Equivalent components - Page 1
Forum section: electronics / beginners

author: Savetheday
author_rank: Regular Contributor
timestamp: November 20, 2016, 01:00:28 am
content: HiI have a very common question. How do you choose equivalent components? What facts and points have to be considered? Are there any equivalent list or website or something like that? Ok. I know for some IC's we could choose same end numbers.for example 555 timer LM555 or NE555 etcbutI need a ICL7107CPL1https://www.google.de/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&uact=8&ved=0ahUKEwj3vfqFjrbQAhVFKcAKHaZ4B2EQFggjMAE&url=http%3A%2F%2Fwww.intersil.com%2Fcontent%2Fdam%2FIntersil%2Fdocuments%2Ficl7%2Ficl7106-07-07s.pdf&usg=AFQjCNHxERnga14dj4SjaYRiHy8OooKCeA&sig2=nMxs-YVJKgAFsImpqbTH8A&bvm=bv.139250283,d.ZGg(Digit, LCD/LED Display, A/D Converter)but I found in local store ICL7117RCPLhttps://datasheets.maximintegrated.com/en/ds/ICL7116-ICL7117.pdfThere are some small differences.Should I use instead of that one?Thanks.

author: Ysjoelfir
author_rank: Frequent Contributor
timestamp: November 22, 2016, 11:27:54 am
content: Your question can`t be answered that easily since the possibility to replace one part with another is always dependant on the circuit you intend to use the part in.As for the equivalent lists: I have some books pointing out equivalent components, but those are quite old. I would guess that there are also more modern ways to find equivalent parts online, but personally I don`t know about those, since I realised quite early that the above stated is the way to go - analyze your circuit and judge by yourself what specifications you need for your part and search for one at the known manufacturers websites or your favorised part vendor.

author: Savetheday
author_rank: Regular Contributor
timestamp: November 24, 2016, 03:54:46 pm
content: I see.I would like to give a try some of pcb schematics that I already found in online but most of the time I screw up in the middle of the project.Because of some component are not available in local shops or something I try didn't work. I know you may order every components online.But I don't like that way.And some of the time I have already have equivalent one in my toolbox.This is the project I'm working on.http://members.shaw.ca/swstuff/esrmeter.htmlWhat about small passive components like 2N2222 NPN transistorhttp://www.farnell.com/datasheets/296640.pdfHow do you do if there are not avalible at local shops?Could we use instead of 2N3904https://www.sparkfun.com/datasheets/Components/2N3904.pdfthanks a lot.

author: IonizedGears
author_rank: Regular Contributor
timestamp: November 24, 2016, 04:29:17 pm
content: If you want to replace a component with another there are a few things you need to check:Are the pinouts the same?Are the power dissipation capabilities the same?Is this replacement as fast as the original?...Basically the specific characteristics between the replacement and the original which you can find by comparing the datasheets.Then you need to see the specific requirements of the circuit.Is the circuit component-critical--If the circuit was designed with specific component characteristics in mind (Hfe/speed for a transistor, ESR for a capacitor, etc.)?This part requires some circuit analysis.Sure you may be able to find specific replacement guides online, but you should try to learn how to compare these things. You'll be better for it.Lets take your latest question on the 2N2222 vs 2N3904.Note: Both of these are considered to be jellybean components due to the abundance and cheapness. They are interchangeable in most cases.Both have the common EBC pinout.Both have 625mW power dissipation (You won't want to actually run them to this point w/o a heatsink, but at that point you would move to power transistors)The main difference is in the collector current.The 2222 is rated for 1A Ic while the 3904 is rated for 200mA Ic. Generally you don't want to reach these limits for long term reliability so I would bring that down to about 500mA Ic for the 2222 and 100mA on the 3904. At this point you might wonder how they could have the same power dissipation capabilities if their rated collector currents are so different but remember that power = I^2R. Where R is essentially the resistance between the collector and the emitter which relies on the conduction angle (no need to actually know what this is now, just know that if Power=I^2R), then power is at it's minimum when resistance is very high so no current flows, or resistance is very low, where a lot of current flows but based on R being very low, power dissipation is pretty low compared to when the transistor is "half-on" where the maximum power dissipation occurs. So power dissipation is based on more factors than just rated current handling. You might have already known this, but I like explaining things and it tied in with the topicAlso, if they aren't available at local shops, just buy them off of Ebay, Mouser, Digikey, etc. Shipping can be high so people like to make large orders at a time to save on shipping from single suppliers like Mouser or Digikey.

