Project: “Generic” USB 5V/500mA Charger Kit

When it comes to power supplies, the standardisation of USB has made it the ubiquitous choice for many mobile and portable devices. As a result, you probably have an abundance of spare USB power supplies to charge or power your devices with … except that maybe you don’t.

The amount of new products that don’t come with power supplies of their own, in order to cut costs, has been rather disappointing and can result in strange compatibility issues such as slow charging (due to incompatible signalling) or instability due to poor power quality.

So maybe you are after a USB power supply … then you come across a DIY kit to build one for just AU$2.35 including postage … is it a good idea to just build one?

The Kit

For this particular kit, there is no zip-lock bag – just a regular plastic bag closed with some adhesive tape.

Inside, there is a casing, although curiously, it seems to have been adapted from a Li-Ion charger design of sorts, claiming 4.2V/500mA in the molding, model JY-500. There is a pre-wound transformer, some capacitors, resistors, diodes, transistors, a bi-colour LED, opto-isolator and USB socket.

The PCB is somewhat rough around the edges, of a fibreglass variety with silkscreen printing on the top. The only identifiers seem to be H15061502, suggesting to me, possibly a design on the 15th June 2015? The drill-holes also seem to have torn the substrate slightly resulting in the white-halo around the holes.

The underside is a solder-masked copper pattern with lacquer, not the easiest type of board to solder to. Isolation between primary and secondary is visible, and seemingly sufficient assuming the kit is properly constructed. Knowing what I’m like, I probably wouldn’t trust myself to do it right …

The kit comes with a double-sided page of information including a schematic, layout and bill-of-materials. It seems that it’s based on a self-oscillating design with a primary and feedback winding, with this oscillation inhibited (?) by feedback from the secondary when a Zener diode indicates over-voltage. The circuit doesn’t have much in the way of output filtering – notably absent are any inductors for a tuned filter … I don’t think this is a great design. There aren’t any fuses on-board either … with the input appearing to be half-wave rectified as well, which wouldn’t make the power company too happy either.

Construction

A quick computation on the number of joints to complete the kit:

USB Connector - 6
LED - 3
3 x Capacitors - 6
2 x Transistors - 6
3 x Diodes - 6
7 x Resistors - 14
Transformer - 6
Wires - 2
Plug Pins - 2
Opto-isolator - 4
Total - 55

Overall, construction is straightforward – populate and solder with everything being through-hole. One little trick that caught me was the white dot next to the optoisolator on the silkscreen – this does not indicate Pin 1. Mounting the opto-isolator in reverse (as I did initially) results in unregulated output of about 15V (!!!) which can damage devices. The other is the LED – which I mounted in reverse. I suspect F indicates flat … but since it’s a bi-colour LED, this just results in inverted colour indication.

The underside of the board – it’s good to make sure there’s no stray scraps of solder or anything bridging primary to secondary for your own safety.

Trim off excess wire and tin the ends. Then using a hefty iron, heat the pins just enough to get solder to take and then solder the wires to the pins. Overheating will result in the pins migrating through the case.

The case snaps together and is secured with a single screw. When constructed, it looks as follows – almost indistinguishable from the cheap and dangerous bricks often found with cheap Chinese equipment. Notice the strange pre-moulded ratings which refer to a Li-Ion charger of some sort.

The USB connector nestles nicely into the side cut-out.

Assuming you left a little excess length on the LED legs, it comes through the casing quite nicely like so.

Testing

Assuming you’ve been able to find an appropriate adapter so that you can plug the unit into mains (the one I used is a cheap one from China), you should test the output with a USB charger doctor that you don’t care too much about. The reason I say this is because if you reversed the optoisolator (as I did initially), you would have an unregulated output of about 15V that could fry attached devices.

Then, in theory, you could probably connect a load onto it and use it. Note how the charger doctor seems to claim my power bank which is charging is drawing 420mA and having a 4.78V output? Well that’s not quite all fine and dandy …

Getting out the heavy test equipment tells us the bigger picture:

When the charger is idle, it consumes about 113mW, which is below the 1W limit, but it’s still about five to ten times greater than most high-quality supplies included with mobile phones today. The high consumption is possibly down to the LED power consumption and the quality of the transformer itself.

The no-load ripple, however, is rather shocking being about 631mV (!!). Most factory chargers don’t put out more than about 120mV under load, so this is high enough potentially to cause malfunctions or stress on components.

