hybridfree/eevblog-posts huggingface dataset:
Reistor Rating - Page 1
Forum section: electronics / beginners

author: Rolf98
author_rank: Newbie
timestamp: January 17, 2020, 09:05:12 pm
content: I think i have caugh a case of beeing dumb. I am currently looking into what formula is the right one for calculating a Power ResistorI usally calculated them via V * A = WBut i also read about I^2*R = WIn my current circuit (An electronic load) which one would be correct as a load resistor.I am thinking it would be V*A because its the load. (Attached a pic. I circled it in blue. Yes i stole that picture of off google)

author: bob91343
author_rank: Super Contributor
timestamp: January 17, 2020, 10:06:27 pm
content: Both formulas are correct and yield the same result. See Ohm's Law.Having said that, in many cases one should take into account parasitic parameters such as stray capacitance, lead inductance, resistor inductance and distributed capacitance, etc. This is because a resistor isn't just a resistor any more if the frequency is high.But for dc or slowly variying stimuli, any of the formulas will suffice.If the resistor is nonlinear, a graphical method can work, or a wattmeter.

author: Vovk_Z
author_rank: Super Contributor
timestamp: January 17, 2020, 10:07:44 pm
content: P = I × V = I ^ 2 × R.The last one is Joule–Lenz law.

author: Vovk_Z
author_rank: Super Contributor
timestamp: January 17, 2020, 10:10:12 pm
content: And you can use 1 R resistors there, but it will lead to other changes.

author: Rolf98
author_rank: Newbie
timestamp: January 17, 2020, 10:35:07 pm
content: Oh god. Like i said i had a case of the dumbs today. Thanks for your help guys. Sometimes you just cant think in a straight line anymore. Had me stuck for like the last hour or more. so i just gave in and asked.Thank you very much for your Help
rel function on a fluke 83v - Page 1
Forum section: electronics / beginners

author: m3vuv
author_rank: Super Contributor
timestamp: September 15, 2019, 09:29:31 pm
content: hi all,may be a daft question but here goes,ive a fluke 83v multimeter,on resistance range if i short the probes together i get a reading of .3 ohm,so far so good,i then hit the rel button to zero it with the probes shorted,it then reads zero,all well and good,trouble is then it wont measure a resistance and the range button does nothing,is this normal or my meter iffy?,cheers m3vuv.

author: IVLRNR
author_rank: Contributor
timestamp: February 19, 2021, 06:44:05 am
content: haha. I see you have had no response in 120 days. So, I hope you figured it out. I too recently got hold of a 83V and am seeing some interesting issues. Which I will post here when I have fully discovered them; so that someone else might benefit from it. I have a feeling it could be the meter, lol.

author: tooki
author_rank: Super Contributor
timestamp: February 20, 2021, 01:50:09 pm
content: It’s normal. Rel mode in ohms fundamentally has two applications:1. zeroing out test lead resistance, which only matters for very low resistances. On any higher range it wouldn’t matter in any way.2. observing resistance change, which is typically within the same range.I’ll leave you to ponder the ramifications of that.
Rel, relative circuit - Page 1
Forum section: electronics / beginners

author: M0BSW
author_rank: Frequent Contributor
timestamp: March 09, 2013, 08:20:26 am
content: Hello ,One of my meters has the REL button which is really handy for precise measurement, the others do not and can have as much as 3 ohms, my question is it possible to make a stand alone REL circuit, to go between leads and meter, I guess the leads would have to be short between the meter and a rel circuit.I've try to search for a circuit to do this but no luck so far, it would be a good experiment if possible.thank youPaul

author: Unknown
author_rank: Unknown
timestamp: March 09, 2013, 11:33:42 am
content: You would need a circuit with a resistance of -3 ohm. Some circuits exhibit a negative resistance over a limited range, but I don't think any of them would work in this application. You could of course build your own resistance meter that outputs a DC voltage and uses the DMM as a display.

author: M0BSW
author_rank: Frequent Contributor
timestamp: March 09, 2013, 12:07:58 pm
content: Quote from: alm on March 09, 2013, 11:33:42 amSo am I right in thinking you would have to put in ohms to match the ohms of the leads to null or cancel it out.

author: SeanB
author_rank: Super Contributor
timestamp: March 09, 2013, 01:08:02 pm
content: No, you need to manually subtract the lead value off of the reading. You do not easily get a negative value resistor ( otherwise known as a battery) that is both adjustable and which will work in all multimeter circuits on all ranges.Basically just short the leads before using the lowest resistance range, then record that value at the time and subtract it from the reading. You will notice that this reading does vary as you remove and replace the test leads and will vary slightly with temperature. It really will only affect the lowest resistance ranges, and if it is 3 ohms you might want to try applying contact cleaner to the leads and the meter sockets ( a small amount using an ear bud to wipe the sleeve clean, it will come out dirty) and try again.

author: M0BSW
author_rank: Frequent Contributor
timestamp: March 09, 2013, 01:33:32 pm
content: Ok Sean, I made a resistor box when I connect to the none rel meter I have a reading of 0.3 ohms, with every thing at zero,when I dialed in 10 ohms it read 10.03/4, so taking the 0.3 off made it right now. that's that solved cheers.