author: Cliff Matthews
author_rank: Unknown
timestamp: November 24, 2016, 06:19:33 pm
content: Check transistor replacements athttp://alltransistors.com/and the 2N2222 is an active component, see:http://www.allaboutcircuits.com/textbook/semiconductors/chpt-1/active-versus-passive-devices/

author: Audioguru
author_rank: Super Contributor
timestamp: November 24, 2016, 07:30:22 pm
content: You are planning to make a very old circuit that uses an old LED display that eats batteries. For many years a multimeter has used an LCD display that uses very low power so its battery lasts a long time.The circuit for a modern multimeter also shuts it off if it is not being used.

author: Savetheday
author_rank: Regular Contributor
timestamp: November 25, 2016, 05:24:36 pm
content: Quote from: IonizedGears on November 24, 2016, 04:29:17 pmGreat explanation.I must first internalize it.Quote from: Cliff Matthews on November 24, 2016, 06:19:33 pmI`m looking that website I think its going to be useful.Quote from: Cliff Matthews on November 24, 2016, 06:19:33 pmSorry It was a active component.I said wrong.Quote from: Audioguru on November 24, 2016, 07:30:22 pmOk. I am not going to build that LCD display meter because of some components that I couldn`t find so I changed that project.There are so many different type of esr meters.Its going to be analog one.There will be no batteries needed I'm going to use my self made power supply.One other Issuecould we use 0.47uF 275V instead of 0.47uF 400v ?This is the last state of my project but it's still dont workThanks.

author: Seekonk
author_rank: Super Contributor
timestamp: November 25, 2016, 05:52:11 pm
content: could we use 0.47uF 275V instead of 0.47uF 400v ?Yes, if it is a X2 capacitor. It will say X2 and have lots of approvals printed on it. You should always use a X2 line rated capacitor on line voltage because you never know hoe that other capacitor has been built

author: Savetheday
author_rank: Regular Contributor
timestamp: November 26, 2016, 01:41:46 am
content: I have found in my toolbox BC338http://alltransistors.com/transistor.php?transistor=22966http://www.mouser.com/ds/2/149/BC337-193546.pdfBoth (BC338 and 2N222) NPN transistors have same (Forward current transfer ratio) hFE (min 100). However, it didn't work.and only remarkable difference is frequencyBC338 2N2222Transition frequency (ft), MHz: 60 ----- Transition frequency (ft), MHz: 250I am guessing, I need above or exactly 100 MHz?By the way Im learning new stuffThanks all.

author: IonizedGears
author_rank: Regular Contributor
timestamp: November 26, 2016, 02:17:41 am
content: Could be related to it being a epitaxial transistor, don't know to much about the restrictions with that type of transistor. Did you make sure that you put it in correctly? A quick lookup of the data sheet shows that the pinout of the BC338 is CBE instead of the conventional EBC.

author: Savetheday
author_rank: Regular Contributor
timestamp: November 26, 2016, 09:49:01 pm
content: Quote from: IonizedGears on November 26, 2016, 02:17:41 amI don't know that doesn't change anything either. I also used Zener Diode 1N914 instead of 1N4148. I think both are the same.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: November 26, 2016, 10:45:26 pm
content: I don't know what instruments you have available to check/verify what is working or not. The Zener diode will probably work in place of the 1N4148.Is your transistor good? Use a multimeter to check BE, BC and CE continuity. Should look open CE and like a diode for the other two. If your meter includes an HFE function use it to verify the transistor still works like a transistor.Start at the beginning of the circuit and verify that everything is working before the transistor. Do you have an AC voltage at the output of the first stage. If you have an oscilloscope or frequency meter check to see if it is near 156 kHz. Then check for an AC voltage across the test pins. And so on.

