How to power my little projects, kits... - Page 1
Forum section: electronics / beginners

author: cepwin
author_rank: Unknown
timestamp: October 07, 2017, 10:53:34 pm
content: So to get myself back into actually working with PCBs and soldering (many years ago I built kits, including a heathkit Ham Radio transmitter at summer camp) and see what I'd need to do this stuff I purchased two inexpensive kits, a signal generator and an oscilloscope. I assembled the signal generator but can't test it yet as it of course doesn't come with a power supply, just a barrel connector that takes a 9-12v center positive connection. Since I will need to power it, the other kit and anything else I make I am debating between just getting one of the ac-dc power connectors that is adjustable (ie. multiple voltage settings, multiple connectors) It sells on amazon for $13 (USD). Alternatively I can get a basic bench dc power unit that will run up to 30v and 5amps on ebay for roughly $35-55 (USD). This will be a lot more versatile but obviously more money when you're getting your toes web.This would be single output so I can only test one item at a time....can't feed the signal into the oscilloscope ...for that I''d need one that can power two items. From Dave'svideos they seem to be a basic piece of gear like a multimeter and a soldering iron.Any thoughts?

author: daybyter
author_rank: Frequent Contributor
timestamp: October 07, 2017, 11:14:30 pm
content: Well, for now a 9v battery + cable + barrel plug would get you started?

author: Brumby
author_rank: Unknown
timestamp: October 07, 2017, 11:39:51 pm
content: I would suggest you bite the bullet and get a basic lab supply - one that has adjustable current limiting. The expense isn't that excessive and youwillsoon find yourself being thankful you didn't go for the $13 option.Don't be afraid that getting a cheap lab style supply might be a waste. It won't. If you do get stuck into the hobby seriously and decide you need a dual tracking supply with remote access features, your first supply will still have a place on the bench - and you will still find uses for it. It is common knowledge that you can *never* have too many power supplies!

author: Brumby
author_rank: Unknown
timestamp: October 07, 2017, 11:49:32 pm
content: As far as powering multiple items is concerned - if one item operates between 6V to 9V and the other between 9V to 12V, then you can set your supply to 9V and run them both off the one supply - assuming their combined current draw does not exceed the capacity of the supply.This is another advantage of having a lab style supply .... the output voltage will be regulated. When you set it on 9V, the output will BE 9V. With plug packs, it will depend on the design. Some that say they can do 9V at 1A will actually put out 11V or more with a light load and only drop down to 9V when the full 1A is being drawn.A regulated lab supply will give you certainty on what power is actually being delivered.

author: cepwin
author_rank: Unknown
timestamp: October 08, 2017, 12:09:06 am
content: Thank you all for your advice...I did decide to go with a cheap lab power supply that should work along with some connectors ....we'll see how it goes...hopefully my solder joints aren't too bad and I didn't hurt the main chip (it was a bit of a struggle to get it in....like I said though...it's for pedagogical purposesThank you all again.

author: David Hess
author_rank: Super Contributor
timestamp: October 08, 2017, 05:28:27 pm
content: If you are getting back into electronics, then maybe a power supply kit would be appropriate. I still have and use mine from when I was 16 years old.

author: rstofer
author_rank: Super Contributor
timestamp: October 09, 2017, 01:53:32 pm
content: Using a lab power supply to power a fixed device, like a signal generator or scope, seems like a waste of an adjustable supply. You need the lab supply to power the breadboard!I just use fixed voltage wall warts when there is a downstream regulator. I even put labels on the housing to indicate which specific device they are supposed to power.You can get along for decades without a lab power supply. It's not ideal but you can easily take a 9V wall wart and cobble together a 5V linear supply for projects.By all means, buy a lab supply but get a box full of wall warts as well.