author: SeanB
author_rank: Super Contributor
timestamp: March 09, 2013, 01:35:57 pm
content: Nice to hear that. Simple enough, and with a meter with relative reading the same applies about having clean connections.
Relation voltage-pressure in a differential  pressure sensor - Page 1
Forum section: electronics / beginners

author: raff5184
author_rank: Regular Contributor
timestamp: July 06, 2017, 09:29:25 pm
content: Hi all,I have an MPX2300DT1 differential pressure sensordatasheet:http://www.farnell.com/datasheets/2291651.pdf?_ga=2.13963191.1020306335.1499374310-1603013215.1499374310I am able to measure the output voltage but I don't know to which applied pressure it corresponds, how to "convert" the voltage to pressure. How do I retrieve this information from the datasheet?Thank you

author: Benta
author_rank: Super Contributor
timestamp: July 06, 2017, 09:44:19 pm
content: The datasheet is not very helpful, but as I know the Motorola/Freescale, now NXP pressure sensors well, here goes.The output is "Ratiometric to supply voltage", meaning that you'll need to give it a precise and steady supply. The output will vary with the supply voltage otherwise.It's specified at 6 V, so that's what you should aim for.The key parameter is "Sensitivity", listed as 5 uV/V/mmHg.If you enter the 6 V supply voltage into this spec, you'll get 30 uV/mmHg as the output.The zero pressure offset is pretty wide, so you'll need a true differential amplifier after the sensor.Hope this helps.EDIT: the voltage you need to measure is the difference between Out+ and Out-. The absolute value of those two voltages is somewhere around half the supply voltage.

author: raff5184
author_rank: Regular Contributor
timestamp: July 06, 2017, 10:01:35 pm
content: Quote from: Benta on July 06, 2017, 09:44:19 pmI have a DC supply, so no problemQuote from: Benta on July 06, 2017, 09:44:19 pmSo does it mean that an increment of 1 mmHg corresponds to an increment of 30 uV at the output?Quote from: Benta on July 06, 2017, 09:44:19 pmyou mean a differential amplif that amplifies the difference between Out+ and Out- otherwise it is too small to be measured?

author: Benta
author_rank: Super Contributor
timestamp: July 06, 2017, 10:10:51 pm
content: QuoteYou could put it like that. For every 1 mmHg de/increase in pressure, the difference between Out+ and Out- will de/increase by 30 uV linearly.QuoteI don't know what and how you need to measure this. I was just pointing out, that microvolt signals are normally not too useful, so if you need to amplify the output voltage (= difference between Out+ and Out-), a differential amp is needed, as the absolute output voltage is undefined.
relationship between input and output voltage of power booster circuit - Page 1
Forum section: electronics / beginners

author: khatus
author_rank: Regular Contributor
timestamp: April 10, 2024, 08:49:45 am
content: This is a power booster circuit. Here Q1 is a power transistor. I want to determine the relationship between input voltage(Vin) and output voltage (vout) here. and also want to determine Vout.I have found that,Here is my simulation. If the input voltage Vin = 15 volt The output voltage is fixed at = 13.28 volt i.e vout = 13.28. The VCC of transistor is 30 volt i.e VCC= 30 volt.the output voltage Vout is independent of transistor collector voltage i,e VCC. And if we increase the VCC from 30 volt to 50 volt the whole increased voltage (50V -30V = 20V) is dropped across VCE of transistor Q1.Please derive me the relation between Vin and vout. how 15 volt inputs give 13.28 volt output voltage. Please show me the calculation.

author: tooki
author_rank: Super Contributor
timestamp: April 10, 2024, 09:28:41 am
content: Normal op-amps need headroom between the supply voltage and the output. So if you’re only supplying the op-amp with +15V, its output will never reach +15V. Try giving it 17-20V.There are so-called “rail to rail” op-amps that can swing more or less to the supply voltages.

author: Zero999
author_rank: Super Contributor
timestamp: April 10, 2024, 09:54:18 am
content: The simulation results are correct.The op-amp is powered off 15V and its output can only swing to within 1V of its positive supply, which limits its output voltage to around 14V.Q1 is an emitter follower, which only boosts the current, not voltage. The emitter voltage is always about 0.7V less than the base voltage.This is why the output voltage saturates at about 13.3V.If you reduced VINto 1V, then the circuit would work properly and the output voltage would be 11V.
relationship between power and ground width track on PCB - Page 1
Forum section: electronics / beginners

author: amirkargar110
author_rank: Contributor
timestamp: September 10, 2017, 06:46:02 am
content: HELLOMY question is, the (power) "+" track width should be as wide as the "-" (or GND) width? if not what is the proportional between them(power and ground track width)?

author: Rerouter
author_rank: Super Contributor
timestamp: September 10, 2017, 07:48:59 am
content: The ground conductor should be sized to handle your expected current from any power rail, e.g. if your device had a 5V rail at 1A, and a 3.3V rail at 4A, your ground trace should be sized for 5A, or if you know you will never exceed 2A on those rails at any time, you could likely size it for 2A,If i recall this relates to your quadcopter ESC, as such if you cannot run the switching at 100% on (e.g. your mosfets will need a small off period before changing state, to prevent cross conduction) you can scale down to handle the expected average current.The final thing for sizing, the expected temperature rise calculators are expecting something stationary into static air, If you have forced airflow the temp rise becomes less (dissipated power remains the same), equally the trace width calculators are playing with wattage vs area, if you have a solid plane on the opposite side the temp rise drops again, as the copper traces radiate heat somewhat better than fibreglass. while having 2 hot traces on both sides of the board slightly increases the temp rise of both.
Relative mode and range on DMM - Page 1
Forum section: electronics / beginners

author: acinho
author_rank: Newbie
timestamp: November 30, 2015, 04:14:53 pm
content: Suppose I have a 5000 (ranges: 500mV, 5V) count dmm and I measure 4V. Now I press relative mode button and measure 4.1V.Display reads 100.0mV but what is the range I'm measuring in?500mV or 5V?