Putting my B&K Precision Model 8600 DC-load to work in constant current mode, I found that the voltage collapsed very quickly at 500mA, so dialling it back to 420mA, we can see the voltage waveform rides from about 5.3V down to 3.9V, the measured ripple averaging about 1.445V. This is the sort of output we might expect from a heavy linear brick supply. Not good.

Worse still, it seems the supply could not withstand even that, folding back its output voltage as it warmed up, resulting in reduced power delivery even at 400mA (above).

It seemed to stabilise more at 350mA, sticking to a nearly healthy 5.20V output. But using 3.62W to generate 1.82W output tells us the supply is merely 50% efficient – a far cry from the 80%+ we’re commonly seeing on quality supplies.

Conclusion

While this kit is inexpensive and comes with a nice enclosure, it’s not a kit I would recommend to newcomers, or for those who actually want a decent USB power supply of any sort.

Being a mains-powered device comes with inherent risks in case of incorrect construction. There is a good likelihood of a pop and some magic smoke, but also, in case of incorrect construction, isolation from the mains might not be guaranteed especially if you don’t assemble the case correctly or at all. For newcomers, I’d hazard to say that it’s not worth your life or various hazards to save a few bucks and have the chance to build your own charger … the plug isn’t even the right sort for Australia!

The PCB quality isn’t ideal for easy construction either, and soldering to the power pins requires a decently hefty iron. The isolation of the supplied transformer is not guaranteed either …

While I might sound somewhat negative, what really puts the nail in the coffin is its performance – the standby consumption is “acceptable” but slightly high possibly due to the LED, but the on-load efficiency is poor (50%) and sourcing anywhere more than about 350mA results in excessive ripple and inconsistent performance. It won’t charge anything quickly or smoothly … I’m pretty sure I won’t want my precious USB-powered devices being subjected to such “noisy” power. Not that this level of power is enough for many devices anymore …

That being said, this was what I expected from something advertised as a “500mA” charger – the bare minimum that could even be potentially useful. But it can’t even deliver on that claim … but at least I can say I built it …

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Random: Hailstorm, Floppy Torture, Earpad Repair & Creative Racking feat. GS724Tv3

It’s rarely the case I don’t get a chance to post until the very end of the weekend, but this week has been one of those weeks. Busyness knows no bounds, made worse when you get some surprise events thrown in your way …

Sydney Hailstorms

Thursday night (14th March) was certainly a night to remember, as we had not one but three hailstorms pass our house, dropping golf-ball sized hail at decent velocities. It may not have broken any windows (luckily), but it did shred almost every single fly-screen and put dents and holes through my mesh C-band dish.

As the dish had survived at least two other hail-storm events without any visible scars, this was not a just another hailstorm – this one was serious causing a fair amount of damage across Sydney. That being said, some areas were lucky, escaping with just rain.

Even rain was not normal, as over the next few days we had heavy, sustained rain at levels causing flooding and breaking monthly averages within the space of a day.

As a result, I spent quite a bit of time replacing fly-screen to make sure the pesky mozzies don’t get in – especially with all the rain we’ve been having. The process is quite simple – but if you’re doing it on your own, the most difficult part is probably maintaining some tension in the screen while you roll the spline in.

My tip? Get some bulldog clips – they can help hold the tension on the screen and don’t “release” when you drop the frame to the ground like clothes pegs might. They also have a fairly low profile, so don’t get in the way of rolling the spline much. I normally use four clips – one on each corner, trim down the screen and then undo the clip on the corner that I start on, roll the spline in, and then when approaching the next corner, remove the clip when you’re about 5cm out. This way you prevent over-tensioning the screen and having “wobbly” alignment.

We had some left-over stock of flyscreen, so I did as much as I could, but that wasn’t even half of the affected windows. I’ll have to restock on the screen and continue the job sometime later …

But that being said, given my C-band dish was already somewhat marginal on gain prior to the hailstorm, I think this may well push the dish into “scrap”, at least for the purposes of feed hunting. At least the panels aren’t tearing out … yet.

Floppy Disk Torture

Last week, I was the recipient of a rusted and face-plate-less Panasonic 3.5″ floppy drive. Having plenty of stock of fresh Sony MPF920s, I decided that I could probably do without this drive, so I thought to myself – how long do floppy disks last?

