hybridfree/eevblog-posts huggingface dataset:
digital power switch design - Page 1
Forum section: electronics / beginners

author: KTP
author_rank: Frequent Contributor
timestamp: September 20, 2010, 09:15:56 pm
content: My wife wanted a single button control for the flashing bike flag light circuit I built for her using the MSP430 and some 3 watt leds. I came up with this simple circuit which allows a single momentary switch to both turn on and turn off the power to the system and also function as a digital input to the MSP430 as well (to control the pwm (brightness) of the leds for example). Breadboarded, the circuit works as expected, and seems to consume nanoamps if anything when powered off (leakage current of the pmos). I suspect I do not really need R1, as the opto transistor would just have the dc current through R2 plus the pulse current from discharging the gate capacitance of the pmos, and anyway, the base current is limited by the light from the led in the opto which should limit the collector current as well. But in any case, 100 ohms works as is.The circuit is very basic...when the momentary switch is pressed, the pmos gate is pulled low causing the channel to conduct, supplying power to the 3.3V regulator which in turn causes the msp430 to power up. The first line of code in the MSP430 outputs a high signal on the latch line which activates the opto which keeps the pmos gate pulled low even after the momentary switch is released. During normal power on operation of the MSP430, pressing the momentary button pulls the microcontroller line low (msp430 internal 47K pullup turned on). This is where D1 and D2 come into play. D2 keeps the opto from pulling the microcontroller input line low and D1 prevents the msp430 from seeing the battery voltage through the 10K resistor R2 (not sure exactly what this would do...possibly without D1 the MSP430 would power up slightly through the 10K resistor and it's pullup logic even with the pmos off).Anyway, as always, appreciate any comments on improvements although it seems to work perfectly as is. To turn off the power to the system requires the momentary switch to be held down for greater than 1 second, which the msp430 monitors using one of the timers. Another added benefit is by using the watchdog timer with a slow input divided clock, the bike lights will auto shut off after about 2 hours.Just seemed like a useful beginner circuit to share.

author: Zero999
author_rank: Super Contributor
timestamp: September 20, 2010, 11:03:27 pm
content: Seems overkill having an opto-isolator, why not use an NPN transistor?Of course an even easier option would be to use a regulator with an enable or disable pin which can be connected to the MCU output.

author: KTP
author_rank: Frequent Contributor
timestamp: September 20, 2010, 11:37:55 pm
content: Quote from: Hero999 on September 20, 2010, 11:03:27 pmI didn't have a regulator with a enable pin in my junkbox (this was a total junkbox quick build) but I see looking at them that they have an acceptable shutdown current (1uA). The opto was overkill...it was already on the breadboard from a previous project so I just used it instead of a 2n2222 or something
Digital Rheostat - Page 1
Forum section: electronics / beginners

author: ngauger
author_rank: Newbie
timestamp: October 01, 2014, 08:31:20 pm
content: I hope this is the right forum. I am trying to find or define a digitally controlled rheostat or voltage controller. Ideally there would be a four to eight bit digital input and the voltage output would be proportional across standard house voltage 0 to 120 v. I want to use it for a light intensity or dimmer circuit. I have been unable to find such a commercial product. I have attached a generic circuit I found but I lack the knowledge to pick an appropriate opamp or determine the various resistor values. Hopefully, this interests someone who can help.

author: kxenos
author_rank: Frequent Contributor
timestamp: October 01, 2014, 09:42:29 pm
content: Welcome to the forum. This circuit is for DC. For 120VAC you need a dimmer with triac. A digital dimmer is a rather difficult circuit for someone to start exploring electronics.

author: ngauger
author_rank: Newbie
timestamp: October 02, 2014, 07:45:17 pm
content: kxenosThanks for the input. I did not pick this design as a random place to start with electronics. I am a model railroader and am looking for something to meet a function I desire for the hobby. Do you have some suggestions of where to look for existing designs or even commercial manufacturers. Of couse, I am looking for something relatively cheap. Thanks again.

author: Seekonk
author_rank: Super Contributor
timestamp: October 02, 2014, 08:10:30 pm
content: I would seriously think about using a UNO if you need multiple control. I get these microcontrollers shipped from China on ebay for about $8 and they are pretty easy to use. For AC lighting you want to purchase AC solid state relays that are NOT zero voltage switched, that means you can trigger them on at any time. That will allow you to make a phase angle control for light dimming. If you have low voltage DC lamps, simply drive a FET and use one of the UNO PWM pins.

author: Paul Moir
author_rank: Frequent Contributor
timestamp: October 02, 2014, 08:27:47 pm
content: Take a standard light dimmer, replace the pot with a CdS cell and put it back together. Now you have a light controlled light dimmer. Couple the CdS cell with an LED and feed the LED from a DAC or even a 2R2 resistor ladder. The ladder might make more sense because you could play with resistor values to get the right light output per step. You may want to drive the ladder with something like a 74HC244 or if you want latching an 74HC573.Alternatively you could PWM the LED if that's easier than the DAC.
1st Digital signal analyzer - Page 1
Forum section: electronics / beginners

author: rena
author_rank: Contributor
timestamp: April 11, 2022, 12:49:39 pm
content: Hello, I’d like to buy my first digital Logic analyzer to work on old digital effectors you find in recording studio (eventide, lexicon…).I have the opportunity to buy a Rigol DS1052D or a HP54645D.Does anybody have any recommendation about those models please ?