author: vk6zgo
author_rank: Super Contributor
timestamp: November 27, 2016, 12:00:00 am
content: (1) The 1N914 isnota zener-----it is a small signal diode with virtually identical characteristics to the 1N4148.(2) The only zener in the circuit is D7 which is used for the 5v supply.(3)The thing is only running at 156kHz,soft won't come into it.(4) In a Common Emitter stage with an unbypassed Emitter resistor,the Gain (A) is (within limits) pretty much independent of transistor characteristics,& is determined by the values of Rc & Re,so in this case,A= R11/R12,which should give a gain of about 22 (the original schematic says 10.5---go figure!)The 2n3904,or BC338 should work OK,as should a BC107,BC108,BC547,BC548,or even most small signal NPN transistors you might salvage fom an old PCB.After checking your transistor looks "like a diode" for each of the two junctions,you then have to determine which leads are the Collector & Emitter.Even if your meter doesn't have a HFE function,you can still check this,as well as whether the thing has gain.Using your DMM in the "diode check" mode,connect the two device leads which you need to identify to the RED & BLACK DMM test leads.Now comes the disgusting part:-Spit on your finger and touch both the base & the transistor connection which is connected to the RED DMM test lead.The DMM will give a reading.----write it down.Swap the Test lead connections & repeat the test--again the DMM will give a reading.Compare the two readings----thehigher(No! it's the lower one--higher current,lower reading)one shows which is the correct connection.For an NPN device,the Collector will be the lead connected to the DMM RED test lead.To check a PNP device,the polarities are simply reversed.You have also learnt something--- transistors will work backwards,even if not very well!The voltage rating of C5 basically depends upon what sort of circuitry you are likely to be testing.You won't be testing active circuits,so all you normally need is a DC rated device,just in case the caps are still charged.I think the original guy used an old 400v Poly ester cap because that was what was in his junkbox.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: November 27, 2016, 06:01:58 am
content: Quote from: Savetheday on November 24, 2016, 03:54:46 pmA transistor is an active device.

author: Savetheday
author_rank: Regular Contributor
timestamp: November 28, 2016, 08:09:40 pm
content: Quote from: vk6zgo on November 27, 2016, 12:00:00 amI thought they were zener but fact they are "Small Signal Fast Switching Diodes"Quote from: vk6zgo on November 27, 2016, 12:00:00 amR12=210 2k2/210~=10I have some more of them (BC338 transistors) I thing they are in good condition.I have tried with R12=210 ohms that doesnt do anything. Im waiting for the scale needle to move back and forth but that moves only when I measure with DMM resistance.And it shows something like 3.2Mohms it moves all the way end.Quote from: vk6zgo on November 27, 2016, 12:00:00 amI think Its getting more complicated.Im going to use only usual way.I would like to stay in beginner mode.I use most of the case Datasheet.And for BC338 1-Collector 2-Base 3-Emitterbut I measureBase(Red test lead)-Collector (Black test lead) 0.661 VBase(Red test lead)-Emitter (Black test lead) 0.662 V there is no big differences.Quote from: vk6zgo on November 27, 2016, 12:00:00 amthat's great then I don't need anything else.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: November 28, 2016, 10:27:48 pm
content: Your transistor appears to be functional, with adequate if not exciting gain. Is there a reason you are focused on the transistor? The schematic suggests other tests you can run with the multimeter you have to verify that things are working as they should up to the transistor stage?Do you have 5V at the top end of R3 and R11 and at pin 14 of IC1?Do you see 250 mV of AC at TP1? With your first meter you should be able to measure the frequency which should be about 156 kHz. Is it? If you don't see this check pins 4, 6, 8, 10 and 12 of the 74HC14 where there should be about 4 V pp AC at the 156 kHz. If those readings are correct check values for R2 through R7 and capacitor C4 and double check that power and ground to the IC are connected.Do you see 180 mV of AC at the positive side of C2 with TP1 and TP2 shorted? Does it go to zero when you open the connection between TP1 and TP2?As a final thought. I don't know what kind of meter you are using for this circuit. It will not in general work with a DMM substituted for the analog meter specified.Troubleshooting a non-working circuit requires a careful process of elimination. Follow the signal from the point of generation to point of use, and establish to the best of your ability whether each stage is working. In this case a frequency is generated in section D of IC1 (pins 1 and 2). If you can establish that that is working follow the result forward. The remaining sections are used to increase the available power and isolate the frequency generation from anything that happens in the later stages. Again, simple checks will tell if this is working. Keep at it until you find something that doesn't seem right. Then try to figure out what could cause the problem.

