Breadboard power supply? - Page 1
Forum section: electronics / beginners

author: YurkshireLad
author_rank: Frequent Contributor
timestamp: February 15, 2021, 04:33:04 pm
content: Hi all, complete beginner here.I have an Elego (Elegoo?) breadboard power supply that came with their Arduino starter kit. I tried to use the breadboard power supply to power the DHT11 humidity/temperature sensor at 5V, but it wouldn't work. I did some research and found some posts stating that some breadboard power supplies can supply more than 5V when configured for 5V instead of 3V. So I used my multimeter and on two different days, I got readings of 4.96V and then >7V, when my breadboard was configured for 5V.I noticed on these forums that someone recommended this breadboard PS -https://components101.com/modules/5v-mb102-breadboard-power-supply-module. Its design may be slightly different than mine, so perhaps there is a difference in manufacturing quality as well as the stability of the 5V output?Would you all still recommend this MB102 breadboard PS or is there an alternative that I could use? I don't need a bench power supply, just something to power one or more breadboards so I can prototype.Many thanks

author: bob91343
author_rank: Super Contributor
timestamp: February 15, 2021, 07:14:24 pm
content: Consider a 9V battery supplying a 7805 regulator.

author: Peabody
author_rank: Super Contributor
timestamp: February 15, 2021, 08:45:52 pm
content: I have several of this type of power supply, and find them to be very convenient. But two of mine have died - the voltage coming out of one of the regulators is too high. So you have to test the voltage each time you use it to make sure the voltage is right. I don't know if there's any difference in the various sources of these devices. Mine are branded YwRobot MB V2 545043.

author: mvs
author_rank: Frequent Contributor
timestamp: February 15, 2021, 10:17:29 pm
content: 1117 LDOs can oscillate without proper decoupling caps and MB102 design does not stick to datasheet recomendations.If you buy MB102, i would recomend you to feed both rails to breadboard and connect some >47µF electrolytic cap to each one.

author: tooki
author_rank: Super Contributor
timestamp: February 15, 2021, 10:38:29 pm
content: Quote from: bob91343 on February 15, 2021, 07:14:24 pmOr just a 3xAA battery holder, fitted with alkaline cells. New cells start at over 1.7V, so more than 5V, and will produce 4.5V over most of their useful life, which most circuits are happy with. (The Arduino Uno's MCU expressly supports lower voltages, and the Mega will work fine, even if it's unofficial.)

author: RoGeorge
author_rank: Super Contributor
timestamp: February 15, 2021, 10:52:13 pm
content: Quote from: YurkshireLad on February 15, 2021, 04:33:04 pmWhy don't you power the sensor from the Arduino board voltages?This is how it is done usually. Arduino has both 5V and 3V3 outputs, and the DHT11 sensor is very low power, so it is safe to power the sensor straight from the Arduino board.

author: YurkshireLad
author_rank: Frequent Contributor
timestamp: February 15, 2021, 10:59:49 pm
content: Quote from: bob91343 on February 15, 2021, 07:14:24 pmThanks all. Learning to use a 7805 regulator would make an interesting little project. I'll look into this and perhaps I can make my own little board that is powered by a 9V wall wart, and provides 3.3V or 5V. Something to work towards.I am using the Arduino to power any sensors that need 5V, but I've sort of moved on from the Arduino to ESP8266s and ESP32s, so the Arduino is otherwise redundant.I could use batteries for sure, but I'd prefer to stick to mains supply, so I don't have to replace the batteries.Thanks again for the interesting replies.

author: nightfire
author_rank: Frequent Contributor
timestamp: February 15, 2021, 11:01:59 pm
content: I also have received a similar power supply with a cheap starter kit, and one of the voltage regulators went south after a few minutes...Seems to be cheap build quality (or being propagated for higher supply voltages than it would be good for them- mine was rated vor 12VDC)

author: bobbydazzler
author_rank: Regular Contributor
timestamp: February 16, 2021, 02:57:44 pm
content: Seeing this thread title triggered me into retrying mine, within a few seconds of pluging in the dc plug(I forgot it was a 26v plug) the 10uf eloctrolitic cap blew up in my face. Luckily the debris didn't hit me or anything so yeah a 26v dc wallwart is too much for this supply.