author: tepalia02
author_rank: Regular Contributor
timestamp: April 21, 2022, 11:25:18 am
content: This one has a quite reasonable pricehttps://www.sparkfun.com/products/18627

author: rstofer
author_rank: Super Contributor
timestamp: April 21, 2022, 03:47:47 pm
content: The DS1052D is a 50 MHz scope, the HP is 100 MHz. It may be possible to unlock the Rigol to 100 MHz, ask over in the Test Equipment forum.Then make a spreadsheet of capabilities for comparison. Band width (unlocked?), sample memory size, maximum sample rate and so on.It's too bad you can't get a deal on the Rigol DS1054Z or the Siglent SDS 1104X-E as these are 4 channel scopes and quite handy for decoding things like the SPI protocol.

author: rena
author_rank: Contributor
timestamp: May 02, 2022, 12:25:02 pm
content: Thank you for your advice !I took the HP since it was quite cheap.I will start with it a buy something better if I feel the need.Thanks again !

author: exe
author_rank: Unknown
timestamp: May 02, 2022, 05:12:30 pm
content: Perhaps I'm too late to the party. Probably, both will do fine for a beginner. There are a few things that I'd like to mention. Rigol has 5x the sampling rate. Also, I have doubts that 100MHz are useful at 200Msps due to aliasing. Physically, rigol is much smaller and more shallow (judging from the pics, didn't compare specs), leaving more space on the table (unless you use shelves).
Digital Steady-State Error for a Ramp input - Page 1
Forum section: electronics / beginners

author: sspj9
author_rank: Contributor
timestamp: November 06, 2019, 10:46:04 pm
content: Since the stead-state error is given by:Hence X(z) = G(z)*U(z) where U(z) = (0.2z^-1)/(1-z^-1)^2 Which is the ramp input in Z-domain at Ts=0.2.This would simplify to xss = lim(z->1)[(z^-1)/(1-z^-1)G(s)] However substituting z=1 in denominator would yield infinity...This is definitely not the case as in my simulation there is a slight steady state error.What am I missing here please?
Digital switch - Page 1
Forum section: electronics / beginners

author: Tetris911
author_rank: Newbie
timestamp: January 22, 2023, 01:59:32 am
content: Hello everybody, I'm new to this forum and am looking forward to learning more about electronics and getting help with projects.Speaking of help I'm building a simple ESP32oscilloscope designed by Jobit Joseph on the Circuit Digest website.I'm looking to replace the regular switches (SW1 and SW2) in the analog front end with some kind of digital switch that would let me cycle though the settingswith button pushes. Thanks in advance foe any help!

author: james_s
author_rank: Super Contributor
timestamp: January 22, 2023, 02:10:18 am
content: A relay controlled by a transistor is the most obvious solution that comes to mind.

author: ledtester
author_rank: Super Contributor
timestamp: January 22, 2023, 02:15:03 am
content: Yes, using relays is generally what's used in oscilloscopes. See this StackExchange discussion:https://electronics.stackexchange.com/questions/465202/relay-inside-oscilloscope-relay-vs-other-switches

author: jbeng
author_rank: Regular Contributor
timestamp: January 22, 2023, 02:46:43 pm
content: Quote from: james_s on January 22, 2023, 02:10:18 amI would think that's about the only way to do it without putting a limitation on the amplitude of the input signal.Just about any solid-state switching would likely be limited by the power supply voltages of the switching devices.

author: pcprogrammer
author_rank: Super Contributor
timestamp: January 22, 2023, 02:57:48 pm
content: Check out the schematics of the FNIRSI 1013D and the Hantek DSO2D10 given in these links:https://github.com/pecostm32/FNIRSI-1013D-1014D-Hack/blob/main/Schematics/1013D/Scope_Analog_Input.pnghttps://github.com/pecostm32/Hantek_DSO2000/blob/main/Schematics/Mainboard/Analog_Input_1.pngBoth use a mix of mechanical relays and solid state switches to control some of the settings. The solid state one is used for AC/DC select.

author: Infraviolet
author_rank: Super Contributor
timestamp: January 22, 2023, 08:52:04 pm
content: Something like a 74HC4066 or similar IC? More compact than a relay and lower power requirements, but will only tolerate small currents on through the switching element. These sort of analog switch ICs also won't cope with higher voltages (some types 5 volts, others might handle 12), but as your oscilloscope's core is an ESP I assume you aren't going to be measuring larger voltages with it?
Digital to analog audio converter - volume output adjustment - Page 1
Forum section: electronics / beginners

author: Mad Professor
author_rank: Regular Contributor
timestamp: June 06, 2014, 02:02:56 pm
content: Good day all.I have been asked to look into if it is possible to adjust the volume output on a optical digital to analog audio converter.The unit works as expected, but even with powered headphones plugged into the converter the volume output is below the desired level.I have had a quick look inside the unit, as it seems that it is using a 4558 Dual Operational Amplifier, for the headphone output.Now I have never done any work with op-amps before so I am not really sure where to start.I will try and take some pictures and get them up here asap.Can you please advice.Thanks for your time.Best Regards.

