Min/Max Voltage & Ampere Requirements for DC Power for Digital Design/EE  Work - Page 1
Forum section: electronics / testgear

author: 1lulu2
author_rank: Newbie
timestamp: July 15, 2016, 02:50:45 am
content: Hi,I am looking at purchasing the Rigol DP832A power supply. I am new to digital design/EE, and there are so many products out there with different voltages and amps, but I have not found anywhere online what are min/max DC voltage & amp requirements for doing various digital design/EE projects.Is 30V and 3A plenty? Is 100mV and 10mA plenty? Why would I need higher/lower voltage and amps for digital design/EE projects, etc. I want to cover all my basis, so I don't have to purchase another power supply in the future, etc. Forgive me if this question has been asked before!Also, it would be nice if someone could list types of digital design/EE projects, or technology requiring min/max voltages and amps for purchasing the right DC power supply(s).Also, the min/max display resolution (number of digits) required for digital design/EE projects, or technologies, etc., and accuracy too.1lulu2

author: Assafl
author_rank: Frequent Contributor
timestamp: July 15, 2016, 12:03:20 pm
content: For digital, 5V or 3.3V (or similar) voltages are needed. Some digital technologies (like CMOS) can tolerate higher voltages as well. I am talking about "hobby friendly" type digital electronics (the kind that will work on a breadboard like ARM, AVR, CMOS etc. - unlike Intel desktop processors or NVidia video processors that must be designed in the context of a reference design by a design department)....Embedded is a whole different matter. An embedded GCODE controller (e.g. for a CNC and 3D printer) may require a 12V or 24V supply to power peripheral equipment. If you connect the embedded controller to the real world (in the case of a CNC to motors and sensors), the power requirements will increase to whatever is required to operate the device. In some cases, you may need a separate supply (or supplies) for the peripherals (e.g. motor drivers and heaters) and one for the electronics.So, as an example, for a 3D printer, you'll have quite a few watts for the motors, some 40W for the hot end, and over 100W for a heated bed. It dwarfs the power required to run the actual AVR or ARM and supporting circuitry.Lastly, if you are doing analog work (and by analog one also includes mixed-domain - as in an analog input with conditioning, and then an A/D D/A and processing) you may need a symmetrical supply - so a +-18V supply coupled with a 5V/3.3V for the digital section.Ripple and regulation are important in power supplies - the lower the ripple the better (especially for analog work). Accuracy of the display? not as sure about that one. If I have sensitive electronics I always measure with a good DMM. If I need to measure power (rather rare for me) I will use a power DMM - I use a GMC and hope the Mooshimeter will be stable enough for this purpose.I own a nice 2 output 15VDC @1A adjustable "portable" power supply which I use to design with (http://controlresources.com/dual-12-vdc-variable-bench-top-power-supply-labpower/). If I need higher power I will either design one in later or get a cheap one from a surplus store. If I need more voltages - I add wall warts and/or an open frame regulated supply (Condor, etc) I typically get from a surplus store.For reference, I own multiple DMMs, Digital Oscilloscope, a Metcal soldering iron, an LCR meter (not as much for digital work), lots of various style test probes (so I can reliably and safely connect to any signal I'd like to trace), a Scopemeter (for scoping hazardous voltages and power supplies) etc.That said, were I gifted a Rigol DP832A, and had place for it (which I don't) - I wouldn't say no. A real power supply is a convenient beast...

author: nctnico
author_rank: Super Contributor
timestamp: July 15, 2016, 01:34:42 pm
content: For most tasks a 30V 2A power supply is more than sufficient. IMHO a cheap linear supply will be better than a switching one. The cheap switching ones may inject lots of noise into a circuit making it difficult to measure signals. More importantly: a power supply should not produce a spike at turn on/turn off.What I find a handy feature is the ability to disable the output with a toggle switch. This is very easy to add by adding a switch which shorts the voltage setting potmeter. 5 or 10 turn potmeters are also handy.

author: billfernandez
author_rank: Regular Contributor
timestamp: July 16, 2016, 04:21:50 am
content: I think the Rigol DP832A is an excellent general purpose lab supply for electronics work.

author: rstofer
author_rank: Super Contributor
timestamp: July 16, 2016, 04:47:21 am
content: Quote from: billfernandez on July 16, 2016, 04:21:50 amThat's my next purchase. I fool around with op amps so a +- 15V supply is required (I'm not working with single supply circuits) and a fixed 5V supply will work for just about everything in digital because I can always buck it down to 3.3, 2.5 or 1.8. In fact, chips for that very purpose are available and considering the requirements of the FPGAs or uCs, they are just about required. Timing appears to get critical.

author: Assafl
author_rank: Frequent Contributor
timestamp: July 16, 2016, 08:22:18 am
content: Is a bench DC power supply a essential component for someone new to Digital Design? The OP says:Quote from: 1lulu2 on July 15, 2016, 02:50:45 amI admit I don't know the circumstances (wealth, been doing analog design for 20 years, whatever have you...) - but IMHO a good DMM, a good scope, even a logic analyzer, sets of probes, etc. in my book precedes a bench power supply (as nice as it is).IMHO - It is far easier to debug a design powered by a reasonable quality wall wart using a DMM and a scope than powered with a bench power supply without a DMM nor a scope... Just my two cents for some new into the hobby...

