Archive for February, 2016

Project: Converting a PC power supply to a bench power supply

Sunday, February 14th, 2016

So this will be an ongoing project.

I used to have some old PCs sitting in my closet. They take up a lot of space, and they’re heavy. So on a whim (as it always is), I decided to gut the PCs.

One of them, apparently I had already removed the power supply, so it was gone (if I remember, it was quite noisy, so no loss). The other still had its PSU, so I’ve selected it as the donor to my bench-top power supply project.

psu2

psu1

The PSU is effectively a 450 watt supply, more than enough for my needs. Also it’s one of the older supplies, so it appears to have a -5V wire (most modern supplies don’t have these anymore).

Reference

Here’s a video breakdown of ATX power supplies that seems quite informative.

http://www.instructables.com/id/ATX–%3E-Lab-Bench-Power-Supply-Conversion/?ALLSTEPS

http://www.instructables.com/id/A-Makers-Guide-to-ATX-Power-Supplies/?ALLSTEPS

Parts

I’m going to need parts. Banana plug sockets and some large resistors.

Something I’m thinking about doing is making one of these.

Sick of Beige basic case

Ultimately the goal is to make an all in one, but I’m tempted to try building an external board you can plug an unmodified power supply in to.

I’m going to steal connectors and things from a couple obsolete motherboards. I’m never going to use these computers again anyway, so why not put them to good use (instead of the trash).

Research: Value Oscilloscopes

Sunday, February 14th, 2016

So basically, this entire series of tool research posts is the result of me searching for an Oscilloscope, and then discovering my existing workflow was bad.

I’ve lost count at how many hours I’ve spent doing homework on low cost high value scopes. I’ve explored a variety of offerings from Siglent, Rigol, Owon, Uni-T, Hantek, and others, trying to find the best value. I don’t have the desk space for an old analog scope (which is a way to get a good scope for under $100). So I need a smaller digital scope to fit my setup.

I’ve tried to give each brand a fair shake, but in the end, all signs point to one.

Rigol DS1054Z

Cost: $399 US

rigol

Pros
– 4 Channels (Bonus!)
– 50 MHz (software upgradable to 100 MHz)
– Integrated Help
– Pretty much everything you want
– Small
– Low price (given what it can do)

Cons
– One set of knobs shared amongst each channel (versus separate knobs per channel)
– Fan could be quieter
– Not-so-great FFT (no substitute for a spectrum analyser)
– Many built-in features cost extra *

I’ve mentioned EEVblog several times, a very picky experienced EE, and this is his recommended scope.

After much fuss, too much reading, I can’t seem to find a scope in this price range that does everything as well as this one, and that even ignores the fact that it has 4 channels. You get 4 channels! Everything else in the price range has 2. Madness!

Summary

I’ve accepted there’s no other scope that even comes close. The only reason I haven’t purchased it, is that buying one will cost me about $650 CAD… which is a lot of money. Every non-oscilloscope device I’ve been researching costs under (or around) $100. $650 is a lot.

I’ve actually found cheaper scopes. Amazon.ca has a few Siglent scopes for just over $400 CAD, no tax (roughly $300 USD). I got real close to buying one, but ultimately stopped myself once I realized it wasn’t the latest Siglent model (those cost about $800 base). Then I learned about some of scopes that, for whatever reason, can be hacked to become better scopes.

Actually, I do have an Oscilloscope. A really basic one I picked up in 2009 called the DSO Nano.

crapmeter

I’ve never really used it seriously, but it’s not exactly the most useful oscilloscope. You can buy a DIY kit for about $20 that does basically the same thing.

So yeah, scopes. I know what I want, but now comes convincing myself to spend the money.

Research: Fixing 858D Hot Air Stations and Fake Hakko Irons

Saturday, February 6th, 2016

Researching, I learned that China does make some good Soldering Stations, Hot Air Stations, even some good hybrids.

YIHUA_898D

The problem is they assemble them wrong. VERY WRONG! DANGEROUSLY WRONG!

They don’t always do them wrong, but it’s best to assume it’s wrong.

If you’re up for a challenge, have another iron at your disposal, and are willing to do the homework, you can fix your cheap Chinese Iron. Replacement parts are extremely cheap, so even when things do break down, it wont cost you much to keep it going (or replace it outright).

It’s a project though. IMO, a good one for a hobbyist.

Dave from EEVblog speaks highly of his, but his does appear to be assembled correctly.

This is a video with more than 200,000 views, so it may have sparked increase interest in these cheap Chinese devices. Analysis of more devices shows most of them are incorrectly assembled though.

http://www.eevblog.com/forum/chat/deadly-wiring-fault-atten-858d-hot-air-rework-station/

Above is a thread talking about this. In it, many people discuss the problems they found, with some talk of fixes.

There isn’t a guide for how to fix these. You’ll have to read the thread, research what they’re talking about, and try it.