author: Richard Crowley
author_rank: Super Contributor
timestamp: June 06, 2014, 02:24:16 pm
content: Quote from: Mad Professor on June 06, 2014, 02:02:56 pmAssuming by the rest of the message that by "adjust" you actually mean "increase"? Likely many of us think of "adjust" as meaning user-controlled variable attenuation.QuoteDo the headphones work at a proper level when connected to other things?Do other things connected to the D/A converter operate at a proper level?QuoteIt may be premature to hack that circuit when the problem may be elsewhere. From the symptoms you have disclosed here, we can't tell where the problem may be. And since you have not revealed what any of the pieces are, we are limited to pretty much shooting in the dark.

author: Bassman59
author_rank: Super Contributor
timestamp: June 06, 2014, 07:15:31 pm
content: Quote from: Mad Professor on June 06, 2014, 02:02:56 pmThe output level is likely limited by:a) DAC power-supply railsb) amplifier current-source abilityc) headphone impedance.

author: Richard Crowley
author_rank: Super Contributor
timestamp: June 06, 2014, 10:46:30 pm
content: Quote from: Bassman59 on June 06, 2014, 07:15:31 pmThe Mad Professor said that he was using "powered headphones".His vague description does not allow us to determine whether the 4558 is in the DAC or in the "powered headphones".There isn't half-enough detail here to allow any kind of decent response to the questions.

author: linux-works
author_rank: Super Contributor
timestamp: June 09, 2014, 02:42:05 am
content: leave the dac alone and simply add a good phones amp.diyaudio and headfi are places to look for ideas on phones amps.
Digital to analog help. New here, anything appreciated! - Page 1
Forum section: electronics / beginners

author: AVcamp
author_rank: Newbie
timestamp: July 16, 2019, 10:54:39 pm
content: Hello!Looking for some help and advice with an automotive project. I'm trying to interface a new ECU with the original speedometer in the car.Original setup was a reluctor style sensor, frequency varies based on vehicle speed, 0hz to ~128hz. The speedometer board needs to see an AC signal, at least +-3v peak-peak relative to bat 0v to work correctly and is tolerant to >30v p-p. I have tested with a signal generator and it will take any kind of signal, square, sine, triangle, as long as it is in the correct voltage range and zero crossing.The output from the new ECU is a 0-12v square wave and the speedo board doesn't do anything with the signal.TLDR, looking for a way to level shift a 0-12v signal down to say a +-6v. Speedo measures at zero crossing point.I am very much a hardware person. Honestly not all that sure where to start, this is outside of the kind of electronics work that I normally (rarely) do. Would like to have this as simple as possible, discrete is good and just for simplicity would like to avoid using a micro.If there is anything else that I can add to help just say so. All for learning as much as I can, not in any kind of rush either.Thanks in advance!
Digital TV DIY antenna preamp. - Page 1
Forum section: electronics / beginners

author: dennisyuki
author_rank: Contributor
timestamp: June 21, 2015, 01:26:55 am
content: I live in the country. I built an antenna to pick up Digital OTA TV signals. I can pick up 2 stations. I know there are about 8 other channels in the UHF range that I could pick up but they are weak signals.I found a preamp project and did not know if this was the way to go. If not is there a better one?http://electronics-diy.com/wideband-dtv-uhf-antenna-tv-amplifier.phpAs I searched octopart for the 2sc3358 transistor. It does not look like a common part.So if the design is good, what would be a good subsitute tansitstor that I can get from digikey.I found the data sheet for the 2sc3358 but I do not know which are the important values to match to the new part and which values can I fudge on.data sheet..http://www.alldatasheet.com/datasheet-pdf/pdf/5863/NEC/2SC3355.html

author: NiHaoMike
author_rank: Super Contributor
timestamp: June 21, 2015, 05:33:53 am
content: Look at single chip RF LNAs. In particular, look for low noise figure. Also get a RTLSDR so you can plot the spectrum and figure out what you really need first.

author: continuo
author_rank: Frequent Contributor
timestamp: June 21, 2015, 07:20:39 am
content: What you really want to do is to improve on your signal to noise ratio. adding an a rf amp will add additional noise, that will take you nowhere (unless you have to use really long antenna cables, in which case you have to mount the amp right at the antenna, not in your living room). If you have to deal with weak signals, build or buy a better antenna with higher gain and use high quality, low-loss coax...

author: dennisyuki
author_rank: Contributor
timestamp: June 22, 2015, 06:49:49 pm
content: Quote from: NiHaoMike on June 21, 2015, 05:33:53 amThanks, I will check into the LNA. Also the RTLSDR looks interesting. Got to make time for another project.

author: dennisyuki
author_rank: Contributor
timestamp: June 22, 2015, 06:51:30 pm
content: Quote from: continuo on June 21, 2015, 07:20:39 amI relooked into antenna designs and I might try a bi loop antenna. (called a radial antenna?) thanks for the advise.
digital voltmeter conection for power supply - Page 1
Forum section: electronics / beginners

author: little_carlos
author_rank: Regular Contributor
timestamp: April 13, 2014, 05:54:15 pm
content: Hi, im trying to use a digital multmeter as a voltmeter for my powersupplyim using a 8v voltage regulator for supply the multimeter, when i measure something, like a 9v battery, it does fine, but when i try to measure voltage from the powe supply, just dont show anything, what im i doing wrong?

