Power Supply for Home lab?

I've designed and built many power supplies in my lifetime and if you want something simple that's premade then e14 has reasonably priced adjustable and programmable power supplies.

The Tenma  72-253572-2535 is a good start with both Constant Voltage and Constant Current modes

With both modes available it is very easy to use it to test LEDs.

Another handy tool to have is an accompanying DC load unit as this will enable you to properly test power supplies and batteries)

LOOkatu .. I'm going to build it myself.. MAKE IT MYSELF..
Thanks COMPACT

mudz

I was going to keep out of the RedP aspects of this thread but now that I've been asked ........

The RedP is an interesting attempt at a low cost instrument based on the Xilinx Zynq chip. It was massively over-hyped on it's launch with claims that it could replace instruments costing 10s of k$. The current web site is a bit more restrained  but still sadly lacking in detailed specs.

To take the inputs : a real scope has a wide bandwidth amplifier and either a switch or other means of selecting a wide range of gains so that the sensitivity can be set between a few mV per vertical division to perhaps 20V. As you pay more the ranges extend a bit and the precision and bandwidth improve. The other key feature they offer is some kind of DC offset control before the ADC - this is really useful. The RedP offers 20V or 1V, jumper selectable, and I'm not sure if its 1M impedance on both ranges. This will be so inconvenient that you will very quickly get totally fed up with it and either try to build an input amplifier/attenuator (which is very difficult) or give up and buy a real scope.

The RedP samples at  14 bits at 125MHz -  this is very slow - the cheapest Rigol samples 8 bits at 1GHz which is a much better compromise for a general purpose scope.

Try comparing the published data sheets of Pico, Rigol, Kesysight, Tektronix and LeCroy scopes with the RedP data - it's quite instructive - worry about the bits that don't get mentioned (and assume the worst).

The closest almost real scope to the RedP would be one of the Pico offerings (they do have proper switching ranges and input amps).

Remember that for useful work you need to be sampling at 10x the working frequency, so the RedP is good for up 12.5MHz.

I don't know anything in detail about the Bitscope - it's pretty cheap but I wouldn't want have to use one.

My advice is always to buy a real scope - if you can't afford  a new one then buy a second hand one.

I practice what I preach - my main scope cost more than my car - but I couldn't do my work without it.

MK

To MK,

Thx for your Candid Assessment on the RedP as opposed to Real Oscilloscope(s). Truth be told I am somewhat of Techie (having a BSEE from 1973) but I am looking for a "overview" Product. Not to get into the Nitty-Gritty of Designing/Testing, but some product that has the Basic Functions that show (maybe in a Limited way) Electronic Instrumentation. An Analog in Chemistry would be "Qualitative Analysis" Rather than "Quantitative Analysis". I am a USPTO Registered Patent Attorney, so my interest in what is available at any given Time/Place will (hopefully) constitute Prior Art. You have given me info about specs & capabilities that Must be considered (taken into account) when I evaluate the RedP to my (uncertain) Needs. Thx Again.

BTW I do have an actual CRT Oscilloscope. It is a Sony/Tektronix Dual Channel "Portable", circa early 1980's. It is under 30 years of Dust.

-USCDADNYC (NY NY USA)

Red Pitaya's main user interface is via the Ethernet port and is presented as a set of WEB pages, not X Windows or anything.

It does have SSH etc available to it and can have additional apps installed / compiled on it

Most of the Pitays analogue/signal processing functionality is handled by the FPGA, this is how it gets its great speed in processing of the inputs and outputs, the price of this is it runs very hot (Over 60deg C)

Right now, the Pitaya has the following main apps available (Some have multiple options and some you have to pay an additional fee for so it may not be as cheap as it appears

2 Channel Scope with the limitations michaelkellett has mentioned ( IE, 12Mhz ish true bandwidth assuming a 10X sample rate)

2 Channel Spectrum Analyzer

2 Channel Signal generator / Arbitary Waveform Generator upto the 125Mhz sample rate again but limited to less than a volt output (TBC)

LCR/reactance meter

Software defined Radio (New and I have not tested this yet)

you can run the ARB and Scope at the same time as there available in the same app, you cant run more than one app at a time on the main WEB pages due to locking of the IO devices like ADC etc I guess