I’m hoping to find some additional references from folks that fixed theirs.

So far, here’s what I’ve found:

I’m planning to buy one myself. I actually ordered and cancelled a few units from Amazon today, as I learned more about this. Initially I assumed one of the bulkier devices would be more reliable, but I don’t have a lot of space in my “laboratory”. So I’ve decided to research the Chinese models, and find a good 2-in-1 unit, and fix it.

One of the problems ordering the devices from China however is that most of them appear to be 220V. 110V (and 120V) seem to be included in *some* product descriptions, but some of these listings don’t really instil much confidence. I’m using 5 star orders from US/Canadian customers to gauge successes here, but sometimes I can’t find them.

So, this is an ongoing research project of mine. I will probably order one from China instead of Amazon. That way, I have more choice of layout. I’ll make another post once I’ve decided on my unit.

EDIT: Transformers

This is a very good video that explains how a standard transformer works.

I like that it actually explains the difference between some 110V and 220V transformers… just a simple rewiring.

UPDATE: Decided against 2-in-1

Well my hope was to find a good single device with both features in one. But ultimately I decided to buy separate units.

The reason is because no matter where I looked, nobody seemed to have anything positive to say about the irons in the 2-in-1’s. In fact, I’d come across videos like this where the iron breaks during the video review.

Yikes.

So instead, I’ve decided to try a fake/counterfeit Hakko 936. Hakko being a top quality Japanese maker of Irons.

fakehakko

The 936 is actually an obsolete iron that’s no longer made.

Now, this is not the same thing as the clone Hakko’s.

clonehakko

The clones all have strange company names, the same case and product code, but there are actually a some subtle differences. For one, the connector used by the irons is actually the opposite (female instead of male), so it’s not directly compatible (even though it’s effectively the same).

Now I don’t know if this is actually true, but I get the impression that the fake/counterfeit ones are better made than the clones. At the very least, they appear to try harder to make you think they’re real authentic units, from the quality of the packaging, to the English manuals and data sheets they include. I’ve yet to find a good teardown/unboxing of the fakes in English, but these Russian ones do fine.

Of course, when I say “better made”, it’s a loose suggestion. I still wouldn’t trust plugging in the devices without tearing them open first. But it’s all about the little things they appear to do in the fakes unlike the clones to convince you they’re authentic.

Not to mention, you can cheaply buy replacement parts for everything, from the irons, the heating elements, even the sockets and main board.

hakkoboard

You could literally build one from parts.

So this is why I decided to go with a fake Hakko, for the repair-ability. My unit comes with a spare heating element, but I also ordered a spare iron, spare board, and spare connector. $10 in parts that should let me correct any issue that crop up with this $40 iron (I still have my junky old Weller iron as a backup to do said repairs). Really, the only thing I’m missing is a spare transformer and case. 😉

As for the standalone SMD Station (hot air gun), I actually bought one off Amazon. It’s totally one of the same cheap ones you get off AliExpress, but frankly price wasn’t any better if I was to order direct.

smdstation

Despite the photo, I’m not entirely sure the unit has those memory recall buttons. The Amazon page has variants with and without, and people that own them have suggested theirs did not have the buttons. TBD.

Also the other problem, Chinese new year. It’s ongoing these next few weeks, and it’s going to add a HUGE delay to the already slow shipping (normally a month+). The SMD Station is warehoused at Amazon, and should be here Tuesday. IMO I actually need the SMD Station more. I currently have no way to shrink heat-shrink-tubing (aside from a book of matches). So I’m looking forward to that so I can start doing scientific things with heat.

Since this a standard Chinese unit, I grabbed a replacement heater from China as well.

Unfortunately I don’t have a way to correctly measure/calibrate temperature, so I’m just going to have to guess for now. I did order a cheap temperature gun sometime ago (hopefully showing up soon), but an actual heat probe would be much better here. None of my meters have temperature probes.

Anyway, that’s that. Now we wait.

Research: Value Bench Power Supply?

Tuesday, February 2nd, 2016

I dabble with micro-sized computers. Things like this.

Orange_Pi_One_Large

The device above is something called the Orange Pi One, a cheap Chinese designed and manufactured board. Costs about $10 + shipping (~$4 to Canada).

Unlike the highly regarded Raspberry Pi Zero, it has a Quad Core ARMv7 CPU (vs. a single core ARMv6, slooow), a full sized HDMI, full sized USB, and an Ethernet Jack. Pretty amazing little machine for a tenner.

The Orange Pi boards have 2 things that make them slightly troublesome.

  1. Software support isn’t great. The AllWinner H3 lacks mainline support in the Linux Kernel, but it is getting better. Maybe by the end of the year.
  2. It doesn’t use the “standard” Micro USB port as a power connector.

The power supply part is unfortunate, but there is a workaround: The device CAN be powered via the expansion header.