author: Richard Crowley
author_rank: Super Contributor
timestamp: April 13, 2014, 06:44:36 pm
content: Typically, DMMs require ISOLATED power. If you try to power them from what you are measuring, it may distort the measurement, or, even worse, it may damage the internal circuit of the DMM. NOT RECOMMENDED!Note that there some newer-generation digital panel meter modules which advertise that they CAN measure voltages in common with their power source. But they are specially designed to be able to do that. Absent any clue of which DMM you are asking about, it seems quite likely that your unit requires ISOLATED power.Those common-connection tollerant digital panel meters are so dirt-cheap that you could probably get a dedicated meter for your PS for less than it would cost to provide an isolated power supply to your DMM.

author: little_carlos
author_rank: Regular Contributor
timestamp: April 13, 2014, 07:24:17 pm
content: well, now i undertand why, thanks man
Digitally controlled step-up converter instead of using resistor feedback - Page 1
Forum section: electronics / beginners

author: DanioIO
author_rank: Contributor
timestamp: January 31, 2015, 11:24:48 pm
content: Hi,I need to control a output voltage from a step-up converter using a microcontroller is it possible to use a DAC instead of a resistor feedback in this case?

author: zapta
author_rank: Super Contributor
timestamp: January 31, 2015, 11:36:03 pm
content: You still need the feedback for the stabilization but you can inject signal from the DAC that influence it. What is your original circuit?

author: theatrus
author_rank: Frequent Contributor
timestamp: January 31, 2015, 11:40:15 pm
content: An op-amp summation stage from the feedback network with your DAC injected is one approach that would work for tweaking the value. Tweaking the ground reference point is another approach (though not directly from a DAC output).What is your circuit so far?

author: DanioIO
author_rank: Contributor
timestamp: February 01, 2015, 03:58:07 pm
content: Can this circuit do its job? I want to control LTC3862 which has a feedback reference set at 1.22V.

author: theatrus
author_rank: Frequent Contributor
timestamp: February 01, 2015, 04:52:55 pm
content: Your op amp is missing a feedback network but you have the right idea for a difference amplifier.
Digitech Oscilliscope  - Page 1
Forum section: electronics / beginners

author: irishshorty
author_rank: Newbie
timestamp: October 09, 2019, 02:52:43 am
content: Hi Allneed to know where im going wrong here just purchased an Oscilloscope for learning and have hooked it up to test port but cannot get square wave to show. no vertical lines as per attached image. Don't know if its faulty or not.

author: ataradov
author_rank: Super Contributor
timestamp: October 09, 2019, 04:09:02 am
content: It looks like you have dots mode enabled. Have a look in the settings. There is usually a configuration for the display mode.

author: irishshorty
author_rank: Newbie
timestamp: October 09, 2019, 05:51:58 am
content: Still the same problem, nothing ahem to work no horizontal lines on the test square wave

author: ataradov
author_rank: Super Contributor
timestamp: October 09, 2019, 05:58:43 am
content: So if you press Ctrl-V it does not change the display? What is shown in the Display -> Type ?Try to get a closer look at the edge of the signal. It is possible it just renders the signal this way, although I doubt it.

author: bob91343
author_rank: Super Contributor
timestamp: October 09, 2019, 06:00:09 am
content: It's normal to not see the transitions. They occur very fast. Digital 'scopes often have a 'connect the dots' function that shows those transitions.

author: ataradov
author_rank: Super Contributor
timestamp: October 09, 2019, 06:02:13 am
content: According to this scope manual Ctrl-V switches it to the vector display mode, which should "connect the dots". If it does not, then software is broken.

author: Cliff Matthews
author_rank: Unknown
timestamp: October 09, 2019, 11:46:21 am
content: This Hantek 6022BE rebrandedUSB scopewould work better with Horo's new opensource software:https://www.eevblog.com/forum/testgear/six-software-apps-to-use-with-the-hantek-6022be/

author: Gyro
author_rank: Super Contributor
timestamp: October 09, 2019, 11:57:46 am
content: Quote from: irishshorty on October 09, 2019, 05:51:58 amI think you mean no vertical lines btw.
Digitial Multiimeter Question - Page 1
Forum section: electronics / beginners

author: Vindhyachal.takniki
author_rank: Frequent Contributor
timestamp: January 31, 2015, 12:13:27 pm
content: 1. I am using digital mutilmeter for measuring voltmeter.It has 9V battery for multimeter operation.2. My question is when I use digital multimeter for voltmeter purpose, do black probe of multimeter is shorted to its internal 9V battery or both are isolated?

author: EEVblog
author_rank: Unknown
timestamp: January 31, 2015, 12:17:53 pm
content: Usually connected directly. Certainly not isolated because it doesn't need to be.Why do you ask?

author: electr_peter
author_rank: Unknown
timestamp: January 31, 2015, 12:50:08 pm
content: DMM red and black probes are most likely at +/- half voltage of the internal battery. DO NOT try to measure DMM's internal battery with same DMM probes - magic smoke will escape.

author: hamdi.tn
author_rank: Frequent Contributor
timestamp: January 31, 2015, 02:50:27 pm
content: i guess he's trying to power up the DMM from a lab power supply or any thing connected to main, and wondering about the probes being isolated.

