Bootleg Battery Charger Heart Transplant

Following on from my previous post where I looked inside a cheapo battery charger from eBay – I have since gutted the charger. All that I kept was the case and the battery contacts.

Gutting the unit eliminates a potential fire hazard. I replaced the circuitry with a dedicated lithium ion battery charger IC instead.

I’m using a MAX1555 and it is a single chip solution which requires a minimal number of external components. It is a single cell charger and has a maximum charge current of 280mA.

The chip has dual inputs, allowing you charge a battery from either a USB port or a DC plug pack. When charging from a USB port, the charge current is limited to 100mA. Whereas, the DC plug pack input allows for a charging current of 280mA. Also, this version of chip has a charge status indicator which can be used to drive an LED.

I’m not going to use the 240VAC socket anymore, and I’ve replaced it with a micro USB socket. This change lets me use a USB wall socket adapter which can deliver 1500mA at 5VDC. However, my new circuit will only require 280mA. (I’m already thinking about a 2nd iteration of this project which will use an IC with a higher charger current to charge faster.)

Schematic for the new battery charger using a MAX1555 IC.

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Bootleg Battery Charger Teardown

Its amazing how cheap some stuff is on eBay these days.

For example, I picked up 3x lithium ion batteries and a charger to suit my Olympus TG-4 camera for $25 Aussie dollars, including free delivery.

I got this charger and 3x batteries (yes, I know, only 1 battery is shown) for about $25. This stuff is just too cheap and nasty.

I have an upcoming camping trip and I wanted to get some spare batteries for the camera.

I didn’t want to buy just 1 battery in case it was dead on arrival so I got 3. The battery charger was a bonus. Olympus don’t supply a proper battery charger when you buy a TG-4, you have to charge the battery in the camera with a USB charger and charge times are pretty slow. Olympus sells an AC powered charger but its about $70 and doesn’t include extra batteries. I was hoping that the new charger would be faster or reasonably good, but I didn’t have high hopes on the quality of the battery charger.

Two screws at the back of the charger were removed, but the plastic halves are ultrasonic welded together. Splitting the ultrasonic weld was very easy though. A bare minimum of plastic has been used and it isn’t very rugged.

It looks pretty crusty.

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Linear CCD Update

Just a quick update. I was going through some boxes that I haven’t unpacked since moving and I found the linear CCD I was experimenting with.

After reviewing some schematics I’d saved and reviewing some datasheets, I’m sort of back up to speed with where I left the project.

I managed to get some traces on my analogue oscilloscope that sort of match the datasheets but the relatively fast timings and the inability to store a trace on my oscilloscope was making things difficult. So, I took the board into work to use one of the good digital oscilloscopes in the workshop and I managed to get the following trace.

Yellow trace is the CCD output signal. Green trace is the transfer gate signal I was using as a trigger signal.

After performing a few tests I am not confident that I have all of the signals or the timing correct. Why I know this is because when I placed small pieces of black tape over the CCD’s lens, I was not seeing a decreases in signal intensity to match the number of pieces of black tape. Also, when I shaded a quarter of the CCD, the signal output for all the CCD’s pixels decreased in output value rather than the pixels that were shaded.

Anyway, I’m learning a few things about analogue electronics which is good. So far I’ve needed to improve my knowledge on op-amp circuits and I’ve been using a sample and hold circuit to help isolate the specific pixel output signal from the entire output waveform.

Anywho, I’m sure I’ll share more details as they arise.

4-20mA Panel Meter Teardown

I haven’t done a teardown in a while so I thought I’d share the insides of panel meter I recently found at a Sunday morning junk market for $5.

Below is a panel meter that has been used in some sort of industrial process. It was manufactured in 1980 by Kuwano. I’m not quite sure who the manufacturer was – the company’s logo is not easy to read but it might say, “Aumano”. What caught my attention with it was that it includes high and low needles as well as indicators and relay outputs for the high and low limits.

