Signal Generators on Ebay

[MrWizerd]

I am new to EEVblog but got hooked when I saw my first video I watched by Dave.  My professional history is in computer/network  tech, I started back in the late 90's and repaired boards and such when necessary (Most computer techs I know these days just replace not repair in contrast)  Something I like to do in my spare time is build models, I used to do mostly wargame models that I played with but I have not done a lot of wargamming lately for several reasons. Something I have discovered or re-discovered is board level electronics.  This is due to my decision to buy some Arduino units.  So my love for kits, and building has brought me to look at different DIY projects for mildly usable lab equipment.  The idea here is that I would like to basically build kits, or projects that are reasonably vetted units that I can put together and someday MAYBE if I find a need for it use if the opportunity arises, even if that is just tinkering with things for no other reason than to do it.  I figure if I have access to it I will find reasons to use it, and if I find reasons to use it I may decide to upgrade it later of course, but I would like something that is at least usable for medium duty projects. That is to say, I am not attempting to do groundbreaking work on anything, or even work professionally on anything with these kits but MIGHT use them to fix something I own some day, but otherwise will just be hobby level relaxation type .... toys?

Anyways this brought me to signal generators, I already have ordered an oscilloscope kit, again nothing I expect to be professional grade or anything.  But I wanted to be able to play around with it with a signal generator and started to look into those.  I have looked on eBay and found two separate units.

http://www.ebay.com/itm/301725400862?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT
This has the upside of a sort of enclosure built for it that I can use to give a nice front panel to a full enclosure with a little work.  I belive this unit has a range of 0-200KHz with no MHz abilities at all. I have not found reviews on youtube yet for these.

http://www.ebay.com/itm/361307474492?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT
I believe this unit will be harder to encase, but it seems like it has a wider range of generation abilities. And has a dedicated Digital output for 1,2,4,8Mhz square signals  Although I don't know how much I will need/use that.  Also some reviews have showed these units to be VERY noisy when looked at closely.

I also looked at a more commercial version of a signal generator, and found
http://www.ebay.com/itm/MHS-5200A-6MHz-200MSa-s-Arbitrary-Waveform-Digital-Signal-Source-Generator-2D9S-/311433450337?hash=item4882e15361
This one has some flaws but I was able to find a guy who made a video that fixes a lot of the signal noise by replacing a few of the on-board components, including one of the opamps and the filter.

This one has the upshot of being a half way descent unit (at least verifiable as far as I was able to do in several hours of research into this) as well as being fully built with enclosure.  BUT that negates the upshot of being a kit to build and turns it more into a product to repair.  It is also more expensive than the other two options, as well as a cost to get the parts to fix the signal noise issues.

Another unit I found that has the upshot of being both a kit and a very polished looking commercial unit is this one
http://www.ebay.com/itm/261114462307
This is much more expensive but gives me all my options plus seems to have a good frequency and amplitude spread.  It would cost me around 100usd but would be capable of up to 10Mhz default sine/triangle/square but with the usb seems it is able to possibly do more.

Anyways I hoped to turn to the great community here to see if anyone had ideas on one of those kits over the other, or just not worry about a kit, and go with the commercial product to fix then play with or if there were some other projects/kits out there that I could build that would be better.  I am not looking to spend more than 50usd atm so if I can do it for around that great, if not then I will shoot for saving.  Like I said in the beginning it is more of a working model to build, but would still like to be able to use it for light to medium duty work in the future with computers, rf signals, other consumer electronics, and Arduino type projects.  Whatever I find to tinker with in the future...  Any thoughts?

Thanks in advance for your time and patience with all of us nubs... it is greatly appreciated, it is always nice to know of supportive communities that are so often willing to help others in the pursuit in the  betterment of there own knowledge and intellect.

[Cliff Matthews]

Welcome fellow IT guy! - AD9833 and AD9850 are some searches you'll want to do, since many postings revel in the use of part numbers.
My background is similar to yours, but I hail from the days of the Token-ring and the Big Iron 3033 and 3084 mainframes.

[MrWizerd]