author: Kleinstein
author_rank: Super Contributor
timestamp: November 30, 2015, 04:18:46 pm
content: Usually the DMM is still in the 5 V range to measure and just substracts the starting point in the digital domain.

author: Wytnucls
author_rank: Super Contributor
timestamp: December 01, 2015, 06:14:57 am
content: The UT-71D (40,000 count) behaves in the same way. Top right shows the reading at the time the REL button was pressed. Top left shows the current reading and the main display shows the difference between the two, staying in the 4V range. The meter does not auto range anymore in that mode, showing OL above 4V.
Relatively simple Kirchoff problem with transistors! - Page 1
Forum section: electronics / beginners

author: pyrohaz
author_rank: Regular Contributor
timestamp: April 23, 2015, 02:12:10 am
content: Hi all,Its been an absolute age since I last did Kirchoff so I'm a little rusty. I'm trying to find the equations for voltage at two points in a simple circuit. Any help is appreciated!As a transistor is involved, I'm assuming I should use the small signal model where the transistor can be replaced for a behavioural current source (where the current is equal to Beta*ib). In my image, VBase would be driven by a resistor connected between the transistor base and a constant power supply. For now, I'll be assuming that on voltage for the base of the transistor is 0.6V meaning Ib = (Vp-0.6)/Rb.Knowing this, I can therefore replace the transistor for a current source where the current is equal to Beta*(Vp-0.6)/Rb. The problem for me now is finding the voltage equations at point Va and Vb. Could anybody enlighten me on how to do so? For Beta, I'll be using a quoted (from the datasheet for the BC337-40) value of 250.Thanks!

author: IanB
author_rank: Super Contributor
timestamp: April 23, 2015, 02:27:08 am
content: It's difficult to know how to answer when you present an abstract problem without a stated objective or application requirement.However, it is clear that VB = VA/2.It is also clear that VA = V+- R1 * IR1Furthermore it is clear that IR1= IR2+ IC(Q1)Can you explain where you are stuck?

author: pyrohaz
author_rank: Regular Contributor
timestamp: April 23, 2015, 02:30:21 am
content: Quote from: IanB on April 23, 2015, 02:27:08 amHi Ian,Thank you for your fast reply! If the transistor is operating in its active region, will there not be some current sharing happening between the potential divider and the transistor, meaning that Vb = Va/2 won't hold true?EDIT:Sorry, I didn't actually explain what I'm trying to figure out. I'm trying to find the TOn and TOff time dependency of a 555 timer by varying the amount of current sank from the control input. Va and Vb represent the upper and lower trip points (respectively).

author: IanB
author_rank: Super Contributor
timestamp: April 23, 2015, 02:43:27 am
content: Quote from: pyrohaz on April 23, 2015, 02:30:21 amVb is always equal to Va/2 because there is a potential divider with R2 = R3. Potential dividers divide potential differences regardless of what the potential difference happens to be.If you doubt this, try solving directly for Vb using Ohm's law.

author: pyrohaz
author_rank: Regular Contributor
timestamp: April 23, 2015, 02:57:15 am
content: Quote from: IanB on April 23, 2015, 02:43:27 amDoh! Of course! Well I feel stupid now...Vb = Va/2Va = (Vp - R1*Ic)/(1 + R1/(R2+R3))After calculating on paper then simulating, this is the equation! Thank you very much for clearing this one up for me.
relay basics - Page 1
Forum section: electronics / beginners

author: njkmonty
author_rank: Contributor
timestamp: May 03, 2018, 09:21:38 am
content: is ok to have a relay turn on other multiple relays? if so is there a rule about switching the ground or vc are there other unknown issues that a novice may be aware off?

author: Zero999
author_rank: Super Contributor
timestamp: May 03, 2018, 09:26:51 am
content: It makes no difference which side of the coil is switched. A reverse parallel diode should be used to protect the switching transistor.The question is too vague to give any more information than that.

author: njkmonty
author_rank: Contributor
timestamp: May 03, 2018, 09:35:39 am
content: is it ok to use a 5v spdt relay to switch on for example 5 x 5v dpdt relays?ive got one of these working (see below how ever i thought it would be easier to use the spdt relay to be able to switch on a seperate dpdt relay which i have plenty laying around.when i bought the relay module i thought it was dpdt

author: Zero999
author_rank: Super Contributor
timestamp: May 03, 2018, 01:19:57 pm
content: Quote from: njkmonty on May 03, 2018, 09:35:39 amIt would work, but isn't good design practise, which would be to but the correct DPDT module and keep that one for another project.I hope those relays aren't switching mains. It's unlikely those boards have sufficient creepage distances.

author: tpowell1830
author_rank: Frequent Contributor
timestamp: May 03, 2018, 06:10:08 pm
content: Quote from: njkmonty on May 03, 2018, 09:21:38 amSome relays have a built in diode and are polarized, check your relay diagram, usually on the relay box, to see if there is a diode shown.As for switching in the way that you describe, it depends on your application/use. If this is a one-off hobby project, I see no problem doing this. If this is an industrial application, I suggest checking with your local electrical authority/engineer for specifics. I have worked for companies as an electrician where the only requirements was results, and as long as there was no danger to humans or equipment, anything that would get the job done was allowed. However, some industrial environments, and I have worked these as well, have rules and guidelines in place.Hope this helps...
Relay coil diode placement question. - Page 1
Forum section: electronics / beginners

author: Chris Wilson
author_rank: Super Contributor
timestamp: January 21, 2014, 08:55:15 am
content: If I move a PCB mounted 12V coil relay off its PCB control board into another equipment cabinet, with the relay's coil powered from the external PCB still, do I NEED to move the diode across the coil with the relay, or can it now be remote, still on the control board? Thanks.