author: Savetheday
author_rank: Regular Contributor
timestamp: November 29, 2016, 10:22:50 am
content: Quote from: CatalinaWOW on November 28, 2016, 10:27:48 pmR11 top:5.04V DCR11 down:3.578V DCR3 left:1.251V DCR3 right:85.9mV DCIC1Pin1:4.270V DC Pin14:5.04V DCPin2:1.550V DC Pin13:1.553V DCPin3:1.551V DC Pin12:1.268V DCPin4:1.277V DC Pin11:1.552V DCPin5:1.551V DC Pin10:1.261V DCPin6:1.270V DC Pin9:1.553V DCPin7:Ground Pin8:1.256V DCThere is no AC VoltsBy the way I use 5 volt DC powersupply.Quote from: CatalinaWOW on November 28, 2016, 10:27:48 pmThere is no AC volt 0.001 0.003 V Both test leads TP1 TP249.78 HzQuote from: CatalinaWOW on November 28, 2016, 10:27:48 pmI see only Black DMM Lead connected to powersupply ground connection and Red DMM lead open circuit.(no connection) 1.328V AC. Nothing more.Thanks.

author: vk6zgo
author_rank: Super Contributor
timestamp: November 29, 2016, 03:21:41 pm
content: Quote from: Savetheday on November 28, 2016, 08:09:40 pmThe original schematic for the page you linked to shows R12 as 100QuoteIt's not really at all complicated if you remember that Bi-Junction Transistors (BJTs) need to be "biased on" before current can flow between Emitter & Collector.You are probably correct in your conclusion on which element is which,but this will be a good check.Now,instead of looking for diodes between base & the other pins,place the DMM red lead on the transistor pin you have identified as the Collector,& the black lead on the Emitter.Your DMM will read something along the lines of OL.(or Infinity)Now,touch the Collector & Base simultaneously with a damp finger.The finger looks like a resistor between the Collector & the Base,so the Base will be positively biased ,& the DMM reading will drop to a real lower reading.Write it down,& try the connections the other way round,with red on the Emitter,& black on the Collector---again the DMM will read OL.Use your finger to connect the Emitter to the Base.If your identification was correct,you will again see a real reading on your DMM.but it will be a much higher one.Note! I stuffed up this test in my earlier posting --you will see an edit if you revisit itRe: The 156KHz oscillator:This should produce a pretty good square wave,so it will hopefully have odd harmonics out to the 5th one.As luck would have it,this 5th harmonic,at 780kHz,falls within the "Medium Wave Broadcast Band".If you have a radio with this band on it,place the radio & device close together & tune across the band.If the oscillator is working,you should hear averystrong unmodulated signal at 780kHz (or near as dammit).