Thanks for the welcome, I will do some more research as I believe my budget for toys is blown this month.  Believe it or not, I started as a computer technician back in '94 when I was 14 the summer before my freshman year.  I was working full time as the lead tech in a firm I helped to start (physically not monetarily) the summer before my junior year.  I was a well known tech by graduation and worked on a great many high end (for the time) systems including the first pinnacle Real time Effects Non-Linear video editing deck made by a non fortune 500 company.  There was a two Alpha's two HP's and one other I can't think of and then my unit I designed, I had to ship the 13,000 dollar unit to them for the cert process and it took 3 weeks to get back with there seal of approval.  It was a pretty big accomplishment for me.  The first computer I ever remember touching was an Apple IIe back in '88 (yes I  was I was HOOKED, I tried to get into the lab as often as I could, but they were very strict with there lab, of course back then for an inner city school that lab was expensive, I think that I could do more with a RaspberryPI now than an Apple IIe back then and laugh.  Not just at the power difference but the price.  Anyways I guess I am off topic,  WAY off, but it is not often that I get to reminisce about the "Good ol'days" HAHA  My step son wants me to teach him to be a tech, and the other day asked me what the black thing was on the board next to the power port on the Arduino Sensor Board v5 (it is the jumper to tell the board which power to use) and when I explained the concept of jumpers and how we used to know how to set the settings on boards by the jumpers he just laughed at how stupid it sounded.  I try to teach him to diagnose a problem pull the part and see if you can repair said part but he says, its under warranty  just send it back.  I told him  what if this was the zombie apocalypse (he is obsessed with prepping for and training for the war with zombies after a fashion  and while he has gown out of it some I still hit him with it cause I find it amusing) would you just send it back.  I did not think the argument would work in so far as to get him to listen but it did. 

I really cry seeing all the old computer equipment go to waste I think of how many of those units could just be slightly refurbished and donated to people who could use one for school or something.  Anyways a whole separate topic entirely.  But it is why I have started him on de-soldering and re-soldering parts now because it is a skill he can always use no matter what is going on. These are things that all technicians should know how to do, replace capacitors or resistors, and such and be able to find them when they are bad, know how to repair the problem not just swap the board.  Of course the smaller and smaller these darn parts get the harder and harder it is to do, now a days you need more than a simple pair of helping hands with a magnifier to see stuff you need a microscope, and I have great vision to boot, its slightly frustrating but these cheep microscope USB cams are nice to help see stuff if only to see what the labels on things are.

Have you built any signal generators? or any other kits that you find usefull?  I have also been looking into building an Arduino controlled adjustable bench power supply.  I have found some plans that I am looking to use:

http://www.deeptronic.com/programmable-1-30v-lab-power-suppl/

I have not looked to deep into weather this one will work, I am probably going to build a rather simple unit using a honeywell 24v transformer that I picked up cheap and will make for a descent little power supply though the plans I have found are a little simple I am thinking of adding some surge protection to the circuit in the form of some thermisters and varistors I am not sure I need both, still have to look into it more before I build it.  I have most of the parts, though the diode I don't have I have only the one lower than it and above it and tried to build it with that and It did not work correctly.  I also did not have the correct capacitors but I am also not 100 percent sure that I wired it correctly either unfortunately.  But it is how we learn, research, build, fail, and research some more to do it all over.  Of course I am happy with doing it right the first time but tend to learn a little less that way.

http://makezine.com/projects/0-24-volt-2-amp-bench-top-power-supply/

Good to meet you Cliff, hope your weekend has treated you well.  By the by the first computer I owned was an old 8088 from Perperdine University's library.  My grandfather got it for me and was so proud, it even had the old double height 5.25" 20MB hard drive!  I loved it I dialed into bbs' all over.  Of course this was pre-graphical internet browsing.  Some part of me misses the old 9600 baud modem handshake.  I promptly blew one of the ram chips on the unit running it hard and I guess I overheated them still not sure how, but I then bought an old 386sx board and chip from a guy, still using my old monochrome monitor and video card, after I got my job at the repair shop I upgraded to a 486 board with an AMD 75Mhz processor (the one touted to be equiv to the first Pentium chips)  I have been a die hard user of AMD since, and diamond/ati/amd video cards as well since my first VGA card. I am a fan of the old computers and the old games too, I used to have an old portable tandy pc the one with the keyboard, monitor and everything in that big suitcase unit.  I traded it for washing a car when I was younger, in fact technically that would have been the first computer I owned but it was missing the operating disks and without those it was rather useless (no hard drive in that unit either)  I wish I still had it I saw a really cool hack of one that put a full modern computer in the unit making it heaps lighter in the process.  But I digress.

[ez24]

If you do not care that it is not a kit - I can suggest a Wavetek 145 off of ebay.  They are good quality and you could have good luck in getting a used one (I did).  Look at the "sold" listings to get a value.

[rolycat]

I am probably going to build a rather simple unit using a honeywell 24v transformer that I picked up cheap and will make for a descent little power supply though the plans I have found are a little simple I am thinking of adding some surge protection to the circuit in the form of some thermisters and varistors I am not sure I need both, still have to look into it more before I build it.  I have most of the parts, though the diode I don't have I have only the one lower than it and above it and tried to build it with that and It did not work correctly.  I also did not have the correct capacitors but I am also not 100 percent sure that I wired it correctly either unfortunately.  But it is how we learn, research, build, fail, and research some more to do it all over.  Of course I am happy with doing it right the first time but tend to learn a little less that way.

http://makezine.com/projects/0-24-volt-2-amp-bench-top-power-supply/

That Make magazine article is horrible. It's practically an object lesson in how not to design and construct a power supply.