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HP5082-7340 Hexadecimal display

Happy New Year everyone. A quick post to get the new year started and I recently scored a few HP5082-7340 hexadecimal LED display chips. These are cool looking integrated hexadecimal LED displays measuring 10mm wide and 14mm high with standard 2.54mm pin spacing.

A great feature of these displays is that each chip contains all the decoder and driver logic internal to the device. Unlike a Texas Instruments TIL302 which requires a BCD to 7-segment display driver chip such as a SN74LS47, the HP5082-7340 requires 5V, 4x pins for a BCD representation of the character, an enable signal and an optional display blanking signal.

Additionally, there is no need for current limiting resistors, this is handled on-chip.

To demonstrate how the display looks, a quick breakout was made, a schematic of the circuit shows the simplicity of interfacing one of these display chips to a microcontroller.

Interfacing an HP5082-7340 hexadecimal display to an Arduino microcontroller

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Printing Heat Shrink Cable Markers with a Dymo Labelmaker

Recently I saw you can buy heatshrink tubing cartridges for Dymo label makers. This would be really convenient to make professional looking markers to identify individual wires and cables in some of my larger projects. (Cable and wire markers for industrial applications such as these have been around for at least a decade now, but are pretty expensive. This solution from Dymo seems to be somewhat more mainstream, but it still is too expensive for the hacker)

However, my hopes were dashed when I realised that the cartridges aren’t compatible with my $35 Dymo LetraTag. Also, each cartridge is $50, so I wasn’t keen on buying one hoping that I could get it to work with my label marker.

So I got thinking about making my own and I managed to cobble together a somewhat effective method using some regular heat shrink and some 180 grit wet & dry sandpaper.

Somewhat successful printed heat shrink cable markers

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Multimeter Accuracy and AD587 Performance

Having built a small, portable 10.000V reference using the Analog Devices AD587 reference chip, now is a good time to evaluate its performance with a bunch of multimeters.

However, I have a feeling that the AD587 with its 10.000V ±5mV @25ºC is going to be the better performer than some of the multimeters being tested. In today’s performance shootout, ranked in order of their pedigree we have:

  • Fluke 789 Processmeter
  • Fluke 12 Multimeter
  • Extech EX330
  • Pro-Tester 03-150K
Today’s contenders. From left to right; Fluke 789, Fluke 12, Extech EX330 and Pro-Test 03-150K.

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Simple Electronics Workshop Tool Rack

Last week I had to have a huge tidy-up of my workspace, things were getting out of control. Finished projects, half completed projects, tools, test wires, components and general junk were just piling up. It was becoming unworkable – things were getting lost, projects forgotten and enjoyment was fading.

Whilst watching YouTube (to avoid the inevitable task of cleaning up), one of those YouTube “Recommended” videos popped up with Adam Savage talking about his workshop. Anyway, in typical Adam Savage fashion, he said a few one-liners. One of them being, “Drawers are where things go to die”, 0:58. I had a laugh at this, thought nothing of it, watched some of his video about his tool stand and stopped watching after about 3 minutes because the whole video is about a tool rack.

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AD587 Battery Powered 10V Reference Tutorial

Following on from a previous post discussing the Analog Devices AD587 precision 10.000V voltage reference, I built a portable device to utilise the chip.

Some requirements of the project were:

  • 10.000V ±5mV output
  • 10mA output
  • Battery operated device
  • Visual, low battery indication
  • Small, aluminium housing
  • Clear front panel
  • Low cost (under $50), readily available components

A low battery indication was a desired feature to prevent the device being used in an important test and the battery level drops low and compromises the AD587’s performance. A simple green LED will suffice. Output performance of 10.000V (± 5mV) couldn’t be compromised so there is no protection to prevent high current draw from the chip, I’ll just have to be sensible.

Battery powered AD587 10V reference.
Battery powered AD587 10V reference.

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