author: WaveyDipole
author_rank: Frequent Contributor
timestamp: November 29, 2016, 04:16:05 pm
content: Just to answer OPs question regarding the ICL7107CPL1 and ICL7117RCPL, comparison of the spec sheets would seem to illustrate the first couple of answers. The chips do appear to befunctionallycomparable and both appear to be in a 40pin PDIP package, however the 7117 has an additional 'HOLD' pin and a close comparison of the layout in both spec sheets indicates that some pin assignments have been changed to accommodate this. Therefore the 7117 could not just be used as a 'drop-in' replacement. Thought would need to be given to the new pin layout of the chip so that it is wired correctly, to whether the HOLD pin might be taken advantage of or whether it should be ignored (in which case should it be grounded or n/c), and how to work around the missing CREF- pin should it happen to be used by the existing circuit. So in this case, it is not a straightforward swap although with careful consideration and some modification of the circuit itmightbe possible to use it.As a general guideline, the determination is made by careful comparison of the original part specification with the specification sheet of the substitute part under consideration to ensure that its operating parameters comfortably meet the requirements of the circuit. The operating parameters will vary depending on the type of component. Substitution will usually require some understanding of the characteristics of the component and their relative importance, and also of the circuit itself - what it is designed to do and how it works. There is no 'one size fits all' shortcut answer. It comes with time and experience but as you have already seen from the replies so far, forum members will usually be happy to help.

author: suicidaleggroll
author_rank: Super Contributor
timestamp: November 29, 2016, 04:31:04 pm
content: To touch on the original question and what some other posters have mentioned, in order to identify a suitable replacement component you need to know why the original was chosen. Op-amps are a good example, because the package and pinouts are pretty much standard, but even then there are so many different parameters you can focus on that matter in different applications. In one application you might care about offset voltage and drift, in another maybe it's input bias current, or bandwidth, or drive current, or quiescent current, or rail-to-rail input or output, or some combination of these, or maybe none of them really matter and all you care about is cost. Without knowing why the original part was chosen, you can't make an educated decision on a suitable replacement.Lately I've gotten in the habit of making notes on my component selection when designing a board. For each component I just make a quick note of why it was chosen - which aspects matter in the design, where the thresholds are, etc., so that if/when it goes obsolete I can quickly  identify a suitable replacement without having to re-analyze the circuit.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: November 29, 2016, 06:48:58 pm
content: Quote from: Savetheday on November 29, 2016, 10:22:50 amI misread the schematic. 5VDC should not appear at R3, but at R9. But your other measurements adequately confirm that 5V is getting to the circuit properly. The fact that you are not getting the appropriate AC voltages and that the frequency is typical of line noise pickup indicates the oscillator is probably not working. You may have a bad 74HC14, or there may be other problems (solder bridge, bad resistance value, etc.). You will need to poke around that section of the circuit and get it working before you know if you are having problems with your transistor.

author: Savetheday
author_rank: Regular Contributor
timestamp: December 01, 2016, 10:29:16 am
content: Quote from: vk6zgo on November 29, 2016, 03:21:41 pmSorry I couldn't answer you guys earlier. I'm working in my garage and it's cold out hereI know I have just tried.But that doesn't work. I puted 100 ohms backQuote from: vk6zgo on November 29, 2016, 03:21:41 pmI did it with my DMM resistance mode I'm not sure ??collector red lead and emitter black lead 6.50Mohms andemitter red lead and collector black lead 11.40MohmsQuote from: suicidaleggroll on November 29, 2016, 04:31:04 pmQuote from: WaveyDipole on November 29, 2016, 04:16:05 pmOne of my old esr project I think that was second one I have to buy 2 layers Pcbs although I tried 4 or 5 times but couldn't etch my self pcb so I decided to buy 5 etched pcbs. My project was resulted with success.But there were 4 more pcbs and I thought I could give them a way to my friends with available Ics components and whatsoever.but I'm going to get back to that project in future.

author: vk6zgo
author_rank: Super Contributor
timestamp: December 01, 2016, 03:50:34 pm
content: Quote from: Savetheday on December 01, 2016, 10:29:16 amNo,you don't use the resistance mode---DMMs are designed to not turn on diode or transistor junctions in that mode.You have to use Diode Test mode.Anyway,save that test as a "fun" thing to try later,as your measurements in reply number(16)Quoteseem to indicate that the transistor is turned on & Collector current is flowing.Lack of drive from the oscillator circuit is,as others have said,the more likely problem.Have you tried listening for the 5th harmonic with an AM radio as I suggested?