Maybe I should qualify the question a little more by noting that floppy drives are a “contact” read/write medium where the head rides on the disk itself, wearing away the surface and the head of the drive. Whenever a disk is inserted, the heads are “loaded on” the flexible magnetic disk. As a result, most floppy drives and controllers only enable the motor when reading or writing, so as to minimise unnecessary wear.

So, how long does the disk last? And, on a related note, how long does the drive last? On a check of the spec-sheet, it seems an MTBF of 300,000 hours is standard for this model of floppy drive but others claim a more realistic 30,000 hours. The MTTF ranges from about 15,000 to 30,000 hours. Some spec-sheets also claim that a disk can handle 3-million passes on a single track.

I’m somehow skeptical of the figures. Perhaps they can be achieved in an ideal world, but what about a drive with perhaps slightly dirty/scuffed heads and some “late model” floppy disks which are perhaps slightly lower quality? What happens then? The one thing I didn’t see in the lifetime was duty cycle – the lifetime is certainly not calculated assuming the drive is being used 24/7 – the lifetime is based on power-on-hours. As a result, I suspect they have a duty cycle of perhaps 5%, thus 1,500 hours or so of head-life is my expectation (~2 months).

But if the figure for a disk is correct, 3-million passes would be about 6.94 days of spinning at 300rpm. That’s more than plenty for most uses for floppy disks … but if you had a stuck-on motor … that isn’t hard to achieve on a system that’s regularly powered on. Another thing to consider is that many floppy disks have internal “sleeves” that clean the media and also cause friction with the surface – would this wear down the disk even quicker?

So without much of a real aim except wanton destruction, I set out to test it out and see what happens to a fresh Imation late-model floppy disk that’s kept spinning in an old Panasonic drive. I jumpered the drive select, motor enable and side-1 pins to ground so as to have the drive running, powered it from a Manson HCS-3102 power supply and connected the index and data lines to 1k pull-up resistors and into the Rohde & Schwarz RTM3004. I tried to look at the raw data stream but it is just a series of fixed length pulses with variable spacing – its alignment is notably “jittery” due to the real analog nature of the system, so instead, I decided to go with an FFT view to see the actual signal. On my desktop, I set up a looping wget job to pull screenshots at a fixed interval of 10s from the oscilloscope over LAN.

Perhaps my settings should have had a slightly wider bandwidth and higher sampling rate, but here, we can just see the three bands corresponding to the MFM modulation at 500kbit/s – namely one at 500kHz, one at 1MHz, and one at 1.5MHz. The experiment was started just before 7pm on 11th March.

I don’t know about you, but sleeping with a floppy drive going “shick-shick-shick-shick-shick” is rather therapeutic … that is, until the power supply fan kicks in. Initially, things were all good – the drive was pretty much on-speed and the resulting bands were stable (for an analog mechanical device anyway).

However, about 11 hours later, or about 200,000 revolutions in, trouble started to occur. The drive current consumption started to increase slightly, a sign of increased friction in the system. The drive also started to have spindle speed deviations – it was trying to maintain stability but having some difficulty. At this point, because I wasn’t actually looking at the data stream itself, there may have already been read-errors starting to creep in.

Not wanting to cut the experiment short, I let it go for about four and a half days … but by then, it was clear the drive was struggling. Motor current seemed to increase further until the drive started to squeak and then the motor speed was very much off, rotating at nearly half speed for some time before returning back to full speed just for a short moment and then repeating the cycle.

I’m not sure if this was because the drive motor was overheating or something else was the cause, but the heat could have contributed to case warpage and this could have increased friction on the disk. The squeaking was probably from oxide accumulation on the head, although the FFT amplitude and background noise didn’t seem to change much which was a little surprising given the advanced stage of its ailment.

Leaving it for a little while longer, the motor finally developed enough torque that the “button” that goes into the spindle slot pulled out, disconnecting the motor from the disk for a revolution or two before re-engaging, resulting in the familiar “schlick-clack” sound. The disk was toast and the heads … probably not much better.

So how did the disk fare? Not well. It’s clear that oxide had been cleared off a path corresponding to Track 0 and its neighbouring tracks due to the shape of the head. A few concentric score-lines were also visible due to possible dirt-accumulation on the inner liner.