author: fcb
author_rank: Super Contributor
timestamp: January 21, 2014, 10:00:36 am
content: The back-emf diode is typically used in a circuit to protect the driver transistor, so it won't make any difference if you put it across the relay coil or on the driver circuit directly.It *might* matter if you placed it on a long spur however, but I can't think why anyone would do this.

author: Psi
author_rank: Super Contributor
timestamp: January 21, 2014, 10:06:39 am
content: Its good practice to keep it with the relay, you then know the high voltage is snubbed at that point and can never make it anywhere else.otherwise, if you had multiple connections and some wires were broken, or a plug wasn't connected, it might be possible to energize the relay with no diode present

author: Rerouter
author_rank: Super Contributor
timestamp: January 21, 2014, 10:07:08 am
content: Simplest answer is to mount the diode nice and close to the relay as it will shunt its switch on current through the diode thus keeping the current loop small,Paranoid answer is to mount a generic diode across the relay coil and a small capacitance across the switching device to limit any spikes due to long leads

author: Kremmen
author_rank: Super Contributor
timestamp: January 21, 2014, 10:22:53 am
content: Quote from: Psi on January 21, 2014, 10:06:39 amI agree the best place is right next to the relay coil. Mostly for making sure the diode is not inadvertently disconnected from the circuit. There won't be any "spike" as long as the diode is there; the diode provides a path for the coil current to smoothly ramp down to zero, dissipating into heat in the resistances present in the circuit. Only if the diode is absent will there be a voltage excursion due to the fact that coil voltage is proportional to the rate of change of current passing through it. Break the current == infinite change --> infinite voltage. At least in theory if not quite in practice.
relay coil voltage problem - Page 1
Forum section: electronics / beginners

author: SnakeBite
author_rank: Regular Contributor
timestamp: June 08, 2014, 07:46:41 pm
content: Hi,i designing an battery operated product that has voltage range of 11-14.4V and i'm using a 12v coil relay. in the datasheet says the min coil voltage is 9.6V and the maximum voltage is 13.2V. what is the simplest way to lower the voltage to the coil voltage range of the relay?here's the relay's datasheethttp://www.mouser.com/ds/2/307/ly_dsheet_gwj002-e2-10-48034.pdfi thought about using two diode in series but it's tricky to get exactly 1.2-1.4v voltage drop with 75mA.thanksIdo

author: retrolefty
author_rank: Super Contributor
timestamp: June 08, 2014, 07:52:45 pm
content: Well if you look up the coil current then you could calculate a series resistor that drops 1.2 vdc when the battery is at 14.4 vdc.

author: Fank1
author_rank: Regular Contributor
timestamp: June 08, 2014, 07:52:59 pm
content: Personally I would not worry about it, but just put a 16 ohm resistor in series with the coil.At 75 ma this will give you a 1.2 volt drop.

author: Andreas
author_rank: Super Contributor
timestamp: June 08, 2014, 08:26:33 pm
content: Hello,You are simply using the wrong relay.There exist other 12V relays with 9-16 or even 9-18V operating range.BTW. the upper voltage is usually for the upper operating temperature point.If you dont need the whole temperature range you can usually allow for higher coil voltages.With best regardsAndreas

author: SnakeBite
author_rank: Regular Contributor
timestamp: June 08, 2014, 08:40:00 pm
content: thanks guys

author: fcb
author_rank: Super Contributor
timestamp: June 08, 2014, 10:28:32 pm
content: I wouldn't sweat it, it's probably just spec'd at 13.2V to allow for indefinate on time at peak operating temperature. If you plan on running the coil for along time, look up 'coil economizer' circuits.
Relay contact ratings - Page 1
Forum section: electronics / beginners

author: nukie
author_rank: Frequent Contributor
timestamp: May 27, 2013, 03:06:21 am
content: Hi,I just bought an Omron MY2 DPDT relay to fix an equipment. From the window, the contact rating as follow..5A 240 VAC5A 28 VDCI don't understand why is there such a significant difference between AC and DC at the contacts?When I google, the explanation is that DC current requires higher contact rating than AC but why so?Is this because of the resistance difference between AC and DC?Vincent.

author: Rufus
author_rank: Super Contributor
timestamp: May 27, 2013, 03:22:06 am
content: Quote from: nukie on May 27, 2013, 03:06:21 amBecause an arc draw between the contacts as they open will extinguish on the next zero crossing of the ac current they are carrying. A dc arc can only be extinguished by the contacts moving far enough apart.

author: nukie
author_rank: Frequent Contributor
timestamp: May 28, 2013, 04:16:40 am
content: Great explanation, thanks!
Relay Footprint Question - Page 1
Forum section: electronics / beginners

author: ryanmills
author_rank: Unknown
timestamp: February 18, 2023, 12:46:28 am
content: Datasheet:https://www.te.com/commerce/DocumentDelivery/DDEController?Action=srchrtrv&DocNm=PE_bistable&DocType=Data+Sheet&DocLang=English&DocFormat=pdf&PartCntxt=9-1415389-1Part Number: PE014F02I used a latching relay (datasheet above) by mistake and I'm wondering if I can a find a non-latching relay that matches the footprint? Right now, I'm just going down the list for TE relays on digikey and not having any luck, seems they all have a slightly different footprints. Would anyone know an easier way to search for a relay by footprint?