The ADC and DACs are 14bits which is way better than most scopes these days (There all typically 8 bit), one benefit of this is that you get extra resolution out of a range compared to a reg digital 8 bit scope so this can in a limited fashon make up for no sub 1V range for instance as at 1V there is a 1/16384 V resolution... 61uV, this is way better than most scopes and is close to comparable with a 10 - 15mV range on a scope (15mV range would equate to a resolution of 61uV too) so perhaps to be fare we would round that up to a 20mV range. The point here is that any 8bit scope is not that accurate as it only resolves to 256 levels of a signal, scopes are primararly used to Look at the signal and get an idea of what it is doing

If your going to always or mostly be looking at logic level type signals or atleast limited to low voltages then 20V is not too bad but this is the base range, add a 10X probe and guess what, thats 200V. The input t the Pitaya is 1Mohm as mike sait which makes it ideal for adding a 10X probe if needed

Other features are DUAL SATA ports, a full set of GPIO so you could use it as a logic analyzer or control, Matlab / LabView capability, Scratch pogramming, and you could add your own custom apps too if needed, with our without leveraging the FPGA

Ill have more once I have done the review but thatshould help fo now

Oh, forgot to mention, Mine came from RS-Components for me to review so I did not have to buy it.  but you can get from Mouser, Direct from RedPitaya, from Eletor and a few other places. Oh and of course RS-Components. I did not find it on Newark though... sorry

WRT to my Q5 and collateral Q5A,5B, etc. I think I have an answer to my own Q's

The Wiki on Red Pitaya has a table of Ports, (partial listing here)

"

EthernetFull-duplexRJ451000Base-T Ethernet connection

USBFull-duplexA USB Used for standard USB devices

Micro USB (Console)Full-duplexMicro B USB Used for console connection

Micro USB (Power)InputMicro B USB 5 V / 2 A power supply

Micro SDFull-duplexMicro SD slot Micro SD memory card                         "

The "Micro USB (Console)Full-duplexMicro B USB Used for console connection" is the One USB

port to use (for a wired connection from PC/Laptop to RedP) No settings to change OR Cross-over

needed. Just a Male-full-size A -to- Male-micro-size B Cable.

Sorry about the confusion

USCDADNYC (NY NY USA)

Hi Edward,

Many thanks for you wealth of information.

As you are a registered Patent Attorney are you able to give our members some guidance of the Patent process?

I think it would be very much appreciated.

Compact

Kudos to Both PO & MK. You guys are the BEST. You guys cut down to the Chase w/o hyperbole. W/ the info gotten from you two, I can get a PhD in Oscilloscope (and wannabe's) Technology.

To PO:

PO wrote>>... [RedP has ]a full set of GPIO so you could use it as a logic analyzer or control...

ELY reply>> You just brought to Memory Lane again. In the 1970's, I had built a "Kit" Logic Analyzer. It was Only  8 bits.

USCDADNYC (NY NY USA)

WRT Patent Advice, it will be just General Outline(s) of the Patenting Process. Like they say on TV, paraphrasing, " I am a patent Atty, BUT do Not play one on this Blog."

However, I would have to know what Legal Jurisdiction(s) [Nation] you guys are in? Luckily the Patent Laws of the US were just harmonized w/ European/English-Speaking Countries, via the USA AIA (America Invents Act) of 2011. Luckily, we are Not talking Drug Patents or Patent Law in (say) India or China. WRT I can only say WTF?

uscdadnyc (ny ny usa)

Compact's in Australia.

In addition to a standard patent we have a local thing called an Innovation Patent that lasts a maximum of 8 years.

These patents are supposedly granted without examination however these patents are only legally enforceable after examination and certification. (As you said WTF?)

We've also got an alternative process called Provisional Application which is designed supposedly to allow the applicant up to 12 months to get the Patent application lodged.

Compact wrote>>...

We've also got an alternative process called Provisional Application which is designed supposedly to allow the applicant up to 12 months to get the Patent application lodged.

ELY Reply>> Same as in the U.S. Being such, I assume that the (required) Specification [detail description of the invention] will support the "Claims" later drafted w/i 12 months, in order to turn the Provisional into a Regular Australian Patent Application. Like the famous WWII US General MacArthur said "the Corps. The Corps. The Corps,

so it is in Patent Law, "The Claims. The Claims. The Claims.".

Compact wrote>>...

In addition to a standard patent we have a local thing called an Innovation Patent that lasts a maximum of 8 years.

These patents are supposedly granted without examination however these patents are only legally enforceable after examination and certification. (As you said WTF?)