author: tooki
author_rank: Super Contributor
timestamp: February 16, 2021, 08:25:24 pm
content: On my unit, that cap is a 16V part, so it’s no wonder it exploded. You could theoretically install a 25V or 35V capacitor in its place (the regulator allows up to around 27V IIRC), though you’d have to be careful to draw only small amounts of current, lest it get very, very hot.

author: wizard69
author_rank: Super Contributor
timestamp: February 17, 2021, 01:38:02 am
content: I'm glad you got plenty of suggestions to DIY a power supply. A power supply built on a proto board is not a long term solution, but if you are using the common 3 terminal regulators you will learn much. This is key because power supplies cause a lot of problems in the electronics world. in industry more things die due to power supply issues that just about anything else. So even if you primary interests is digital, it really pays to have a good understanding of basic power supplies.Quote from: YurkshireLad on February 15, 2021, 10:59:49 pmIf you look around you should be able to find some boards (kits and assembled) already. It doesn't however hurt to learn PCB production techniques. The 7805 is extremely common but you should also consider what else is on the market. More importantly down load the manufactures data sheets for whatever you do choose to use.Quoteideally you would be using an unregulated plug pack feeding a regulator near your protoboard.

author: bobbydazzler
author_rank: Regular Contributor
timestamp: February 17, 2021, 08:42:00 am
content: I think a power supply for a breadboard built on a protoboard could easily be a long term solution and the OP will learn useful tricks if he doesn't already know. A half/quarter sized breadboard PCB would be perfect for that project because it will be the perfect size and be able to plug into breadboards with breakout pins just like the psu I destroyed.

author: Ian.M
author_rank: Super Contributor
timestamp: February 17, 2021, 11:51:21 am
content: Caution: 78xx series regulators loose regulation if their Gnd pin connection goes open circuit. This means that if you try to use one directly in solderless breadboard, there is a risk of your load Vcc rising to within a volt or two of the input voltage if anything wobbles the regulator causing a bad contact, or your Gnd wire comes loose. To avoid this, you need four wire connection to the regulator i.e. separate input and output grounds. Fortunately the tab is connected to the Gnd pin, so the easiest fix is to connect the input PSU ground to the 78xx tab (use a ring terminal), so the ground connection to the breadboard runs from the tab via the Gnd pin, and if it comes loose, your breadboard looses power instead of getting over-voltaged.N.B. the suggested input and output decoupling caps in the 78xx regulator datasheet are *REQUIRED* and must be as close to the regulator as possible, so plug them in to the three rows of contacts the regulator is connected to. If you omit them or put them too far from the regulator there is a risk it will become a RF power oscillator!Quote from: tooki on February 16, 2021, 08:25:24 pmThe Elegoo 'Power MB V2' breadboard power supply module I have in front of me has a 10uF 25V SMD electrolytic. It uses AMS1117 regulators. Although *SOME* AMS1117 regulators are rated for 30V Abs.Max. input voltage, e.g:https://datasheet.lcsc.com/szlcsc/2001081204_Shikues-AMS1117-1-2_C475600.pdfothers are only rated for18V, e.g:http://www.ams-semitech.com/attachments/File/AMS1117_20120314.pdfso a 16V electrolytic isn't really an issue.Its design is based on theYwRobot breadboard power supply, with the 100uF through-hole electrolytic replaced with a 10uF SMD part, a SMD LED and a polyfuse in the 5V feed to the USB A socket. The 5V regulator feeds the 3.3V regulator so transient input overvoltage is more likely to blow the 5V regulator than anything else.If you feed it from an unregulated 'linear' wallwart there is a high risk of blowing the 5V regulator when you plug in the DC jack or operate the module's power switch, as the unloaded input voltage may easily exceed 18V. Use a regulated wallwart <=12V or check that your unregulated wallwart doesn't exceed 15V with no load.