author: David Hess
author_rank: Super Contributor
timestamp: October 09, 2017, 06:53:59 pm
content: The old lab power supply that I mentioned which came in kit form just has a voltage adjustment potentiometer and an analog voltage meter and is a typical 723 and 2N3055 design. I have several fixed output power supplies including a couple of combined +5, -15, and +15 volt supplies that I made for when one of my bench supplies is not needed. I am not a fan of wall warts because of their typically horrendous regulation, noise, and questionable isolation.

author: Shock
author_rank: Super Contributor
timestamp: October 09, 2017, 11:06:07 pm
content: It's easy to stockpile power supplies when you are looking for them, ask family and friends if they have old electronics sitting around or being thrown out. Put an advert on craigslist etc that you are looking for free wall warts or unused PC supplies.For your bench supply you want to eventually get a constant current, constant voltage supply with overload and short protection. You can get away with lower voltages but 0-20V and preferably 0-30V covers most situations. Dual (or two separate) bench supplies are very useful also if they can be setup to provide a positive and negative voltage rail for projects, or situations where you need two voltages at once.This may be useful, it can turn a cheap supply into something more usable. But if you keep an eye out you can get decent quality commercially made bench supplies cheap. So if money is tight consider whats going to give you the best bang for buck long term.

author: adras
author_rank: Regular Contributor
timestamp: October 11, 2017, 02:41:34 pm
content: Quote from: rstofer on October 09, 2017, 01:53:32 pmYep, that's one simple way. I've got a DSO-138 oscilloscope, to power it I decided to use batteries, since the voltage of the batteries was not the one the oscilloscope required I just bought a cheap buck or boost(don't remember which one) converter on ebay. Now I've got a portable scope and don't need to worry about how I can power it.But the more I do with electronics I miss flexibility in these approaches so now I'm looking for a power supply as well. Didn't find anything beefy with 10+ Amps yet though

author: james_s
author_rank: Super Contributor
timestamp: October 17, 2017, 07:55:40 pm
content: Assuming you want to power various projects off the bench, just grab a few old wall warts. Garage sales and thrift stores are a good place to get them, or ebay. I have a box of mostly 5V and 12V ones I use for all sorts of things.

author: innkeeper
author_rank: Unknown
timestamp: October 17, 2017, 08:50:04 pm
content: if i was to start from scratch with little money this is what id do.first id make a couple of supplies by converting some old atx power supplies to bench supplies. (search it there are many writeups on this)id get hold of a couple of those buck-boost digital control Power Supply controllers off ebay or alibaba to give me voltages outside the fixed range, and current limiting... id connect those to the atx bench supplies when needed.all in all you would have a very flexible setup with little work and relatively low cost. especially if you can salvage the atx supplies. .... and that should be easy..

author: MarkF
author_rank: Super Contributor
timestamp: October 18, 2017, 01:21:55 am
content: Similar situation here. I didn't want to adjust my lab supply every time I needed to use my project board.WARNING.. Those wall warts aren't what they say. I have several that are 12V DC outputs. Their actual voltage is 15V. I have two 9V DC output that are actually AC rectified. Not even filtered let alone regulated.

author: Naguissa
author_rank: Regular Contributor
timestamp: October 18, 2017, 05:04:35 am
content: Both: bench for testing devices and, when you confirm all is ok, you can connect them to plugpack and use bench for testing other device.Enviado desde mi Jolla mediante Tapatalk

author: Awesome14
author_rank: Regular Contributor
timestamp: October 18, 2017, 05:05:36 am
content: Quote from: MarkF on October 18, 2017, 01:21:55 amIn the past, wall warts were simple rectified AC. Unless they were loaded properly (i.e. just using a meter as the load), the output voltage was higher than the rating. Today, most wall warts are SMPS, so they output the same voltage all the way up to their current rating.In reference to the OP: Cheap power supplies are OK. They're less stable and dirtier than more expensive models. I have a box of old wall warts. They always come in handy. But I also have (4) variable power supplies: Lamda 60V 15A, (2) Sorensen 15V 4A quad, Chinese 30V 3A. And I have a few fixed voltage supplies.