author: fourtytwo42
author_rank: Super Contributor
timestamp: February 18, 2023, 09:30:23 am
content: Try this onehttps://docs.rs-online.com/d42b/0900766b81150885.pdf

author: Doctorandus_P
author_rank: Super Contributor
timestamp: February 20, 2023, 11:43:46 pm
content: The attached screenshot is one of the most atrocious things I've seen in a datasheet lately.The difference between placing pins on a 2.5mm grid or a 2.54mm grid is just big enough to cause problems when accumulated over such distance With 7 pitches it's 0.28mm.On top of that, Making it look like DIP-14 pin compatible but then putting pins 11, 12 and 14 in different locations is also not the smartest move. Also notice it's a bottom view, which is also annoying for designing a PCB Footprint.Somebody should go tho that shrek company and fire the guy responsible for that, or at least put funnels in his ears, paint his head green and parade him around for a week.

author: jfiresto
author_rank: Frequent Contributor
timestamp: February 21, 2023, 09:33:33 am
content: I think the 11, 12 and 14 are not pin numbers, but electrical signals numbers, to complete the A1 and A2.Could there be two versions of the relay, one with 2.5mm centers and the other with 0.1inch centers?The worst relay data sheet I recently had to deal with recommended a couple PCB drill holes that were too small, 1.0mm instead of 1.3mm. The manufacturer still had not corrected the error before they discontinued the relay, a pity as it had 10X the contact life of its competitors and its substitute.
relay holding current - Page 1
Forum section: electronics / beginners

author: LaserTazerPhaser
author_rank: Regular Contributor
timestamp: June 03, 2019, 10:53:49 pm
content: Datasheet does not depict any holding current. Whats the rule of thumb for these category of relays?http://www.hongfa.com:8080/pdfjs/web/viewer.html?file=/Uploads/PDF/HF102F_en.pdf&stamp=1559602009559

author: KMoffett
author_rank: Regular Contributor
timestamp: June 04, 2019, 12:34:16 am
content: Take a voltage a little higher than the "drop out voltage" and divide it by the coil resistance.Ken

author: rfengg
author_rank: Regular Contributor
timestamp: June 04, 2019, 12:49:46 am
content: Assuming that you are reducing the current to save on power, ~30% of the nominal operating current should be fine to "hold" the armature of the relay.30% reduction in the coil current, should give you ~1/10 power savings.The only downside to this is you cannot operate reliably in this condition if you are in a harsh environment with a lot of vibration and shock to the relay.Is the relay driven by a DC voltage or is there an option of PWM-ing it?The currents can be deduced from the voltages on the data sheet divided by the coil resistance.

author: LaserTazerPhaser
author_rank: Regular Contributor
timestamp: June 04, 2019, 04:10:08 am
content: Quote from: rfengg on June 04, 2019, 12:49:46 amGoing with this 40amp relayhttp://www.hongfa.com:8080/pdfjs/web/viewer.html?file=/Uploads/PDF/HF165FD-G_en.pdf&stamp=1559625739820instead as it handles more current. Its going to be powered by either a wall adapter or 12v battery pack series with a SPST series to relay coil since high current SPST switches are far more costly. Its going to switch a 18.5amp adapter into an inductive load

author: KMoffett
author_rank: Regular Contributor
timestamp: June 05, 2019, 01:46:08 pm
content: This might help:http://www.learningelectronics.net/circuits/reducing-relay-power-consumption.htmlYou would need to adjust voltages and component values for your project.ORhttps://www.instructables.com/id/Relays-DC-999-Less-Power-Latching-Option/Ken
relay module work unstable - Page 1
Forum section: electronics / beginners

author: markeev
author_rank: Newbie
timestamp: May 11, 2015, 06:58:03 am
content: I have purchased someMICRO USB Control 5V 4-Channel Relay Module.Sometimes it cannot ON or OFF the relay by click ON/OFF on RelayBoardManager.Must close application and run again.If connect to OMRON, will be more unstable.How to solve? Thanks!

author: con-f-use
author_rank: Unknown
timestamp: May 11, 2015, 12:38:31 pm
content: You will need to provide more details. There is a number of reasons this board might fail.- Cheap relays sometimes get stuck in one position (because some glue or sealant leaked or the contacts get fused together)- The USB communication might get out of sync and disconnect the board (from the price I assume it's using V-USB or similar which doesn't work perfectly)- There might be a bug in the software- Some channels might be overdriven and cause the micro to fail (too much current on a pin)- ...When the failiure happens check whether...-... the PC still recognized the USB device-... shaking the relays gets the relays unstuck (BE VERY CAREFULL NOT TO TUCH THE LIVE CONTACTS!)-... wrong relay contacts are fused together-... the build in serial is able to toggle the relays-... the fuse or chips get gets hot-...That's all I can think of on top of my head. Use your's now!BTW: While at the topic of relay boards, does anyone know if there is a chip similar to theULN2803(multi-channel darlington driver with fly-back diode) that is also opto-isolated and not too expensive?

author: TopLoser
author_rank: Unknown
timestamp: May 11, 2015, 04:47:33 pm
content: Are you switching inductive loads that are creating back-emf arcs that are crashing the micro on the board?