author: bobbydazzler
author_rank: Regular Contributor
timestamp: February 17, 2021, 12:28:03 pm
content: Yeah I think replacing the input cap with a bigger one and adding an output electrolytic and ceramic caps might be my project for tonight. Is there any danger from the debris from the burst cap contaminating the board or poisoning me?

author: Ian.M
author_rank: Super Contributor
timestamp: February 17, 2021, 12:45:45 pm
content: The electrolyte isn't nice stuff but as long as you don't ingest a significant quantity of it its unlikely to do you any harm. Seehttp://www.elna.co.jp/en/capacitor/alumi/principle.htmlfor a typical electrolyte composition.However it *MAY* cause long-term corrosion problems so after you've desoldered the old cap's legs, wash off the board with IPA and give it a good scrub before fitting the replacement. If you want to fit extra caps, two 10uF 6.3V or 10V electrolytics soldered top-side to the two pairs of output pins marked VCC GND would do the job without getting in the way of the output voltage selection jumpers.

author: bobbydazzler
author_rank: Regular Contributor
timestamp: February 17, 2021, 02:34:01 pm
content: Ok I just repaired mine and discovered I had the same issue as you - 5v voltage output is nowhere near 5v. I measured 6.9v with an 8v 500mA dc jack, I don't know how that's possible unless the 5v output is connected to the output of the input diode?(accounting for the 1v drop from the dc wall jack)

author: Ian.M
author_rank: Super Contributor
timestamp: February 17, 2021, 02:57:45 pm
content: That means the 5V regulator is blown and needs replacement. Not surprising as you overvoltaged it so badly. Its the SOT-223 package AMS1117-5.0, on the centerline of the board. If you cant get it easily you can substitute a LT1117-5 or LM1117-5.0.Also check the 3.3V rail - if that's high as well the other regulator AMS1117-3.3 will also need replacement.

author: Peabody
author_rank: Super Contributor
timestamp: February 17, 2021, 03:11:43 pm
content: My bad YwRobot is ok at 5V but is 4.2V on the 3.3V output. So either regulator can fail. I believe the 3.3V regulator is powered from the regulated 5V line, so it's not clear that it would fail easily. But it clearly did on mine. Maybe I need to investigate a bit more.

author: Jan Audio
author_rank: Frequent Contributor
timestamp: February 17, 2021, 03:54:48 pm
content: Quote from: Ian.M on February 17, 2021, 11:51:21 amIndeed, you need this : gw-instek gpp-4323.Or you can solder the power input and regulator on a experiment-board with some pin headers.This lesson i also learned this week running my DSPICs on 4,38 volt for a moment, they still work.the regulator was on a experiment board while the power is connected with pin headers and breadboard-cables.Best is to use regulators on the same ( mainboard ) as where the power comes in.Important lesson.

author: Ian.M
author_rank: Super Contributor
timestamp: February 17, 2021, 05:03:54 pm
content: Quote from: Peabody on February 17, 2021, 03:11:43 pmIf you instantaneously short the 5V rail to ground, and there's a large capacitance on the 3.3V rail (e.g 1000uf), you can destroy the 3.3V regulator by excessive reverse current through it. A 1A Schottky diode from 3.3V to 5V, cathode positive, will prevent this. Its most easily fitted between the thermal tabs of the two regulators (as both are the outputs), cathode towards the AMS1117-5.0 on the centerline of the board.

author: radiolistener
author_rank: Super Contributor
timestamp: February 18, 2021, 08:35:12 pm
content: Quote from: Ian.M on February 17, 2021, 02:57:45 pmyes, it has very weak 1117-5. My one was burned out just due to short circuit for a second.I replaced it with some ST 5V regulator in the same package.