author: Vindhyachal.takniki
author_rank: Frequent Contributor
timestamp: January 31, 2015, 03:23:05 pm
content: @EEVblog , I checked connectivity between black probe & battery GND using another multimter.They were not shorted together.I am trying to build a null detetctor as I have attached a circuit.1. GND of null detector & measuring ckt is different.2. I am planning to use ADS1248 (24 bit adc) to measure voltage drop across 100ohm resistor.3. Null detetor ckt is fixed I cannot make changes in it. I have to make my measuring circuit according to it.4. There are three points I have selcetd as in ckt: P,Q,R5. This leads to three cases, 2 of them are : +-(0.1uV - 100uV) , +-(0.1mV - 100mV).6. Third case leads to voltage : +-(100mV - 40V), I have break down it using 1 ohm resistor, so +-(1mV - 400mV)7. Any of three cases can come during functioning. So I have to do decision while reading data.I had asked this question as I want to short ground of my measuring circuit with null detector circuit. This will make measurement easy.That why I had asked if this can be done.I will switch the two gnds through relay & measure the result.

author: dannyf
author_rank: Super Contributor
timestamp: January 31, 2015, 04:32:49 pm
content: QuoteYou have lots of symbols on a chart. You don't have is a solid understanding of how you intended the circuit to work and why that requires the understanding of if a multi-meter's negative lead is connected to its battery negative terminal.I would suggest that you step back and ask yourself what you are trying to do.
Dim bulb question - Page 1
Forum section: electronics / beginners

author: GuntherM
author_rank: Newbie
timestamp: November 01, 2022, 08:13:43 pm
content: Hi all,this is an electricity question, I want to develop a dim bulb tester, with a lamp from 60w and a second one from 40w.What I have already, a variac, with in front a decoupling transformer from 240VAC.The variac gives supply to the dim bulb(s), now is the question, what kind of switch I'm going to need, to put between lamp 1 and 2? Why the split? I have enough 60w old stock lamps, but fewer from 40w.So I can put the lamps in series (100w), or decoupled (60w). The lamps also going to be used as load for a digital Volt and current meter.From there the current goes to an outlet, that comes out the cable gutter. The wooden plank, will be mounted against a wall, with self-made distance buses, to protect the cables on the backside.Look at the rough pictures I made, to get more sight of the project, the plank has to cut to a smaller format, also the cable gutter. And has to be painted as well, so it looks neat on my work bench.Of course, every safety rules going to be applied. It's just the switch that concerns me.Thank you for the help in advance.

author: IanB
author_rank: Super Contributor
timestamp: November 01, 2022, 08:40:09 pm
content: What is your question about the switch? Any mains rated switch would be fine. Are you asking how to wire the switch?

author: Gyro
author_rank: Super Contributor
timestamp: November 01, 2022, 09:34:59 pm
content: Quote from: GuntherM on November 01, 2022, 08:13:43 pmA small correction. You need to put the 60W and 40W inparallelfor 100W.

author: GuntherM
author_rank: Newbie
timestamp: November 01, 2022, 10:29:24 pm
content: The second time I made the same error on this forum, it's parallel indeed.So, a double pole switch will do the trick?

author: Gyro
author_rank: Super Contributor
timestamp: November 01, 2022, 10:37:34 pm
content: I would use two switches, then you can select 40W, 60W or 100W lamp configurations.

author: jeroen79
author_rank: Frequent Contributor
timestamp: November 03, 2022, 12:09:46 pm
content: Quote from: GuntherM on November 01, 2022, 10:29:24 pmDepends on what you want the switches to do.One switch, in series with the paralled lamps:-Acts as master power switch.-(Un)screw the lamps to set the power limit.-If this is a two pole switch you can switch out both the line and neutral.Two switches, each in series with a lamp, the switch-lamps in parallel:-Turns on the power per lamp.-Use the switches to set the power limit.-Only needs to be a single pole switch.One switch, parallel to the paralled lamps:-Bypasses the lamps so they do not impede any current.-(Un)screw the lamps to set the power limit.-Only needs to be a single pole switch.You can combine these.For example a master power switch, a switch to bypass the lamps and switches to set the power limit.
dimmer pack breakers always on - Page 1
Forum section: electronics / beginners

author: jaysgr
author_rank: Newbie
timestamp: October 03, 2015, 08:10:18 pm
content: Hello,As I am quite new in electronics and especially in dimmers, I could use some help in a problem I have.I have this dimmer pack shown in the picture (dmx 6ch dimmer pack), and when I plug the power, the lamp indicators of the breakers are on, even if the main power switch is off.It is like the main power is completely independent of the breakers.Is this normal?I read somewhere that the power switch turns on only the rest of the circuit, dmx etc..I would appreciate any help!Thanks!

author: David_AVD
author_rank: Super Contributor
timestamp: October 03, 2015, 10:30:54 pm
content: The single power switch only turns the electronics on/off. Otherwise it would have to handle the load of all channels.

author: Richard Crowley
author_rank: Super Contributor
timestamp: October 04, 2015, 02:27:50 am
content: Yes, it is normal. The switch only powers the CONTROL circuit, not the LOAD circuit(s).Else that would be an enormous breaker switch to handle the combined loads of all those dimmer channels!