ELY Reply>> Interesting this "Innovation Patent(s)", I suppose it is the Australian Patent Office attempt to spur the pace of Innovation. I guess the holder of an Innovation Patent Application, can use it as a Sword under the rubric of: "Patent Pending". Another words, any possible Infringers are on Notice as of the date of filing of the Innovation Patent Application. And Damage can start from that point in Time.

Thx for the Input. Like I said b/f , it is always interesting to converse w/ you

USCDADNYC (NY NY USA)

Compact wrote>>...

We've also got an alternative process called Provisional Application which is designed supposedly to allow the applicant up to 12 months to get the Patent application lodged.

ELY Reply>> Same as in the U.S. Being such, I assume that the (required) Specification [detail description of the invention] will support the "Claims" later drafted w/i 12 months, in order to turn the Provisional into a Regular Australian Patent Application. Like the famous WWII US General MacArthur said "the Corps. The Corps. The Corps,

so it is in Patent Law, "The Claims. The Claims. The Claims.".

Compact wrote>>...

In addition to a standard patent we have a local thing called an Innovation Patent that lasts a maximum of 8 years.

These patents are supposedly granted without examination however these patents are only legally enforceable after examination and certification. (As you said WTF?)

ELY Reply>> Interesting this "Innovation Patent(s)", I suppose it is the Australian Patent Office attempt to spur the pace of Innovation. I guess the holder of an Innovation Patent Application, can use it as a Sword under the rubric of: "Patent Pending". Another words, any possible Infringers are on Notice as of the date of filing of the Innovation Patent Application. And Damage can start from that point in Time.

Thx for the Input. Like I said b/f , it is always interesting to converse w/ you

USCDADNYC (NY NY USA)

To ALL:

We all get product placement Ads (if we allow Cookies. And I do). One product intrigues me. It is a SMPS by Tenma # 72-9470, 13.8Vdc. Why 13.8Vdc? What is so special about 13.8Volts.? I know I am not very current (no pun intended) on Pwr Supplies, but can somebody help me here?

Good Thing I am not Superstitious, but the Tenma Part # has the elements of my Street Address. Weird, You can't make these things up.

USCDADNYC (NY NY USA)

It's an old-school thing, an anachronism. Due to the chemistry of lead acid batteries, they are conveniently chargeable at around 13.8V for a 12V nominal lead acid battery. So old school chargers were literally just a resistor and a 13.8V supply. Today trickle charging can still just be done with a (higher value) resistor, but back in time the accepted approach for normal charging was to use a 13.8V supply. Nowadays this would not be done, there are constant voltage and constant current phases that are observed, and they vary for different battery chemistries.

But in earlier times that would have been expensive to implement.

So, a lot of radio gear (radio being nearly synonymous with all electronics hobbyist activity) at that time could handle 13.8V. The supplies are still made, and any 12V automotive electronics will be able to run off that supply.

Way back when we had systems out in the country, they used Lead Acid batteries, and 13.8v was the 'desired' voltage to recharge them.

The comment was something along the lines of recharging at the fastest rate without causing undue stress ....

The trouble was many of these systems stayed at near full capacity, so all the 13.8v did was boil off the electolyte and the battery would be dry everytime we checked it.

We reduced the voltage to 13.4v and never had an issue or dry battery.

I've always used 13.4v every since.

Mark

For those who did NOT sign-up for the first (of 5) courses In "Intro to Power Electronics" hosted at www.coursera.org. Professors are from Univ of Colorado [USA], the course is pretty Good. They even give you a Link to get a copy of "Ltspice". IDK how fully functional is this copy is, but it is worth getting Nevertheless. For my professional needs this Ltspice and my Paid Student Copy of MatLab/Simulink are more than adequate to give me a handle on current technology in electronics. I am always looking out for what will possibly become Prior Art.

USCDADNYC (NY NY USA)

LT Spice is free to anyone - if you get  chance then go to one of the Linear Technology lectures about it, delivered by Mike Engelhardt, I went to one in Edinburgh (part of the 2014 LTspice World Circuit ) and it was one of the best lectures of its kind I've ever attended.

Sorry about the random font changes - blame the E14 editor !!

MK

Click on the HTML icon and remove the unwanted tags!

LT Spice is free to anyone - if you get  chance then go to one of the Linear Technology lectures about it, delivered by Mike Engelhardt, I went to one in Edinburgh (part of the 2014 LTspice World Circuit ) and it was one of the best lectures of its kind I've ever attended.

Sorry about the random font changes - blame the E14 editor !!

MK