author: bateau020
author_rank: Frequent Contributor
timestamp: February 20, 2021, 05:59:27 pm
content: Those breadboard power supplies are badly designed and constructed in general. The 1117 chips should be able to withstand shorts, and nicely limit output current to 800mA, but I found they extremely often don't.And shorts on breadboards are very easy to make. I learned it the hard way: a short on the 3V3 line blew both regulators, that in turn blew up a $50 Lidar (<rant>and no, a 5V TVS is not enough, those things will limit the line to 8V, knew it, just thought it would be OK. so NOT.</rant>)So: whenever your breadboard power supply has experienced a short, count on at least one of the lines to have become dangerous for the electronics you want to use it for.2 things I recommend:1) Put a 7805 in place of the 1117-5. You'll have to twist the legs as the sequence of the pins is not the same, but it will make the 5V line much more robust against abuse and will also protect the 3.3V regulator, as now the input current will be limited correctly. Just don't rip it off when you handle the board. See the first image. Jeah, a bit fragile, but so is your breadboard circuit.Down side: your input voltage MUST be 11V-15V, 9V will no longer do. Why? A 7805 needs more headroom than a 1117-5.2) Limit the input current: Use a 12V power supply that is limited to 1A, and/or use a fuse (glass or something like the RXEF090) on the input. You will probably not be able to fit that properly to the breadboard PCB, as the connections go all over the place. There are some breadboard power supplies that have fuses built in, but they are hard to find.In the end, I built my own breadboard PSU. Same form factor, just better protection: selectable current limit via a LM317, backfeed protection diodes, etc. See second image (top side is shown, bottom side has a load of SMD components). Quick and dirty build. Not much to be proud of, but it's safer now.

author: bobbydazzler
author_rank: Regular Contributor
timestamp: February 20, 2021, 08:59:19 pm
content: Quote from: bateau020 on February 20, 2021, 05:59:27 pmNice workThe psu seems fully functional with lots of nice features like the lm317 current limiter. I don't understand why 9v dc wouldn't be enough? I only need 2v above whatever the 78xx output is to safely stay in regulation. Do you have a picture of the backside of the psu? I also don't understand how you get 3.3v from that or am I mistaken?

author: bateau020
author_rank: Frequent Contributor
timestamp: February 20, 2021, 10:16:32 pm
content: Not all 7805 regulators work well with 2V drop. Most manufacturers specify 10V minimum input voltage, only some specify 7V. Add to that the drop over the input protection diode (SS24) that you normally find on the breadboard PSUs, and even 10V MIGHT be too little. Look at figure 29 inhttp://www.farnell.com/datasheets/2307057.pdf(from STmicroelectronics). Optimal output handling is at 5V dropout.About the 3.3V on the version I made (and the 'original' one with the 7805): just a good brand version of the 1117-3.3, behind the 7805.Attached is the schema of my version, and an image from the backside. This was a fast test version, made on my CNC with parts lying around (note the mismatching nuts). Lots of things wrong. The main problems are that the fuse is badly placed, and that the overall voltage drop before the 7805 is too high, meaning that I cannot reach the theoretical current limits, and that power regulation is not really good. The schema has been corrected for most errors, but not yet regarding the voltage drop issue. So not ideal, but good enough for now.

author: MikeK
author_rank: Super Contributor
timestamp: February 21, 2021, 12:27:07 am
content: But you won't be using more than an amp with a breadboard. Or you shouldn't be. Most breadboard projects are going to be fractions of an amp.

author: bateau020
author_rank: Frequent Contributor
timestamp: February 21, 2021, 07:29:39 am
content: Indeed, steady state current should be below 1A. Some circuits will however pull higher currents for very small time periods (ex: at startup charge the powerline caps, leds driven on PWM,..). A 7805 will not clamp at 1A exactly, it can handle 2.2A without problems for short periods (says ST), and luckily so. It is during those high power draw period that you'll see the difference of having some more headroom.Why would that be important? Because starting too slow may cause many problems. If during a slow start, with an already high current draw, you get additional power draw (ex.: esp8266 WiFi connection setup), a badly regulated voltage might drop. This can cause problems for the circuit, like the processor freaking out.