There's a discussion of it here.

[GreyWoolfe]

"I really cry seeing all the old computer equipment go to waste I think of how many of those units could just be slightly refurbished and donated to people who could use one for school or something.  Anyways a whole separate topic entirely"

Me, too.  Occasionally, an old computer finds its' way to my workbench.  After refurbishment, I pass the word to my circle and we usually find someone deserving, who couldn't afford a computer on their own.  I have even thrown in a printer for a student who couldn't afford either.  When my company decommissioned 7 year old Dell computers and monitors we had deployed, I managed to get my hands on some (we had the OK from management), sold some on and also gave some away.  Beats going into the landfill.

[MrWizerd]

I am probably going to build a rather simple unit using a honeywell 24v transformer that I picked up cheap and will make for a descent little power supply though the plans I have found are a little simple I am thinking of adding some surge protection to the circuit in the form of some thermisters and varistors I am not sure I need both, still have to look into it more before I build it.  I have most of the parts, though the diode I don't have I have only the one lower than it and above it and tried to build it with that and It did not work correctly.  I also did not have the correct capacitors but I am also not 100 percent sure that I wired it correctly either unfortunately.  But it is how we learn, research, build, fail, and research some more to do it all over.  Of course I am happy with doing it right the first time but tend to learn a little less that way.

http://makezine.com/projects/0-24-volt-2-amp-bench-top-power-supply/

That Make magazine article is horrible. It's practically an object lesson in how not to design and construct a power supply.

There's a discussion of it here.

That's funny, I was thinking it was not the greatest, I just didn't want to be rude but I wanted something to tinker with and improve figured it got no more basic than that.

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[MrWizerd]

"I really cry seeing all the old computer equipment go to waste I think of how many of those units could just be slightly refurbished and donated to people who could use one for school or something.  Anyways a whole separate topic entirely"

Me, too.  Occasionally, an old computer finds its' way to my workbench.  After refurbishment, I pass the word to my circle and we usually find someone deserving, who couldn't afford a computer on their own.  I have even thrown in a printer for a student who couldn't afford either.  When my company decommissioned 7 year old Dell computers and monitors we had deployed, I managed to get my hands on some (we had the OK from management), sold some on and also gave some away.  Beats going into the landfill.

That is really cool... I have heard of places setup with 501c3 non profit status who basically recycle computers to give to the less fortunate.  The may not be the greatest computers, but enough to get you online.  I think it would be a neat community project, gather old computers and parts refurbish what can be saved, loss windows if the unit has a valid license attached like a Dell, install open office and your set really no windows license then a free version of Unix with xwindows and open office.  There is no reason to poor anything that runs over one Ghz in a landfill.  The whole project could operate with zero waste. Anything to broke to repair can be stripped of it's usable components (caps, mosfets, etc), and metals plastics and what not sorted and recycled. 

I think you could even sell of parts or use donations to buy things like new backlights for LCD screens and such that we can't get from salvage.  It's a win win for everyone companies get write offs, inner city schools who blew most of there budget on free and reduced meals don't have the money for computers more often than not... Older computers could even be used in some of these schools to be broken down to learn how they work... The possibilities are endless.

I'm on my son's schools advisory board. We approve budgets and such lucky my son's school is amazing and we have money for several full chrome book carts for full class usage, there starting to get them for every student in the sixth grade then work down till all kids have one on their desks.  The pta pours money into this school which is great considering it's a public school but we also see competitive budgets for other schools in the area and it's heartbreaking how much or school has just simply because we have less free and reduced meals to provide.  Well more discretionary funds the title one schools get more money but can almost only use it for meals.  Every class at this school has smart boards with projectors...  sometimes I think it would be do easy to use recycled computers to setup stuff like that somehow... Or use raspberrypi's  to build small chromebook esque computers by just attaching them to the back of LCD monitors...   anyway it's very cool you do that, watching these videos dave makes reading the comments I'm so amazed by the caliber of people here.  Conscientious beings interested interested the betterment of man, refusing impact on our habitats, just all around good people and it gives me hour that someday we as people will come together and do all the hate and fighting it's very... Inspiring.


Cheers

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[Cliff Matthews]

Great to meet you too. My first computer was a 6802 I soldered together in '79 at school (2k ram, 2k rom, a 74138 address selector and a 6821 to scan a hex kbd and run 7-seg LED's). I graduated in '81 and became a tech at Computerland and then moved to our "big apple" (Toronto) to become an assistant mgr at the Radio Shack at the most well known crossroads in Canada (Yonge and Bloor St.) After that I worked about 10 years as a tech in 3 big banks until some call took me overseas. I leave with just one story:
I recall one odd day in IT came years later working for Dialogic. I was on a 6-week course in our Parsippany N.J. head office training center with techs from several countries. Each day was a 10am - 5pm routine except the day we were bought-out by Intel. But no one told us trainee's a thing and the entire building was ours alone. I mean not a security guard or a cleaner in sight in a massive building with labs and practically every instrument known to mankind to fiddle with. We tried calling reception in the main building but no one answered - it seemed everyone lost their head and bolted to the main complex to see the CEO of Intel tell them the company shares they own just tripled. For a while some of us were looking out the windows thinking maybe aliens had snatched everyone away... Ghost town

P.S. I still collect shiny things and call it a hobby.