The wear seemed to be worse on the underside, as the top side did not seem to have the oxide torn up. This may be due to head geometry and shape, but a new interesting pattern to the disk emerged – concentric rings were the surface seems to have been unevenly worn. This may be due to the liner material. A radial pattern was also beginning to take shape – was this to do with the substrate itself or its manufacturing? I’ve not seen this before.

Being a newer, cheaper floppy disk, the cleaning liner only exists on a small wedge, rather than the full inner surface. It has notably become discoloured, especially along the ribs which exert pressure towards the donut, collecting oxide.

So I suppose now I know – keeping floppy disks spinning is a bad idea, with the later disks probably only good for about 11-hours of spinning. Drives are a bit more durable … but head clogs are never a good thing. That being said, the rotational speed may betray the health of the disk surface and head even before any failure occurs – I wonder if timing the index pulses was ever used as a measure of disk health?

But hey … destruction is fun … *throws the lot into the bin*. Maybe next time, I would better do it with some software on the computer so that I would check for data integrity on the disk.

More Audio-Technica Earpad Annoyances

I’ve written in the past about repairing the earpads on my ATH-ANC9, and my recent bad luck with Cowin products, so I’ve reverted to my pair of ANC9s I bought on my holiday to Japan to replace a pair that failed on the way. This time, the earpads on these ones decided to go … but not subtly.

The day before, I put them back in their case and they were fine … today, I take them out and it’s totally blown a seam – more than half-way around. This makes a neat repair a little more difficult. I immediately bought some super-glue to attempt a repair.

Securing the ends, and then securing sections at a time, I was able to get a neat beginning to the repair …

… but then at the top, it was a bit difficult to get the front and back to line up well, so it was a little unsmooth. But it’s still better than a failing ear-cushion! At least it’s as comfortable as before with no risk of falling to bits – but I’m on notice for further tearing, especially on the other ear cushion that’s still okay.

Field-Day Haul – Netgear GS724Tv3 24-port Smart-Switch

The thing I paid the most for at the recent Wyong Field-Day was a Netgear GS724Tv3 24-port smart switch. Readers may have been aware of my use of VLANs in the home through dumb switches and my testing of a low-cost smart-switch with rather hilarious flaws, so I was hoping to get something a little more serious. That being said, buying old networking equipment from a boot-sale isn’t exactly what I’d recommend – you never know (given the few minutes you have to inspect and pay for it) whether if it’s working or not, whether it has any strange configurations pre-loaded, or whether it’s been used in an arduous corporate environment. Regardless, I thought $50 was a fair price to pay to gamble even with the body scratches – after all, the low-cost 5-port unit cost me almost $40.

After I got it home, I cracked it open by undoing the screws and taking the front panel off, followed by the main body cover. Visual inspection proves that aside from a small dead cockroach inside, the circuitry looked okay with rather large heatsinks and thermal-pad connection to the chassis. All capacitors looked to be decent quality Nichicon/Nippon Chemi-Con/Rubycon capacitors with the exception of one L-Tec that was as a DC-input filter from the switching power supply … so was not under much stress. There was no bulged capacitors, so I think it’s probably fine to redeploy.

Powering it up, it takes just short of a minute to come online. Plugging in my configuration netbook with their “SmartControlCenter” software installed, it was easily identified on 192.168.0.239 with “defaulted” settings and firmware that was way out of date.

I was able to login to the web admin with no trouble once I set myself onto the same subnet. Before fully commissioning, I tested every port and found them all to be operational at gigabit rates – then I upgraded the firmware to the latest version. Then I set about seeing what it was like to live with, security wise …

I was somewhat dismayed that Netgear would use HTTP configuration that sent the login information in plain text. That’s not great, but at least the switch does offer HTTPS as an option – but it needs to have a certificate uploaded to it first. Configuration is awfully slow, but at least it didn’t seem trivial to crash. SmartControlCenter uses broadcast to discover the switch as well … which is not ideal.