author: nctnico
author_rank: Super Contributor
timestamp: July 16, 2016, 08:33:09 am
content: The problem with a wall-wart is that (IF) it is a switching one and it outputs half the mains voltage through it's input filter. This is likely to kill circuits!

author: rstofer
author_rank: Super Contributor
timestamp: July 16, 2016, 05:35:31 pm
content: Quote from: Assafl on July 16, 2016, 08:22:18 amThis is absolutely the case! I have been messing around with electronics for over 60 years and seriously for 40 or more. If I buy the DS832A, it will be my very first bench type power supply. I have used fixed voltage linear supplies (usually 5V), 7805s, wall warts, whatever, but I owe myself a bench supply. This may be the year.I would certainly put almost everything else ahead of the bench supply. OTOH, I find switching supplies to generate too much noise and I really need dual supplies for op amp circuits so I will be buying a bench supply. But it's more a matter of 'because I can' than 'I can't get along without it!'.

author: Berni
author_rank: Super Contributor
timestamp: July 18, 2016, 11:26:06 am
content: I have a Rigol DP832 for some years now and i can say it is a very good bench PSU. Certainly one of the best bang per buck deals of lab supplies.Its has a very standard 30V 3A output that will run most things fine. You get two channels so you can easily make a +/- supply for opamps and that still leaves you with the 3rd low voltage channel to provide power for any digital stuff you might also have in your design. But this 3rd channel is a fully featured channel, on a lot of lab supplies this 3rd channel is fixed at 5V or perhaps switchable between 5V and 3.3V only along with a a fixed few amp current limit, making it a lot less useful.You tend to very rarely need more than 30V on a daily basis in electronics and you can still series two 30V channels together to get 60V. Similar story for current, but if you think you will play with things that might use a lot of power like big DC/DC converters, things with large heaters or motors and such in it you could consider getting another high power single channel PSU the future. For that case i have a old HP 6032A (60V 50A 1kW) that i scored for cheep on ebay. It gets very little use and its huge and heavy.So yeah in conclusion you can hardly go wrong with that Rigol. It has plenty of juice for the vast majority of lab PSU uses. Also you will thank yourself later on when you see how nice it is to have an actuate volts and current display down to 1mV and 1mA right on your PSU aswell as being able to punch in settings on a keypad. Just punch "5" and then "V" and you have 5V rather than twiddling a dicky pot around.EDIT: Sorry meant the non A version. Got it mixed up.

author: rstofer
author_rank: Super Contributor
timestamp: July 18, 2016, 02:20:05 pm
content: And search the forum for the hack to convert an 832 to have all of the features of an 832A. It's done all the time and works well (by all accounts, I haven't done it myself). The same hack, in concept, is done to get the added features of the DS1054Z (100 MHz and all decoders).

author: bitseeker
author_rank: Super Contributor
timestamp: July 19, 2016, 12:20:57 am
content: Quote from: 1lulu2 on July 15, 2016, 02:50:45 amThat should take care of most things you'd need a power supply for.QuoteThat's because there are so many kinds of EE projects. No single power supply will cover every possible thing you might design or build. The "best" choice is the one that fits what you're working on. So, you should have some idea what you'll be designing.QuoteFor most things, probably. But not for everything.QuoteFor most things, no. But could be fine for some things.QuoteIt depends what's needed by your application, the design of your circuits, and the components contained therein.QuoteUnless you have a huge budget, you can only cover all the bases that fit the needs of the types of projects you're likely to work on. So, that's where you have to start. What are you designing or hoping to design and build?QuoteThat's OK. It's been asked many times before, but the best way to get a good answer is to define what you intend to design and build. Then, appropriate recommendations can be made. Otherwise, only a best guess can be used, which may or may not be the best thing for you.QuoteThere are many. It's still best to provide us with what you want to work on. It'll likely be a much shorter list.QuoteA power supply with no display at all can serve you well. You should have a DMM for measuring what your circuits are doing and it can tell you what your power supply is outputting. Fancier power supplies cost more and are more convenient, but not a requirement.As has been recommended, get a linear power supply for clean power. Unless it's in bad shape, it should be accurate enough for general use. Again, without knowing what you want to design, it's hard to say if high accuracy is an important factor.

author: rstofer
author_rank: Super Contributor
timestamp: July 19, 2016, 12:43:20 am
content: Suppose I build a bigger analog computer with, perhaps, 20 LM358 integrators. That's going to take about 60 mA TOTAL from the +-15V supplies. Somehow, I don't see myself running out of capacity on those supplies.Most of my 5V needs (Raspberry Pi, FPGA boards, uC development boards) some in well under 2A. And most (all) of them are powered by wall warts.I can't imagine using 1A on the +-15V supplies. Maybe I could use a couple of amps at 5V but that's about it.I just don't see an issue with capacity. All I need to do is decide to part with the money...I also converted a PC ATX supply with binding posts and fuses. I can deliver a lot of unmetered power if needed.https://www.sparkfun.com/products/12867What I expect is to be able to measure the current while controlling the voltage. That's really my goal - how much current does 'xyz' take.