author: jaysgr
author_rank: Newbie
timestamp: October 04, 2015, 08:28:53 am
content: Thank you very much for your answers!Very helpful and appreciated!That was what I was believing, I just wasn't sure.
DIN connector pin wiring question - Page 1
Forum section: electronics / beginners

author: richierich33
author_rank: Newbie
timestamp: October 28, 2016, 04:11:40 am
content: Hi - I have a quick question about DIN connectors and common wiring practice.I have a 120VAC AC-AC 12VAC wallwart power supply (for a laboratory balance) that uses a 5-pin male 180 degree DIN connector - but from my examination only the center pin (Pin 3) is connected to the 'hot' wire, with the shield being used as the neutral/ground.Is it common for companies to use 5-pin DIN connectors but only use a single pin for power? I assumed there would be several taps on the wallwart/tranformer with various voltages for each pin - but I cannot see any evidence of this. The other 4 pins have no connection that I can see. Is it possible that these other 4 pins are used as some sort of 'floating ground'?

author: NottheDan
author_rank: Frequent Contributor
timestamp: October 28, 2016, 04:53:36 am
content: Are you sure there it's more to it than the DIN being their standard connector and them not needing more pins on this particular application?

author: Brumby
author_rank: Unknown
timestamp: October 28, 2016, 05:25:32 am
content: Often, pin allocations are subject to the whim of the manufacturer - but it could be that a multiple pin connector could have different voltages on different pins.Equipment could be designed with different power requirements and by using the one connector set, the manufacturer could save on the cost of these through bulk purchase. It would have the advantage that, if your device needed 12V and you had a supply for some other product that provided a number of voltages, but provided that voltage on the correct pin, it would still work.Another possibility is that they got those connectors really cheap and just used them to do an undemanding job.
Diod across emitter and base? - Page 1
Forum section: electronics / beginners

author: u666sa
author_rank: Frequent Contributor
timestamp: December 18, 2024, 05:11:18 pm
content: Transistors are R25, and you are looking at VHF and UHF receiver tract. In stock form there are no diodes. But, someone just added them as part of a sensitivity mod. What is going on? What these diodes do?

author: madires
author_rank: Super Contributor
timestamp: December 18, 2024, 06:00:45 pm
content: BJTs have usually a base emitter reverse breakdown voltage around 5 V. The diode limits the reverse voltage to the diode's Vf drop and protects the BJT.

author: TimFox
author_rank: Super Contributor
timestamp: December 18, 2024, 06:01:31 pm
content: A diode from base to emitter is a common prophylaxis against reversing the base-emitter diode, for example during power-up.Even if the collector-base breakdown voltage exceeds 50 V, the base-emitter diode breakdown is usually only 6 V or so, and if that diode breaks down it reduces performance of the surviving transistor.Supposedly, one can "anneal" that damage by running large forward current through the base-emitter diode, but I have never tried that.

author: u666sa
author_rank: Frequent Contributor
timestamp: December 18, 2024, 07:38:59 pm
content: How does it relate to sensitivity?I see an improvement in replacing stock R25 transistors to BFU550AR, or BGA427's, and it's been done on same tract on different radio. But diodes, would that improve sensitivity? Stock sensitivity is around -116 dBm, and we want -130 dBm and better.

author: TimFox
author_rank: Super Contributor
timestamp: December 18, 2024, 09:35:29 pm
content: If anything, the parasitic conductance and capacitance of the added protection diode would make the sensitivity worse.Noise-critical applications sometimes have a switch to remove the diode after the operation as settled to avoid the effect.
diode across vcc & ground on fan header... - Page 1
Forum section: electronics / beginners

author: bigjoncoop
author_rank: Regular Contributor
timestamp: July 03, 2021, 05:32:21 am
content: hey my fellow DiYers,I have a PCB that was missing the components for an optional fan header that was not implemented from the factory. I installed the missing transistor and completed the signal path. now the circuit is working.but right next to the fan header Is a missing diode across Vcc and Ground... the fan circuit Works without it obviously and I'm assuming it is there so when the circuit turns the fan off, it doesnt backfeed voltage into the circuit while it still spinning for a few seconds... correct?should I install a diode or is it not a huge deal? and if so will any schottky blocking diode work? for instance a 1n5819 or 1n4007 If not what's the minimum value diode i should use?this is a 12v circuit and its a 40mm fan.thx

author: bobbydazzler
author_rank: Regular Contributor
timestamp: July 03, 2021, 07:06:19 am
content: I think you should install a diode - the fan can still be spinning fast when the power goes out and therefore has a bit of energy that can go the wrong way. 1n4007 should be fine.

author: Siwastaja
author_rank: Super Contributor
timestamp: July 04, 2021, 07:37:36 am
content: That is not what the diode is helping against.BLDC fans have internal half-bridge driver for each phase (typically 2 or 3 phases), these switches have implicit or explicit diodes for freewheeling the current stored in the winding inductance.Just a simple MOSFET, either on the ground or Vcc side, is often used to PWM these fans. I do have a habit of adding a freewheeling diode though but the purpose is to freewheel the (fairly small) amount of energy stored in the parasitic indutance of thewiring. It may indeed be completely unnecessary. I would suggest probing for any voltage peaks between the fan output pin and ground with an oscilloscope.
Diode after power switch - Page 1
Forum section: electronics / beginners

author: VoidIfRemoved
author_rank: Newbie
timestamp: June 30, 2015, 11:51:48 pm
content: I'm working on a project involving a microcontroller where I need it to consume no power when off, and then when the button SW1 is pressed the power switches on and stays on until the microcontroller sends the OFF signal. So far I have this. VCC is the power that comes from the battery, and V+ is the power going to the rest of the circuit (after having typed that, I've realized it'd probably make more sense to have those two labels switched, but I digress)Because the microcontroller is going to have a decoupling capacitor next to the power pin, I thought that I should put a diode after the toggle section so that the latching transistor will shut off properly and not be kept going by charge coming from the capacitor, and to generally isolate the toggle section from the rest of the circuit. Will this work as I'm thinking, and is the diode even necessary?Also, any feedback on the design in general would be appreciated.