author: Zero999
author_rank: Super Contributor
timestamp: February 21, 2021, 02:20:52 pm
content: You'll need a fair size heat sink for the LM7805, at 1A, which is also too much current for a little PP3 9V battery unless you're talking about a PPG battery, which is much bigger. Even at low currents, the LM7805 isn't ideal, as it needs 7V of headroom to regulate properly, because an alkaline battery will still have plenty of energy left at 7V and it won't be compatible with rechargeable batteries, unless your circuit will work with a poorly regulated power supply, down to 4V.You could consider a switched mode power supply. There are plenty of 5V switched mode power supplies, which will fit into the standard footprint for the LM7805.https://www.mouser.co.uk/ProductDetail/Texas-Instruments/TPSM84205EAB?qs=EU6FO9ffTwebBdE7jpRRHA==&mgh=1&vip=1&gclid=Cj0KCQiApsiBBhCKARIsAN8o_4imkXy5RV0lha3Fyk0zDlWQelTlVsbU-xc3ZSa2DtjoWEflUBWKrBUaAjfEEALw_wcBhttps://uk.rs-online.com/web/p/switching-regulators/7962138/

author: Ian.M
author_rank: Super Contributor
timestamp: February 21, 2021, 04:04:05 pm
content: Any reputable brand of 7805, properly heatsinked will be able to deliver 1A without loosing regulation with only 8V in, (i.e. with 3V headroom above Vout). The SS24 reverse polarity protection diode drops at most 0.5V (@2A), so as long as the input doesn't drop below 8.5V the 5V rail should stay in regulation. If the ripple trough on your 9V PSU rated for 1A out drops below 8.5V its a piece of sh!t, that either needs derating to half the nominal current or even dumping in the eWaste recycling.If you are drawing more than 1A through breadboard contacts you are doing something seriously wrong. If it weren't for the USB A 5V power out socket, I'd strongly recommend a 78M05 to get a safer lower current limit.Switched mode regulators are nice and efficient, but if you've gone to batteries because you need a cleaner supply, the switching frequency ripple may be an issue. Probably the best simple answer is to get a 3S protected LiPO pack and charger and make up a lead with an inline 2A fuse to connect it to a linear breadboard PSU board. It wont take many weekends on the bench to break even vs buying AA alkalines.

author: rfclown
author_rank: Frequent Contributor
timestamp: February 22, 2021, 02:00:40 am
content: Quote from: YurkshireLad on February 15, 2021, 04:33:04 pmI know I'm going again your stated wishes, but I would stongly suggest getting a simple bench power supply. Without it, you are working in the dark (unless you are monitoring voltage and current of your circuit with two meters). Especially prototyping, were it is so common to have shorts, or plain dumb ideas that smoke things. With a bench supply, you can set a current limit so you don't smoke things, and you are always getting a visual on the power draw. Even though at work and at home I have good HP supplies, my go to supplies for low current are these:https://www.circuitspecialists.com/bench-power-supply-csi1802x.htmlThey are quiet, and they are linear, therefore clean (some of these small bench supplies are switchers and horribly noisy)Reading though all the other replies reminds me of the times when I've gone straight to the particular wall wart (or USB connection) that I'm planning on using for a project when I'm in the breadboard phase. Almost without exeption I end up kicking myself for not using a bench supply first. So much frustration and wasted time.

author: YurkshireLad
author_rank: Frequent Contributor
timestamp: February 22, 2021, 02:07:09 am
content: Thanks rfclown. What you say makes absolute sense. I'm wary of spending money on "bigger" (relatively speaking) ticket items at the moment because I'm an absolute beginner, learning about microcontrollers and basic electronics. I don't want to spend in case this hobby doesn't go anywhere for me. If that makes sense. I'll do a bit of research into simple bench power supplies.A quick comment in hindsight; one thing I like about the breadboard power supplies (even though they're not usable), is that I can I have two different power sources, one at 3.3V and one at 5V. So something small, relatively cheap and with the ability to provide two different voltages? Does it exist?