author: innkeeper
author_rank: Unknown
timestamp: October 19, 2017, 04:22:02 am
content: Quote from: MarkF on October 18, 2017, 01:21:55 amthat is one of the reasons i love the ATX power supply conversions, +/-12 +5 +3.3 runs a high percentage of what i play with.and all for FREE out of any old pc,

author: xani
author_rank: Frequent Contributor
timestamp: October 19, 2017, 11:30:25 am
content: If you don't already have any I'd go with lab power supply, or the $20 module + any reasonably high voltage salvaged power brick (or PC PSU but that's more work, most need some load to even work propertly , on top of that it is ground referenced and you do not want that in power supply)It is just so much more convenient to be able to test circuit at any voltage, or start with with some few tens of mA current limit to make sure you didn't. You will get a lot of use out it.As for powering your little projects, I'd just go with a bunch of 7805/9/12 on a piece perfboard together with some sockets and put it in a box, it's a cheap and easy project to make and you can expand it to as many voltages as you need

author: MarkF
author_rank: Super Contributor
timestamp: October 19, 2017, 11:45:56 am
content: Quote from: innkeeper on October 19, 2017, 04:22:02 amI actually bought thisATX Breakout Board for Bench Power Supplyandcase. But never had a chance to use it.Edit. The breakout board has "1.25 amp polyfuses with reset on each power rail". A good thing to have if you use the ATX power supply as a bench supply. You don't want 10's of amps burning up your little project while testing.

author: kalel
author_rank: Frequent Contributor
timestamp: October 19, 2017, 11:50:48 am
content: Good thing about the breakout board is that it's non destructive.But, for the price, a step down (voltage adjustable) converter can be bought with a display showing the outgoing voltage and current. Perhaps even a voltage/current adjustable module. Of course, you would get more amps if driving directly using the breakout board.

author: Richard Crowley
author_rank: Super Contributor
timestamp: October 19, 2017, 12:22:27 pm
content: Your test gear should have their own dedicated power supplies, whether battery or mains-sourced. That way you are not dependent on sharing/swapping power sources between the gear and the project. Even just a 9V battery clip to DC power connector cable is only a few cents from China.Even if you have to buy NEW "wall-wart" (or "line-lump") power supplies, they are literally only a few bucks and seem like a minor expense. However, you should be able to collect these things essentially for FREE from consumer gadgets that are being discarded.Developing a good "junk box" of discarded electronics is one of the major parts of the electronics hobby IMHO. There are likely hundreds of videos on YouTube about scrounging old discarded consumer gadgets and harvesting components for re-use/re-cycling. And a major part of that is the power supplies, whether external wall-wart or line-lump, or internal linear or switching supply sub-assemblies, etc.If I were starting from scratch, I would put these at the top of my list:Digital Multi-Meter (DMM) - even a $10 gadget from Harbor Freight, etc. would be a start. You can always get a better one and you can't have too many meters. You can't hardly do anything in electronics without at least this basic piece of kit.LCR Transistor Diode tester - These used to be called "The $20 LCR tester" but they are now available well under $10. An absolute bargain for the price and an essential part of any modern electronic hobby bench.Power Supply - Whether recycled wall-warts or battery clips or an adjustable "bench supply". Again you probably can't have too many power sources. Those little modules as featured Dave's recent video are a killer solution. An amazing bargain for the price. Highly recommended.

author: Mr. Scram
author_rank: Super Contributor
timestamp: October 19, 2017, 12:52:33 pm
content: Quote from: Brumby on October 07, 2017, 11:39:51 pmThe latter also applies to multimeters, and probably an array of other tools.