Most of these tiny boards require 5v 2A to get the most out of them. Many modern cellphone chargers do meet this spec. I could just sacrifice one of those, chopping off the end and soldering pin headers in their place (I probably should, as this is common enough). I went down a different path though.

Bench Power Supplies

Any true electrical engineer has a true bench power supply. Unfortunately, a good one tends to cost hundreds of dollars.

The high-quality budget alternative tends to be converting an old PC power supply in to a bench power supply.

004

This makes a lot of sense, since PCs are already quite sensitive to voltages, so extra care is already taken by good PC Power Supply manufacturers to make reliable units. That, and the pins on the ATX connector are already the common voltages that most things need.

Sick of Beige basic case

Alternatively, you make or buy a simple daughter-board that takes an ATX connector, and gives you the desired outputs.

That said, the right of passage of any hobby electrical engineer seems to be making your own bench-top power supply out of an old PC power supply. Some day I’d like to do this, but not today.

“Buy an old used one instead”

hvps01

I’ll admit that’s kinda cool, but at the same time unwieldy and large. I don’t have a dedicated workbench. I do this so infrequently, that I have my office desk I work on. I keep some ancient hardware around (Commodore 64, retro game consoles), but for the most part I prefer newer technology.

I like portable. I do most of my work on a laptop.

Despite the reputation of cheap sub $100 power supplies, I wanted to be 100% sure that they were “all crap”, as everyone says.

I hate being told absolutes without evidence, so I checked the evidence.

MCH K305D

Cost: ~$60

mchpsu

This was the first PSU I found that really got me excited. I love how tiny and small it is. And the price… well, at the time I accepted that $60 would be an acceptable price to pay.

Alas, looks can be deceiving, and a deep dive reveals what’s inside is a bit of a nightmare.

Such a shame. It’s petite, and not bad looking. Functional (?) but scary.

KSP 305D

Cost: ~$60

305d2

Here’s another small one like the MCH above. It has a 2nd set of knobs for fine control (I’ve heard this is a recommended feature), but only 2 lines to tap (no earth ground).

The problem with this one though…

…it doesn’t exist.

Now, don’t get me wrong. It sort-of exists, but I can’t for the life of me find a photograph of the internals. I can find plenty of external shots. I can find dozens of alternative product codes (KSP303D, KSP605D, etc), models with different connectors, but apparently nobody owns one.

The Flat One: CPS-3205

Cost: ~$60

gophert

Instead of being tall, here’s a flat one. Of the power supplies mentioned so far, this may actually be the best so far, but it’s not without it’s problems.

It’s the first one that is able to safely power on without spiking, but Dude in the video above does actually manage to make it spike, under certain conditions. The video is a bit slow getting to this, but this does worry me that spikes may be inevitable in this cheap gear. I want to come back to this video sometime so I can hopefully better understand what he did to spike it.

It’s worth mentioning that the spikes appear to only be double the current, so a compromise appears to be setting the initial levels lower, then raising it.

Unfortunately, due to the clumsy user interface, this device requires a bunch of clicking and mode switching to change the levels.

If only there was a device that could be cleanly powered on with per level control?

The Anomaly: UNI-T UTP305

Cost: ~$90

unitwoo

Hey! UNI-T is back with a slick little unit using their lovely black and red theme.

The asking price is about $30 more than the above units, and amazingly, it may actually be worth it.

In the video above dude was unable to make it spike at all. This seems impossible for a sub $100 device, but lo and behold.

Now, to be fair, he hasn’t done the same extensive number of tests the dude in the CPS-3205 video did. It may still be possible to spike the unit in those same conditions.

The same video author loved his unit so much, he bought a 2nd one.

He also modified it to slow down the internal fan (and thus reduce the noise). I’d be tempted to make the same mod myself, but perhaps on a switch.

Sounds great right?

It does, except for one minor detail.

For some reason, UNI-T doesn’t acknowledge the existence of this device on their website.

http://www.uni-trend.com/en/

I’m sure it’s just an oversight though, but even after digging, they don’t even sell them in their Chinese online store.

However, it is worth noting they do sell a 220v white model, exact same box, different product code for about the same cost. Some stores are listing it as discontinued, so this new red box with the switchable AC voltage is probably the new model. Not to mention, it looks way cooler in Red+Black.

Summary

UNI-T comes through again. In my research of other UNI-T devices, I found that they appear to do everything safely, but cut back in areas of little consequence (connectors that could wear out/need repairing, simulating automatic hold by using a 6 second timer). Their compromises don’t seem dangerous like the bargain models above, but I would strongly avoid pushing the limits of their devices.

I’m very tempted to grab the UNI-T device. While a modified PC power supply will do the job, I’d really like to have something that can limit the current. Maybe it’s a minor point, but that to me seems like something to have. Paired with a modified PC power supply for the big current draws, you could probably do most power work.

Tempting. Very tempting.