author: Mr.B
author_rank: Unknown
timestamp: July 01, 2015, 12:06:06 am
content: Q3 is going to clamp your VCC to GND... Not a good idea.Read these two threads:https://www.eevblog.com/forum/projects/mosfet-power-switch-with-auto-off/https://www.eevblog.com/forum/projects/an-idea-for-soft-power-with-no-quiescent-loss/

author: retrolefty
author_rank: Super Contributor
timestamp: July 01, 2015, 12:26:00 am
content: Call me old school, but I always just used an inexpensive 5vdc single coil latching relay when I want or need manual on/auto off power control. Micro on startup just pulls a digital output pin low to latch power on and then brings the pin low when wishing to power off.http://img25.imageshack.us/img25/563/08miq7.jpg

author: ludzinc
author_rank: Unknown
timestamp: July 01, 2015, 12:27:34 am
content: Define 'no power'.When you can sleep a micro and have it draw uA, which gives you YEARS of operation on a coin cell, do you really need to go to ZERO draw?
Diode AND Logic; Pull Up Resistor - Page 1
Forum section: electronics / beginners

author: digitaleyes
author_rank: Newbie
timestamp: January 26, 2024, 02:52:01 am
content: I would like to build an AND module for my Eurorack, but I'm having trouble understanding how this circuit works.On Doepfer's DIY page, they say the following can be modified to their OR diagram to realize an AND circuit:QuoteI drew the following, but I have no idea what I'm doing.If this is correct, I'm completely perplexed. I copied the idea from what I gathered on diode logic on Wikipedia. Any help, thoughts, or suggestions would be great.TIAMike

author: sleemanj
author_rank: Super Contributor
timestamp: January 26, 2024, 03:17:05 am
content: If Input A is low, then current flows through diode A, pulling that node (and therefore output) to Vfwd of the diode (say 0.7v, 0.3v schottky).Similarly if Input B is low, same thing.If both input A and B are low, same thing.So that leaves where input A and B are both high, and you can see then that the diodes can not conduct (reverse biased) meaning that the output is high.NB: you have an extra ground/reference, center bottom of diagram, you're just pulling the output low permamantly with that, eliminate it.

author: digitaleyes
author_rank: Newbie
timestamp: January 26, 2024, 04:18:43 am
content: Like this?I guess that's one thing that concerns me when the voltage is low. Will all 12V pass through the diodes when either input is low? In my basic understanding, I would think this would cause 12V+ to come out of my jack and potentially damage the signal source.Thanks again

author: Andy Chee
author_rank: Super Contributor
timestamp: January 26, 2024, 04:26:03 am
content: Quote from: digitaleyes on January 26, 2024, 04:18:43 amAssuming it's correctly sized, the pull-up resistor will limit the current that is delivered through the diodes when the input is low.

author: digitaleyes
author_rank: Newbie
timestamp: January 26, 2024, 03:46:28 pm
content: Thanks for the feedback. I guess I'm going to dive in. I just bought a DC power supply and will soon get an oscilloscope. I want to learn all I can about electronics.So current = voltage/resistance. (let's assume I go off of the 5V power supply in my case with a 10K pullup resistor). This would then equal .0005 amps of current? And this must be a minuscule amount of current?I'm only asking because I don't know. I just looked up and saw that .1 - .2 amps can kill a human. Granted, that's 200- 400x the amount of current of .0005 amps. I don't want to kill myself once my power supply arrives.Quote from: Andy Chee on January 26, 2024, 04:26:03 am

author: Andy Chee
author_rank: Super Contributor
timestamp: January 26, 2024, 10:18:58 pm
content: Quote from: digitaleyes on January 26, 2024, 03:46:28 pmTheoretically speaking, 30mA (0.03A) AC current or 300mA (0.3A) DC current across the heart can kill a human.But human flesh usually has high enough resistance to prevent electrocution death from anything less than 50V, so I'm sure you'll be fine
Diode Behavior - Page 1
Forum section: electronics / beginners

author: Ducttape
author_rank: Regular Contributor
timestamp: November 15, 2016, 06:13:50 pm
content: I thought I'd hook up a trivial diode circuit to the scope just to make sure it does what I'd expect it to (newbie). Had a symmetrical ramp at 1kHz powering a 1k resistor in series with a 1N4004 diode, per the attached schematic. Channel 3 is voltage across resistor (ch1 - ch2). Looked as expected.Decided to up the frequency to 100kHz and got something not as pretty. What diode spec/characteristic is influencing the lagging voltage drop that allows reverse current flow?

author: rfeecs
author_rank: Frequent Contributor
timestamp: November 15, 2016, 06:33:45 pm
content: Reverse recovery time. Some datasheets list it:http://global.oup.com/us/companion.websites/fdscontent/uscompanion/us/pdf/microcircuits/students/diode/1n4004-general.pdfIt is caused by minority carrier charge storage in PN junctions. The amount of charge (and consequently the time) depends on the forward and reverse current.