PORT      STATE SERVICE         VERSION
80/tcp    open  http            Netgear GS724T http config
| http-methods: 
|_  Supported Methods: HEAD GET OPTIONS
|_http-server-header: Web Server
|_http-title: NETGEAR GS724T
4242/tcp  open  vrml-multi-use?
60000/tcp open  telnet          Broadcom FASTPATH Switching telnetd
161/udp  open          snmp            Broadcom Corporation SNMPv3 server
| snmp-info: 
|   enterprise: Broadcom Corporation
|   engineIDFormat: mac
|   engineIDData: 20:4e:7f:xx:xx:xx
|   snmpEngineBoots: 0
|_  snmpEngineTime: 9m09s
Device type: switch
Running: eCosCentric eCos 2.X, HP embedded, Netgear embedded
OS CPE: cpe:/o:ecoscentric:ecos:2.0
OS details: HP ProCurve 1810G, or Netgear GS108v2, GS110TP, GS716T, or GS724TP switch (eCos 2.0)
TCP Sequence Prediction: Difficulty=253 (Good luck!)
IP ID Sequence Generation: Incremental
Service Info: Device: switch; CPE: cpe:/h:netgear:gs724t

I did a thorough nmap scan to find a few strange results – port 4242 seems to be used by their Java device viewer feature which doesn’t work anymore on modern browsers as the Java plugin is depreciated. Port 6000 is used by the Broadcom CLI telnet server … something I wasn’t expecting.

Connecting to it seems to provide a message asking you to wait … but if you wait, absolutely nothing happens. Well, ain’t that a bummer – but it’s because it’s a login prompt in disguise – thanks to this page I was able to work it out. Login with admin and your password … and you get this …

Then, in order to use the CLI, you have to enable it – but it wants a password. Putting in my own password didn’t work – the password is blank – so just hit return.

Then we’re in to the CLI which is apparently partially broken. But now I know it’s powered by the BCM53314. Since I’ve disabled SNMP on the switch, I found it strange it’s still advertised as a service – but it probably isn’t responding to requests, so that’s (perhaps) okay.

Looking around for CVEs, I found this advisory which was worth a bit of a chuckle – the unit was (with older firmware) exposing admin passwords (encoded) through the configuration backup URL which was accessible without logging in, and crashing the switch was as simple as requesting /filesystem/ via HTTP without logging in.

I decided to see what would happen if I tried it – it didn’t break without logging in, so that was nice. But requesting /filesystem/ after logging in still crashes the ability to configure the switch needing a hard power cycle to recover. So half-arsed fixes it is!

Knowing this, I felt confident that I could deploy it in my network – it’s not like my network is filled with attackers and it seems to do the job just fine. The problem is that a large switch like this is not something you just dump on a table-top, especially not on a small table like mine. I don’t have any proper rack infrastructure and I’m not buying any IKEA furniture to hack one up either

Instead, I thought vertically, by unscrewing and reconfiguring the rack mounting “ears” so as to be rotated at 90 degrees, I could mount it underneath my “student desk” on the rear panel so it takes absolutely no desk space.

The gap in the panels is enough to fit the TDK subwoofer upside down, which is nice. In theremaining back-panel space, I mounted my Asus Tinkerboard which does logging and tunnel duties, the Raspberry Pi B+ which does my RasPBX, the Fingbox with its Fing-shell and my open-frame XP-Power 5V/8A supply that runs the three along with a green cable which leads to an ESP8266 weather display on my desktop. All of this, underneath the table with my tower on the right and (one of) my microserver(s) on the left … racing pedals in the middle. That’s space-efficient!

Conclusion

It’s been a busy weekend of random-stuff … but I’m sure there’s more stuff to come when the time permits. The hail storm was a bit of an unwelcome variation to my routine, as was the flaky Audio-Technica ATH-ANC9 earpads … but at least I managed to torture a floppy disk and get my network up and running on the second-hand smart-switch and have it placed somewhere that doesn’t get in my way.

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Project: “Generic” CD4060 SMD Musical LED Fancy Lantern Kit

I have a drawer full of cheap kits and I’m on a mission to empty it! This time, I’m looking at a “generic” CD4060 SMD “musical” LED fancy lantern kit which was purchased for AU$2.89 including postage. What’s so fancy about a few LEDs, I wonder?

The big difference is that this kit advertises its SMD nature – I suppose this is a challenge that might appeal to some … maybe good practice or experimentation for those new to SMD (like myself).

The Kit

We’re back to zip-lock-bag goodness …

Inside, we get the PCB, three-sets of four LEDs, a few diodes and transistors, a capacitor, a switch, potentiometer, speaker, IC, chip-on-board and SMD resistors.

The board is single-sided but covered in silkscreen and solder-resist on both sides. On the top, it’s marked HY 1H34595A.

The circuit itself is single-sided, with the traces finished in tin plate. The tracks are thick in some places and are not soldering optimised, with the soldermask defining the edges of the donuts instead. Despite the sparse soldermask markings and lack of instructions, it is still possible to determine the connections by a process of elimination.