[MrWizerd]

Wow, you worked at a REAL Radio Shack, one that stocked like, REAL electrical components... not these glorified Cell Phone Sales floors.... I went into radio shack literally the other day and most everything is on clearance accept for AV wiring, cell phones, and accessories, and power supplies.  There is still two chests of components, and some soldering equipment but most of the Arduino stuff is going away as well.  The store did not even have heat shrink tubing.  The one "Radio Shack" we had that was not a corporate store was one run by this old man named Kandarian he sold mostly electrical components and other such stuff for building electronics. He was an old codger when I was 18 and he passed a few years back and of course Kandarian Electronics closed.  It was a sad day, and I am sure that mostly it was a thing for the old man to do with his time, I don't even know if he was making money after eBay became so prominent.  That was of course late 90's early 2000's and he was never very busy anymore not like he was pre eBay but he stayed open... and he was were you went for that kind of stuff and now you go to the internet.  Either way I will move the off topic stuff over to a private chat so that were not WAY out of alignment with the topic.

[tron9000]

P.S. I still collect shiny things and call it a hobby.

...by the power of greyskull! your gonna need some more racking!

[Kleinstein]

The first two DDS generator kits use a µC to make the signal. So they are really low end cheap versions. The second very cheap kit shows quite good how it works. It's Ok for that price, but don't expect to much performance. Especially triangel will not be good at even 10 kHz.
The first set might be a little better quality, as 2,5 MSPS is just a little fast for an old AVR (might be Xmega). In both cases expect some output upset if the frequency is adjusted.

The Units with case seem to be real DDS units. So they are much faster, though not really high quality. The last one seem to be based on a relaively slow DDS Chip, as the faster one don't provide triangel any more. So it's better than the cheap CPU only Kits, but likely not that good.

The two linked voltage regulators are hardly usefull: the LM317 will neither deliver 2 A nor give 0 V except with a short.  A swithed mode regulator is OK to drive a lamp or motor.
The typical low end lab supply is based of 2 OPs (e.g. LM358) and NPN transistors as an darlington emitterfollower. The only strage thing is this rather simple plan is hardly found on the web - just many cheap chinese ones are buid that way.

[MrWizerd]

Right? I have a lot of hobbies and electronics is by FAR my cheapest.  That's saying something, I suppose if you consider colouring a hobby I am not sure I do but when your colouring with pencils costing a Couple bucks each, meh I guess that makes it a hobby.  Though I am not sure today cost is the only metric for a hobby but I must say collectively I probably have to date spent more on pencils than most of the electronics, but if I don't add the multimeter which I have needed for a very long time, or the soldering iron, which I upgraded cause I needed something that worked for other things, it becomes a close thing, of course that includes my cheap used hot air smd rework station can't claim it's for other things, well shrink wrap and Easter basket cellophane aside.  But I color more to relax on occasion it when kids want me to colour with then.  I collect all kinds of stuff, and probably don't have that much stuff for any one hobby all of them conjoined probably add I have a lot of fish tanks from my note dead aquarium farm (coral, freshwater plants and fish) ex-wife smoked or power bill money away for a few months and they came to shut of power with a bill in excess of six grand.  Coral fits fast without circulation, tanks collapsed I hours, the freshwater stuff survived linger but I list all the babies in rapid succession, and before I was able to get everything moved for me it was all gone. So I have a lot of thanks, also wood wielding t tools those are big..   I want to build a CNC mill, I have seen a few different options for that and of looks like my Dremmel will work for a table to sized one, but I still am looking for done that's reasonable accurate without requiring special metal working tools.

Anyways hobbies take space and my wife complains that my stuff takes over the house, I'm a hoarder she says, I tell her I don't keep trash, she points at broken electronics I tell her it's parts haha

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[tron9000]

Right? I have a lot of hobbies and electronics is by FAR my cheapest.  That's saying something, I suppose if you consider colouring a hobby I am not sure I do but when your colouring with pencils costing a Couple bucks each, meh I guess that makes it a hobby...

Anyways hobbies take space and my wife complains that my stuff takes over the house, I'm a hoarder she says, I tell her I don't keep trash, she points at broken electronics I tell her it's parts haha

true words spoken!

Next to going off-roading with the landrover, its definitely my cheapest hobby!