author: Rick Law
author_rank: Super Contributor
timestamp: May 15, 2015, 06:48:47 pm
content: Check your power level on the board. The relays requires quite a bit of power for the relay coil.I use same modelSonglerelays (on a different style board). Each relay requires 89.3mA (from data sheet, nornimal) to drive the coil. Add to that, you need some power to drive the other components. In real life measurement, it takes over 75mA to hold. I have not measured the pull-in current requirement.So, their 400mA specs has very little headroom. If you have something else connected to the same USB port/hub, your board may not have the needed power to drive/hold the relays.I can see there is a pin-header, check and see if it has V+ in. If so, you can external power it and see if the problem goes away.
Relay or transistor help - Page 1
Forum section: electronics / beginners

author: Crambone
author_rank: Frequent Contributor
timestamp: February 09, 2024, 04:05:55 pm
content: I’m looking for a device that will switch normal open to close when 8vdc 1mA is applied.Drew

author: Solder_Junkie
author_rank: Frequent Contributor
timestamp: February 09, 2024, 04:14:49 pm
content: Quote from: Crambone on February 09, 2024, 04:05:55 pma 2N7000SJ

author: themadhippy
author_rank: Super Contributor
timestamp: February 09, 2024, 04:52:16 pm
content: Does the switching side need to be isolated from the control side ? whats sort of voltage and current are you switching with your 8v 1ma?

author: Crambone
author_rank: Frequent Contributor
timestamp: February 09, 2024, 11:33:11 pm
content: It’s creating a short to key an amplifier.

author: Solder_Junkie
author_rank: Frequent Contributor
timestamp: February 10, 2024, 12:11:20 am
content: Quote from: Crambone on February 09, 2024, 11:33:11 pmA Kenwood transceiver? Try a 2N7000SJ

author: Crambone
author_rank: Frequent Contributor
timestamp: February 10, 2024, 01:37:21 am
content: I should have put more info I’m tapping into a 8vdc TX source and want to use that 8 volts to close an isolated normally open contact will go to a rca jack on the rear of the transmitter. I’m thinking a relay of some sort but not exactly what type since I only see 100mA on the 8vdc.The amp is a simple short to ground for operate. I just don’t want to be bothered using a foot switch.Not sure of one of these would work?https://www.mouser.com/c/electromechanical/relays-contactors-solenoids/low-signal-relays-pcb/?coil%20current=44.4%20mA~~64.4%20mA&coil%20type=Non-Latching&coil%20voltage=9%20VDC&instock=y&rp=electromechanical%2Frelays-contactors-solenoids%2Flow-signal-relays-pcb%7C~Coil%20Current%7C~Coil%20Type

author: themadhippy
author_rank: Super Contributor
timestamp: February 10, 2024, 01:57:14 am
content: QuoteHows about a 9v jobbie likehttps://www.farnell.com/datasheets/8046.pdfseems to kick in at 7.2V and only wants 16.7mA

author: David Hess
author_rank: Super Contributor
timestamp: February 12, 2024, 08:49:13 am
content: I would use an optocoupler like a 4N32/4N33 or TLP4597.
Relay pulse driver circuit. HP 11713A - Page 1
Forum section: electronics / beginners

author: Pezikon
author_rank: Newbie
timestamp: October 02, 2017, 07:49:41 am
content: Hello one and all,I have an Agilent 11713A switch driver that I’m using with Agilent 8765A coaxial relays. The 8765A is a single pole double throw relay. As it turns out the 8765A relay is ideally pulse driven. That is, it only requires a pulse of current to actuate the relay and it will stay in position without any more current flow. When it is driven with continuous current, it gets very hot. The 11713A switch driver only does continuous current. My question is, what circuit could I put in between the driver and the relay to get the desired pulse drive effect from an otherwise continuous current driver? I’ve got the switch wired up with a power supply and a breadboard so I can test out some ideas.This is essentially what the circuit looks like without any pulse driver circuit. The 11713A supplies the 24 volts which is always in contact with the relay. The 11713A completes the circuit for one of two paths (represented by the single pole double throw at the left) to energize a solenoid inside the relay and actuate the relay. The solenoids in the relay are represented by the two 200 ohm resistors.My intention is to put a circuit here, where the question mark box is at:This is what I have tried:When the Agilent driver completes the circuit, current will initially surge to charge the capacitor. This allows enough current to flow for the relay to actuate. The 1k-ohm resistor is there to discharge the capacitor when the Agilent driver breaks the circuit. When the circuit is complete though, the capacitor will fully charge and do nothing until it has a chance to discharge. Meanwhile, the 1k-ohm resistor acts as a current limiting resistor, reducing what would be 120mA to ~20mA.What’s undesirable about this solution is the current is never turned off, the 1k-ohm resistor limits the current but it’s still flowing. The 1-kohm resistor has to continuously dissipate 0.4W.The intention is use a circuit that doesn't require a separate power source. I humbly request any assistance.

author: Pezikon
author_rank: Newbie
timestamp: October 09, 2017, 07:38:29 am
content: In case anyone could use some help on this in the future...My next best attempt (showing only one 200 ohm solenoid):I still can't turn off the current flow, but it's down to 28mW across the 200ohm solenoid. The pulse is great; a solid 20ms of full current while the cap charges, followed by a steep roll off. Switching time spec for the relay is "15ms max", so 20ms is plenty. Disconnecting the circuit from ground allows the cap to discharge; but it can only discharge through the 680k-ohm resistor so it takes a second or two... meaning I need to be careful to not switch back and forth faster than that.
Relay question - Page 1
Forum section: electronics / beginners

author: RyanG
author_rank: Regular Contributor
timestamp: June 15, 2017, 03:43:37 am
content: We have some relays that we use to start motors at work. I don't actually know which wire on the relay is what. I also don't fully understand how the relay works. I get what it does, but not the way it does it.The relay:https://www.grainger.com/product/GRAINGER-APPROVED-Potential-Relay-5MLY9The internal wiring diagram is attached. I don't know which would be the "hot" connection. Contacts 4 and 6 are not used in our application.