A chip-on-board assembly is provided with a gob top. This is marked with YX015A, although its pin-out is unclear. From what I can tell, this is probably a clone of the CL9300A.

Construction

We begin with a quick computation of the number of joints necessary to complete the kit:

12 LEDs - 24
16 Resistors - 32
CD4060 - 16
4 Transistors - 12
4 Diodes - 8
Speaker - 2
Switch - 6
Trimpot - 3
Power - 2
Chip-on-Board - 5
TOTAL - 110 joints

As this kit is SMD-based, construction starts differently. Not having any solder-paste or stencils, I decided to pre-tin the pads for the resistors first.

This was not a good idea – in fact, I got too much solder onto the pads, resulting in this rather ugly looking result when I used tweezers to place each resistor and run over it with a hot air gun.

Resistors were skewed everywhere, but at least, electrically they make contact. The next step for me was to install the CD4060. Since the pin pitch is not too narrow, I decided to solder this by hand instead.

With a steady hand and a slight excess of solder, I managed to get it onto the board in a decent way.

Finally, all the through-hole components can then go in and get soldered down – nothing too fancy about this, although I left the chip-on-board to the last step.

At this point, we need to install U2, the chip-on-board module. At this point, you should probably stop following the instructions as this is where things start to go wrong.

It was my assumption given the “slot” shape in the board and the fact the card slides neatly and snugly into it, that we are expected to mount the card in alignment with the traces underneath and solder into place.

As a result, that is exactly what I did …

Through careful placement of “fillets” of solder, it was possible to connect the pattern on the PCB to the card without the use of wires.

In retrospect, I should have probably paid more attention to the patterns, as it becomes clear that this arrangement shorts Vcc to a number of the pins … resulting in bad results!

In the end, there was one spare 10k resistor. The lack of spare SMD resistors for other values is definitely not optimal, as they can easily “ping” across the room, never to be found again. No header-pins or connection blocks were supplied for the power input – so you’ll need to solder your own in.

Running the Kit

I applied 5V to the kit and to my surprise, within a matter of seconds, I heard a pop and let out some magic smoke. It seems the music module and the associated 9013 transistor was toast – the way I had connected the module shorted its base to Vcc which led to sufficient current flow to kill the 9013. I suspect the output of the chip-on-board was also shorted to Vcc resulting in its demise as well.

This was all because I took the assumption that the board would go through the slot and connecting corresponding pads would be sufficient to make it work. On closer examination, it doesn’t because the patterns together would short certain elements out. Had I taken the time to trace the schematic out, I would have realised this and perhaps saved the module.

It may have also been further exacerbated by the fact there was no indication as to supply voltage – other sources seem to claim 3V to be the intended supply and 5V may have been a little much for it too.

Regardless, I am left with a kit which flashes banks of four LEDs in a particular binary pattern … the CD4060 part still continues to work.

It was at this point that I traced the schematic out to find that there is no reverse polarity protection for the design (the diode is in the wrong place for that), the music module operates in parallel and independently of the light show (needing just three connections – two for power and one to drive the base of the transistor), and the CD4060 is just driving the LED transistors with three outputs from its self-resetting ripple counter clocked by an R-C circuit. Nothing too spectacular there.

Conclusion

Unfortunately, this kit is the first example in the series of kits I’ve built where a lack of instructions has led to assumptions that let out the magic smoke. As a result, the “musical” LED fancy lantern of mine … is no longer musical and I feel a little sad that I was the cause smoke liberation. After all, my house is a no smoking zone.

That being said, once I drew the schematic and understood what was happening, the kit itself proved to be rather uninspiringly simple. In fact, the music module is “separate” and runs in parallel with no interaction to the light display. The light display uses the CD4060 as a self-resetting counter, with three counter bits driving three banks of four LEDs based on an R-C controlled cycle time.

Aside from that, the PCB itself was of a very average single-sided design, manufactured with decent quality. Perhaps the SMD resistor and CD4060 part of the kit makes for their own challenges which makes this a worthwhile kit to attempt for that reason alone, along with the low price. But in the end, I suppose the lack of music isn’t so bad – it’s probably rather dreadful “noise” anyway, coming from a buzzer-speaker … as a result, I don’t feel it necessary to get another and try again.

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