author: nightfire
author_rank: Frequent Contributor
timestamp: February 22, 2021, 03:37:49 am
content: There are some lab power suppplies with an USB port that outputs fixed 5V in addition to the normal channel(s).

author: YurkshireLad
author_rank: Frequent Contributor
timestamp: February 23, 2021, 02:13:48 pm
content: Thanks all.I was thinking of replacing it with one of these:https://www.ebay.ca/itm/Adapter-Power-Supply-9VDC-1A-110VAC-with-Male-5-5mm-x-2-1mm-For-Arduino-2000/254632265583I'll also research power supplies with USB ports, as suggested by nightfire.

author: YurkshireLad
author_rank: Frequent Contributor
timestamp: February 23, 2021, 04:13:24 pm
content: Here's one I haven't heard of before. That's an odd looking beast.https://www.robotshop.com/ca/en/mego-4-24v-breadboard-dc-rechargeable-power-supply.html

author: kallek
author_rank: Regular Contributor
timestamp: February 23, 2021, 04:29:47 pm
content: And expensive for what it is imo.+1 for building your own regulator board and saving money for proper power supply.

author: YurkshireLad
author_rank: Frequent Contributor
timestamp: March 01, 2021, 12:50:15 am
content: There's an absolute plethora of cheap, chinese bench power supplies on Amazon (Canada). How am I supposed to know which are safe, or good or which should be avoided? Many are rebadges of other models. I was looking at those under C$100 before tax.

author: Jan Audio
author_rank: Frequent Contributor
timestamp: March 01, 2021, 03:13:44 pm
content: You can try, then you need to do the test that breaks it within two weeks :https://www.eevblog.com/forum/beginners/test-procedure-for-cheap-lab-supplies/msg3475392/#msg3475392So you normally use it for 13 days, the last day of money back warranty you do the tests.If it breaks dont let them repair your warranty away, go for a refund.

author: kallek
author_rank: Regular Contributor
timestamp: March 01, 2021, 03:44:28 pm
content: This thread have good information about power suplies. There are many other similar threads as well.https://www.eevblog.com/forum/testgear/looking-for-a-bench-power-supply-142871/

author: bobbydazzler
author_rank: Regular Contributor
timestamp: March 03, 2021, 12:10:41 am
content: Trap for young players - If you try to make a power supply on a blank 2.54mm pcb the holes don't line up with the power rails on the breadboard. So unless you can make a pcb like bateau020 or are prepared to buy one it might just be easier to upgrade the original power supply with a 7805 and upgrade the capacitors to 50v ones so the psu can accept higher voltages. You could solder female breakout headers in place of the 5v 1117 to plug the 7805 into so it looks neater.

author: Zero999
author_rank: Super Contributor
timestamp: March 04, 2021, 02:13:48 pm
content: Quote from: Ian.M on February 21, 2021, 04:04:05 pmI just realised I said 7V of headroom, when I meant it requires at least 7V to regulate properly.That's fine if it's an 8V power supply, but no good for a little 9V battery.

author: Ian.M
author_rank: Super Contributor
timestamp: March 04, 2021, 02:51:46 pm
content: Yes a little 9V PP3 battery is *expletive* useless for anything except brief testing. Assuming a AMS117-5.0 or similar LDO fed via a SS24 or similar Schottky diode, (as per original Yrobot circuit), even with a *GOOD* *QUALITY* Alkaline PP3, you wont even get 30mA for two full workdays on the bench. Put any significant pulsed load on it after the first hour or two and it will dip under 6V in and drop out. I use a 6xAA holder with a PP3 clip on it, stuffed with discount Kodak brand AA alkaline. Its still not ideal, but you get over four times the capacity for about the same price as a same brand Alkaline PP3, and an order of magnitude lower internal resistance so much less trouble with pulsed loads.