author: Mr.B
author_rank: Unknown
timestamp: June 15, 2017, 03:54:54 am
content: It is a Potential Starting Relay used in motor starting applications where you have a start winding and a run winding.Theory here:http://www.achrnews.com/articles/93735-potential-starting-relays
Relay rating - Page 1
Forum section: electronics / beginners

author: AxleD
author_rank: Regular Contributor
timestamp: April 04, 2015, 08:30:12 am
content: Hi All,Just need some clarity on the DC current switching capability of a relay. The relay part # is HF115F and i have included some of the specs from the datasheet (not sure if i could post the whole datasheet).1. There is no reference to DC current handling capability. Can this relay safely handle 1.5A DC at 30V?2. What does the contact resistance (1A 6VDC) refer to?Thanks for the assistance.

author: Zero999
author_rank: Super Contributor
timestamp: April 04, 2015, 09:11:31 am
content: 1) Of course, if it can switch 8A at 300VDC then 1.5A at 30VDC will be no problem.2) That's just the test conditions for measuring the contact resistance which is no more than 100mA @ 1A & 6V.

author: Psi
author_rank: Super Contributor
timestamp: April 04, 2015, 09:26:41 am
content: It really depends what DC load you are switching.If the load is purely resistive and steady (no inrush current) then you can switch 8A no problem.If there's lots of inrush current derating as low as 20% is sometimes needed to get good lifespan. Typical inrush current from say a lamp can be 10 times higher than the steady current.If the load is highly inductive then you will get a lot of arcing when the relay breaks contact and this will slowly damage the contact surface. 50% is a good rule of thumb.If switching a motor a 40% derating is advisable.Since your relay is 8A rated and you only need 1.5A you are covered for all options.

author: AxleD
author_rank: Regular Contributor
timestamp: April 05, 2015, 12:17:36 pm
content: Thank you both!

author: bktemp
author_rank: Super Contributor
timestamp: April 05, 2015, 03:24:27 pm
content: Quote from: Hero999 on April 04, 2015, 09:11:31 amIt can switch 300V DC or it can switch 8A, but not 8A at 300V.On the last page of the datasheet there is a nice curve showing the maximum switching power depending on voltage and current for both AC and DC conditions.30V 1.5V is possible, but close to the limit. If you have an inductive load I would not use this relais.

author: Zero999
author_rank: Super Contributor
timestamp: April 05, 2015, 03:36:50 pm
content: Quote from: bktemp on April 05, 2015, 03:24:27 pmThat makes sense but it would've been nice if the full datasheet was posted, rather than a tiny extract from it.
Relay ratings - Page 1
Forum section: electronics / beginners

author: kr15_uk
author_rank: Newbie
timestamp: July 21, 2016, 12:06:12 pm
content: Ladies and gents,I've bought couple of relays from the eBay and they are rated DC 30V/10A but I'm planning to use it with 12V. Is there a way to figure out how much it can handle AMP on 12V?!Probably I'm wrong (that's why I'm asking) but my only logical conclusion was to figure out the hardware resistance - 30V/10A = 3ohm, 3ohm/12V = 4AAm I on the right track or just talking rubbish?!Thanks.Regards,Kris M

author: Brumby
author_rank: Unknown
timestamp: July 21, 2016, 12:13:08 pm
content: Ohms law does not apply to the contact rating.At 12V DC, you can run that relay up to the stated limit of 10A.

author: StuUK
author_rank: Frequent Contributor
timestamp: July 21, 2016, 12:19:02 pm
content: Quote from: Brumby on July 21, 2016, 12:13:08 pmShouldbe able to! depends whether they are cheap rubbish that don't meet their specification....

author: dmills
author_rank: Super Contributor
timestamp: July 21, 2016, 12:20:32 pm
content: Not the way it works, the two numbers (30V, 10A) are maximums, there may also sometimes be a power or VA product limit.You can run the thing at up to 30V and up to 10A, so maximum current at 12V is 10A, just the same as the 30V case.You might sometimes see (30V, 10A, 100w) in which case all three limits apply, at less then 10V, the limit is 10A, at less then 3.33A the limit is 30V, and between the two you have a straight line that respects the power limitInterestingly you will often find relays rated for far more voltage in AC service then DC, this is because an AC arc will tend to quench when the current goes thru zero due to the AC supply, where a DC arc can last.AC relays also have different ratings depending on the load, usually highest for resistive loads, and very much lower for inductive, tungsten lamps, florescent lighting or motor loads.Regards, Dan.

author: Brumby
author_rank: Unknown
timestamp: July 21, 2016, 01:34:34 pm
content: Quote from: StuUK on July 21, 2016, 12:19:02 pmAbsolutely not.QuoteThat's only applicable if the ratings given were bullshit in the first place and/or construction was inadequate.Read whatdmillsposted.
Relay specifications - Page 1
Forum section: electronics / beginners

author: Tantalum
author_rank: Regular Contributor
timestamp: June 26, 2020, 06:54:39 am
content: HelloI have 3 questions about a relay.Q1:I needed a power relay for high DC (24V, 16A max) and on mouser I found the HE-S series from Panasonic.But it's not really clear if it is really safe to use them with DC current. In the datasheet there are some DC specs but not as detailed as for AC.I would say it's ok for DC usage (according to the last graphic), but I prefer somebody to confirm.Q2:On the 3rd image, there are specs for inductive load, but only for AC current, nothing for DC current. What about the max DC current for inductive load???Q3:On the second image there are the contact resistance specifications.First I find the data inaccurate 3...100mOhm. Strange not?And what do they mean with(by voltage drop 6V DC 20A)?Thank you

author: Vovk_Z
author_rank: Super Contributor
timestamp: June 26, 2020, 08:57:51 am
content: Q1: A1: from Max switching capasity figure it is capable to commutate 24V DC 16A, active load.Q2: A2: of cause it highly depends on inductivilty. The worst case the switching capability decreases in up to about ten times. So it will withstand only about 3 A of highly inductive current at 24VDC (I may wrong, but +- so).Q3: A3: don't know that contact science but contact resistance depends (nonlinear) on commutating current value (because of arcs/sparcs etc).