author: nugglix
author_rank: Regular Contributor
timestamp: November 15, 2016, 06:51:25 pm
content: Hi!Nice video about that:Explains and shows whats going on.Great stuff, as usual.

author: Ducttape
author_rank: Regular Contributor
timestamp: November 15, 2016, 07:24:34 pm
content: Quote from: rfeecs on November 15, 2016, 06:33:45 pmThanks. My 'ON Semiconductor' datasheet doesn't include it, although I wouldn't have understood its significance before now.

author: Ducttape
author_rank: Regular Contributor
timestamp: November 15, 2016, 07:26:42 pm
content: Quote from: nugglix on November 15, 2016, 06:51:25 pmExcellent. And since I didn't know the term 'reverse recovery time' I probably would have never found it.

author: Audioguru
author_rank: Super Contributor
timestamp: November 16, 2016, 06:02:27 pm
content: The 1n400x are low frequency rectifiers (50Hz to 200Hz). The 1N4148 is a fast diode but it is smaller so its maximum current rating is lower.There are fast high current diodes available but I have never needed one so I don't know their part numbers.

author: David Hess
author_rank: Super Contributor
timestamp: November 17, 2016, 03:07:13 am
content: Quote from: Ducttape on November 15, 2016, 07:24:34 pmHuh, I was going to say that you must have missed it but I just checked and the ON Semiconductor datasheet is indeed missing any reverse recovery information for the 1N4004.Diodes also have forward recovery where they do not turn on instantly but it is of lessor concern because it is so much faster making it rarely specified.
Diode bridge - Page 1
Forum section: electronics / beginners

author: Remondepemon
author_rank: Contributor
timestamp: August 12, 2014, 07:23:27 pm
content: Hi everybody,I am building a power supply that needs 26V power for the analog part.Then, there is other stuff that runs on 12 and 5V.I could just use an 7812 & 7805 for it, but I don't want to dissipate so much heat.Plan B: What about using a transformer that has an extra pin in the middle?Then I need a transformer of 2x9 = 18V.For the high voltage stuff I use 2 secondary coils and for the low voltage stuff just one of the coils.Here is a schematic, can anybody please tell me if this will work or there will be smoke?Thanks!

author: Remondepemon
author_rank: Contributor
timestamp: August 12, 2014, 07:28:21 pm
content: whoops, an error in the schematic!

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 12, 2014, 08:05:52 pm
content: Not smoke, but if you put a cap on it, you'll get 26V+ again.....Take a close look at what the diode bridge is doing. The CT alone will be at 13V relative to the one-side-grounded bridge.Tim

author: Remondepemon
author_rank: Contributor
timestamp: August 12, 2014, 08:21:04 pm
content: Tim,I started to draw two separate bridges and discovered that 2 diodes were parallel. I deleted these two and then this schematic what there.What do you mean by CT and what would your advise be?Remon

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 12, 2014, 08:37:47 pm
content: CT = center tap, the middle of the winding.
Diode check - Page 1
Forum section: electronics / beginners

author: windmill john
author_rank: Contributor
timestamp: May 15, 2023, 10:29:27 am
content: I love forums, you can’t see my face go red when I ask a, possibly, silly question!…Our microwave started making a loud noise. Just out if interest, obviously safety was covered, one of the options online was to check the high voltage diode.I removed it and got no reading either way on diode mode on my dmm. I got no continuity either way on my dmm.Okay I thought, buggered diode. I then tried what the website suggested, actually using a 9 volt battery and performing the test again. This time I got a resistance reading one way but not the other; a good diode test….Okay, confused now. I’m new and have only tested small diodes for normal one way flow. How come this diode only showed flow with the battery attached?Is it something you do with it being a high voltage diode?Something else?The diode was an RG802.The video I saw was:https://diy.repairclinic.com/why-is-my-microwave-making-a-loud-noise/Cheers

author: PA0PBZ
author_rank: Super Contributor
timestamp: May 15, 2023, 10:36:10 am
content: Yes. high voltage diode, it is constructed with a lot of single diodes inside: --|>|--|>|--|>|--|>|--|>|--|>|--|>|-- Each single diode drops about 0.6V and your multimeter can't provide enough voltage to get a reading. Sounds like the diode is not the problem, maybe the tube has worn out. Did you check the window where the tube enters the oven cavity for dirt?

author: CaptDon
author_rank: Super Contributor
timestamp: May 15, 2023, 01:11:25 pm
content: Is it making a loud noise and failing to cook, or just making an unusual loud noise and working correctly? Very often prior to the magnetron tube failing it actually starts cooking the food even better!! Strange but true. I think when they start to get slightly gassy they begin to conduct at a lower voltage or perhaps conduct with more current. At any rate, when they suddenly seem to start working even better than new a major failure is in the near future. Inverter microwaves have a whole different set of weird things they do. Inverter microwaves are lighter without the huge iron power transformer and have a better power factor and somewhat less line current for the same cooking power. Another common magnetron failure is a short to ground at the filament connector. The plastic arcs through, burns a carbon path and shorts. Best wishes!!

author: windmill john
author_rank: Contributor
timestamp: May 15, 2023, 05:11:42 pm
content: Thanks both, you’ve given me the answer I needed.My electronics level is such that I would have been happy to replace the diode, but not fiddling with the magnetron.I didn’t test whether it could cook, the noise was enough! I wasn’t sure whether the noise hid other dangers, so it was bin time after testing the diode.Thanks again.