author: cdev
author_rank: Super Contributor
timestamp: October 19, 2017, 01:22:38 pm
content: As far as a DMM goes..It seems the low end Aneng 8008 stands out in terms of value and can be had for around $15 or so. I would get that one.I have a Unit-T UR61E DMM which gets a lot of use. It stand out on value in its price range if you only do low voltage stuff (like me). It was around $50 on ebay.Also, a few months ago I bought a $2 voltage regulator "breadboard power supply" from China (manufactured by yuwibot (?) or something like that) that clips to a breadboard and supplies 3.3 volts (or 5 volts) if you plug an external wall wart that supplies 7-12volts to it. .Its convenient and it works, however you should remove the USB connector from it or put tape over it.It has several issues which you can Google about/for.Still, its useful for powering standalone breadboard 3.3 volt projects..For my soldering iron I am currently using a cheap clone of a Hakko that adds digital temperature control. Its a mixed bag. It was around $40 from mjpa.com here in the US.Similar irons are much cheaper on ebay. I have a bunch of tips for it and they make it much better than it would be otherwise but it still has an issue in that the thermal contact between the heating element and tips could be better and there really is little I can do at this pint to improve that.That means the temperatures it reads are inaccurate. I didn't realize this for a while as a beginner.So now I am hoping to find a Hakko FX888D on sale somewhere.Other very useful, very cheap tools.. I have an "AVR Transistor Tester" from ebay.. (see this article - as well as a huge thread here- for more about it:https://www.mikrocontroller.net/articles/AVR_Transistortester#Introduction_.28English.29) Its extremely useful for things like ESR testing of old capacitors. I paid around $15 on ebay but now they can be found for as little as $7.They also test inductance - capacitance - most semiconductors and identify the relevant parameters of around 90% of unknown or private labeled two and three terminal parts.The ESR testing capability is essential for repair of old electronics.I also have an old Tek scope, one of the first models with any DSO capability but it is basically analog... Its a classic, kind of but it takes up a lot of desk space.. so right now its usually used sitting on the floor with is screen facing up. A non-optimal setup.I also have a cheap, generic (Sigrok.org) -Pulseview-compatible 8 channel logic analyzer - You can find them now for $10 or less.. Its really useful.An adjustable constant voltage/constant current supply is kind of essential when you are doing low voltage stuff, because the adjustable constant current can prevent a wrong connection from damaging precious parts. The module in the recent video has adjustable current limiting and would do this adequately.(before you connect power to your circuit, limit the current in the circuit to what it is supposed to be plus maybe 15-20% even if something inside your device shorts the power supply rails. This won't have any effect unless that current level is reached. Then, it will limit the current at that value.)I have a bunch of breadboards of varying quality.The smallest ones get used the most. If you can afford to buy good quality breadboards its worth it.Its good to have a bunch of test leads of various kinds. Also, solid hookup wire (for breadboards, especially) and some "dupont cables" short color coded jumper wires with female or male headers make it easier to use them as intended. Use the color coding to identify different kinds of connections. It makes it much easier to keep track of what's going on in a circuit.For a soldering iron I would make sure the tip is grounded and the tips interchangeable. I would start out with a hakko clone but make sure you get a good value and pay the least for that clone.I recently got an assortment of tips which contained most of the popular shapes for less than $5. It was a knock off but so far the tips have held up well.That makes all soldering much easier, having the proper tip for what you are doing.If you can spend a bit more to get a Hakko Fx-888d - by all accounts do it, it appears to be worth the money. (around $100) if you do a lot of soldering.The temperature it shows is more accurate, its thermal transfer is tighter, and much better regulated. Making it more of a pleasurable experience for the user. Otherwise once you realize your soldering oron has this thermal lag you're going to need to keep adjusting its temperature to make up for that shortcoming and you'll realize that its potentially bad for components to be exposed to higher temps than they should be as you attempt to make up for the thermal lag.Its good to also have other means of heating boards while you are soldering them available.