author: Tantalum
author_rank: Regular Contributor
timestamp: June 26, 2020, 02:05:05 pm
content: Thank you very much for your answersQuote from: Vovk_Z on June 26, 2020, 08:57:51 amWould a snubber solve the issue?(Well actually, there won't be big engines on the circuit. Only some (solenoid) electromechanical valves)

author: TimFox
author_rank: Super Contributor
timestamp: June 26, 2020, 02:14:37 pm
content: That snubber network has problems with AC, since it passes some current with the contact open, but should work for DC.However, it is usual with inductive loads to include a diode across the inductor (reverse biased when voltage applied to the load) to catch the inductive kickback when the current is interrupted.

author: Vovk_Z
author_rank: Super Contributor
timestamp: June 26, 2020, 08:10:20 pm
content: Snubber helps a lot of cause but not 100%. It can be used in parrallel with a load first, so eliminates a need to put it parallel to relay contacts. And of cause it may be two snubbers - "main" one across an inductive load and second one (with lesser/smaller capacitor) across relay contacts.Snubber helps to increase significally relay contacts life but first relay have be capable to. I mean if relay contacts are not rated for some load then it is very hard to change it significally with a snubber. (Otherwise a snubber must be about a size of a load).
Help with relay support components - Page 1
Forum section: electronics / beginners

author: TWilson
author_rank: Newbie
timestamp: December 31, 2016, 11:50:09 am
content: I am trying to build a relay circuit. It is DPDT.One relay contact on NC is connected to a battery, through a NO momentary switch which goes through the relay coil. This is just for initial mains free triggering.The second relay contact on NO is connected to mains which runs a switch mode power supply to power the relay and run a motor.I have an issue where I don't know if I need a flyback diode as well as a short delay capacitor across the relay coil. The capacitor is there to keep the relay open just long enough to allow the switch mode power supply to energise and provide current to keep the relay open. A momentary NC switch between the power supply and the relay is used to disconnect the relay and shut down the circuit. The motor bleeds off any excess power remaining in the power supply otherwise the relay gets reactivated.I have also had issues where the circuit seems to get stuck open despite all power to the relay coil being completely disconnected.Relay is a 5v coil with mains rating (240V) on the switches at 250mA.Power supply uses 240V 5mA.There is a 1N4007 diode reversed across relay.Capacitor is 470uF electrolytic diode.

author: Simon
author_rank: Unknown
timestamp: December 31, 2016, 12:08:21 pm
content: always use a diode unless it interferes with your circuit.

author: tpowell1830
author_rank: Frequent Contributor
timestamp: December 31, 2016, 03:24:45 pm
content: You should include a schematic, even if you sketch on a napkin and take picture. Then the text will explain what you're after.PEACE===>T
relay's pcb question - Page 1
Forum section: electronics / beginners

author: Karamel
author_rank: Regular Contributor
timestamp: October 28, 2015, 01:26:12 am
content: Hi,A few times ago, I have seen this relay boardhttp://tr.aliexpress.com/item/free-of-charge4-road-5-v-10A-optical-coupling-isolation-relay-module/32304609560.html?adminSeq=206174137&shopNumber=343255in aliexpress store. I am wondering that, why did they dig around relay's common pin with drill?Is it useful or superstitious belief? Which one is it?

author: Paul Moir
author_rank: Frequent Contributor
timestamp: October 28, 2015, 06:09:31 am
content: It's to further isolate the common pin from the coil pins adjacent to it, and the other PCB traces below them. They're called "isolation slots" for that reason.If the PCB gets contaminated with dust or dirt, the PCB can become slightly conductive which can help initiate an arc to the isolated side. The slot helps prevent this. The term for this is 'creepage' such as, "The isolation slot increases the creepage distance."For more information, google "creepage and clearance".

author: Ian.M
author_rank: Super Contributor
timestamp: October 28, 2015, 08:04:48 am
content: Unfortunately the slots in the above photo don't extentd far enough to significantly increase the creapage distance between the coil pin pads and the tracks to the common contacts. Ideally they'd be long enough so that the shortest distance along the board surface round the end of the slot was the same as the distance between those pins of the bare relay. There is no point in making the distance greater than that due to the creepage distance across the relay base.

author: crispy_tofu
author_rank: Super Contributor
timestamp: October 28, 2015, 09:59:58 am
content: Related:https://www.eevblog.com/forum/projects/pcb-slotscutouts-when/?topicseen

author: ez24
author_rank: Super Contributor
timestamp: October 28, 2015, 10:25:55 pm
content: Quote from: crispy_tofu on October 28, 2015, 09:59:58 amHad crispy tofu for lunch today

author: crispy_tofu
author_rank: Super Contributor
timestamp: October 28, 2015, 10:39:48 pm
content: Quote from: ez24 on October 28, 2015, 10:25:55 pmI will avenge my brethren.