery is inserted, then ad (skottky) diode on each terminal is the simplest option. In that case you can add a (bistable) relay that bypasses one of the diodes to eliminate the voltage drop.

author: Mp3
author_rank: Frequent Contributor
timestamp: November 23, 2020, 12:26:54 pm
content: That helps a lot. Thank you!
Switching between two DC supplies with polarity protection using common return - Page 1
Forum section: electronics / beginners

author: x4ce
author_rank: Contributor
timestamp: December 20, 2024, 02:22:09 pm
content: Dear,I have a setup where I need to connect an external power source of 12V & a 4S battery with common return (negative). I got a PCB with following schematics of each source which has polarity protection along with switching of power i.e. 12V supersede 4S. But, the intended circuit is not working. When I connect both 12V and 4S, a short-circuit is observed. There could be something that is missing.Please help/ guide in identifying issue.Appreciated!Regards

author: m k
author_rank: Super Contributor
timestamp: December 28, 2024, 02:18:58 pm
content: What have you measured?

author: jwet
author_rank: Frequent Contributor
timestamp: December 28, 2024, 07:42:44 pm
content: Unfortunately, there is a big hidden body diode between source and drain. These kind of circuits that want to allow bidirectional current flow need two back to back MOSFET's. Just google for back to back n channel low side for battery isolation. Hopefully you can salvage what you have and add a FET. Good luck.edit: original has "source and gate"

author: Konkedout
author_rank: Frequent Contributor
timestamp: December 28, 2024, 08:43:50 pm
content: Quote from: jwet on December 28, 2024, 07:42:44 pmI think you are referring to the drain body diode between source and drain, not source and gate. When you use a normal MOSFET for ORing control (or as a synchronous rectifier) your normal conduction is generally reversed from using the MOSFET as a switch. So a Pch drain will be positive relative to source, and an Nch drain will be negative relative to source. The drain body diode will then conduct in the direction that you want to conduct anyway.https://www.vishay.com/docs/68934/si7149dp.pdfI strongly recommend that you replace your MOSFET box symbols with correct, complete MOSFET symbols which include those diodes. That will help you to see the error of your ways...

author: jwet
author_rank: Frequent Contributor
timestamp: December 29, 2024, 01:24:35 pm
content: Correction made- thanks
Switching between woofers & tweeters with switch - Page 1
Forum section: electronics / beginners

author: Adhith
author_rank: Frequent Contributor
timestamp: October 03, 2017, 05:44:15 pm
content: hello everyone...I'm planning to build a portable speaker which consist of two woofers and two tweeters fed from 2 passive crossovers to drive the right and left channels. I feel that at low volume the woofers is not having much bass but at higher volume its fine. I also noticed that while directly connecting the woofers to the amplifier a much better performance is seen but upon increasing the volume the sound gets distorted. Since I use the speaker indoors and outdoors I need to get better performance at lower and higher volume, so I decided to connect a DPDT switch for the audio output from the amplifier to turn on only the woofer at lower volume and both woofer & tweeter at higher volume. I came up with a circuit but don't know it works or not. So could anyone help me out, the circuit is attached below

author: katzohki
author_rank: Frequent Contributor
timestamp: October 03, 2017, 07:48:35 pm
content: So when you have it switched one way you have the output going directly to the "woofer" and when you have it switched the other way the output goes to the crossover input. Looking at the crossover as a black box it appears reasonable, but I don't really know what you've got in there.

author: Adhith
author_rank: Frequent Contributor
timestamp: October 04, 2017, 03:57:46 pm
content: Quote from: katzohki on October 03, 2017, 07:48:35 pmThank you for your support katzohki. In the schematics only the output terminals are shown. Woofer tweeter COM & input are the exact connection pins on my croosover
Switching Buck module on a esp32 protoboard - Page 1
Forum section: electronics / beginners

author: MrOmnos
author_rank: Frequent Contributor
timestamp: July 03, 2020, 05:08:17 pm
content: I am designing an esp32 protoboard with esp32 wroom module with several I2C connections points for different sensors. I am using the bare module with no power circuit. I would like it to have the capability to operate with 12v lead acid battery or 12v solar power supply. For 12v to 5v and then 3.3v conversion I am using 7805 ic and ams1117 respectively. Its cheap readily available but wastes too much precious energy. I am thinking of implementing a fixed 5v buck convertor on the board. Something like this.Board is quite small so I need to consider the size and also the cost. But I have a concern that the buck converter is going to mess up or interfere with wifi and other circuit. I would like to know if it is a good idea to do this and do you guys have any advice on design considerations I should take. I would also like your valuable advice on the type of switching IC I should use if anyone has any experience with similar project, please share.Thank you

author: JustMeHere
author_rank: Frequent Contributor
timestamp: July 04, 2020, 03:36:39 am
content: I've built a couple boards with buck converters. As long as your converter isn't running near the WiFi frequency you should be fine. Proper grounding is important. The board I did with a ground plane (4 layer) has almost no noise. The other one uses a star ground. You will have more problems with your IO pins if your grounding is bad.