author: iainwhite
author_rank: Unknown
timestamp: October 19, 2017, 01:48:45 pm
content: Quote from: cdev on October 19, 2017, 01:22:38 pmThe breadboard PS you mention is made by "YwRobot"The USB connector is intended to supply 5v from the regulator but there are reports that in some cases it is connected to the barrel jack and therefore could be supplying 12v (or whatever your wall-wart is rated)Like you say, on mine I just leave the USB unconnected

author: Mr. Scram
author_rank: Super Contributor
timestamp: October 19, 2017, 01:58:46 pm
content: Quote from: cdev on October 19, 2017, 01:22:38 pmUnless you are a student with no money to spare, I would advise to buy something half decent and safe first go. I have mucked about with modules a long time, but regret not upgrading to a proper supply sooner. There's also something to be said for a beginner to have a properly safe multimeter, rather than one that's excellent if you know what you're doing. A Brymen BM257 should satisfy all your beginner and more advanced need and can be poked into domestic wall sockets, without much possibility of the user perishing, and for a very moderate price. It's at tool you will enjoy for years.Those breadboard power supplies can be useful, but are not without their risks and pitfalls. I killed all three within two weeks of experimentation. Just a dead regulator, but having current limiting is definitely useful.

author: cdev
author_rank: Super Contributor
timestamp: October 19, 2017, 02:19:57 pm
content: He's right on the power supply. (I do think that the UT-61E is safe for the way I use it and even if I was testing mains voltage- which I'm not, which where I live, in the US it is 115 V. which is half that in the EU and Australia.)On a bench supply, I think having current limiting might well pay for itself pretty quickly if it prevented damage to some fragile device. (if it fails or is hooked up improperly)The module Dave talks about in his video can be used with an unregulated DC supply to make a nice but very cheap current limited bench supply for around $20. (That's including most of the other parts, and assuming one has some junk box parts- common ones.)That's arguably now the best low cost option. However, because it contains a buck converter (a kind of switching supply) it may need more filtering than it has for many things, and I don't know how it would be best to add it to preserve the current limiting.Its true about how you can always use a decent power supply. It would also be good to add a beeper that would give you an immediate audio indication when current through it exceeded its set value.Thats why I like having an analog DMM around, to keep an eye on the variations in drawn current.Quote from: Mr. Scram on October 19, 2017, 01:58:46 pmThe $15 Aneng 8008 is as good as it gets for that tiny amount of money. I would go for that one.

author: MarkF
author_rank: Super Contributor
timestamp: October 19, 2017, 02:21:41 pm
content: I have severalHP 6216A Variable DC Power Supplies. Small (3"Hx5"Wx7"D) with current limiting and multiple units can be put in parallel or series. Not a lot of current but enough for most small projects. Good starter. I would NOT pay much more than $60 with shipping included. I have found them cheaper.

author: Mr. Scram
author_rank: Super Contributor
timestamp: October 19, 2017, 02:29:25 pm
content: We've had the discussion about the AN8008 or other cheap multimeters elsewhere on the forums many times. I feel that a beginner should have more leeway than a more advanced tinkerer, simply because he doesn't quite know how to stay out of trouble yet. You can't ask a young player to stay away from danger if he doesn't quite know how.A good example was also given: a car battery typically is only 12 volt, but can push a massive amounts of amps. A novice might equate the low voltage to low current and absolutely melt his multimeter or leads in a violent fashion.

author: xani
author_rank: Frequent Contributor
timestamp: October 19, 2017, 02:56:54 pm
content: Quote from: Mr. Scram on October 19, 2017, 02:29:25 pmAN8008 does have fuse on 10A range, (which seems to be rare with cheap meters) so connecting it to 12V wont make meter melt.

author: cdev
author_rank: Super Contributor
timestamp: October 19, 2017, 03:07:18 pm
content: This one is quite nice to use when its current is enough because its a small linear supply with a big heat sink that's completely silent. No fan.Quote from: MarkF on October 19, 2017, 02:21:41 pm

author: cepwin
author_rank: Unknown
timestamp: November 18, 2017, 12:26:33 am
content: Thank you all for your replies. What I ended up doing is getting an inexpensive bench power supply that seems to work pretty well for what I'm trying to do. Thanks again!