A Minimal Security Small Safe/Lock-box – Caveat Emptor

I live in a safe area with negligible theft. Nonetheless, I recently decided to install a minimal security safe/lock-box – one that will keep certain items from the eyes and fingers of basically honest people that visit my home, such as visiting tradesmen, cleaners or house guests. No safe is theft proof and my need is for a container that would require defacing or damaging it in order to access the interior. Such a safe would not deter a dishonest person but would prevent tempting basically honest visitors. My caveat – I know that the safe that I am about to discuss is useless against a true thief .

The Chinese made small (23 x 17 x 17 cm) electronic safe that I purchased via eBay cost me $18.95 including shipping from California. See Fig 1 & 2, below.

Fig. 1 – EBay Listing

Fig. 2 – Electronic Safe

I was aware of the faults outlined by several YouTube reviews, such as YouTube user mepickulongtime but felt that I could improve its utility and at this price it would be an interesting exercise even if I failed. Most, if not all similar electronic safes that make a mechanical “click” when the correct combination is entered, use a solenoid to temporarily unlock[1] the door. Safes, such as on cruise ships and many hotels, that emit a motor running sound when the correct combination is entered to open or close, do not use a solenoid and are thus secure from a “bump-open, although they do have other vulnerabilities that I won’t discuss here. There are many nearly identical solenoid locked electronic safes. Some are identical and others have mostly cosmetic differences. While several Chinese manufacturers may be copying each other’s products, it is more likely that small “factories”  buy common components and assemblies from the same suppliers and the final safes’s differences are minor and superficial. For example, sellers on alibaba.com sell the entire insides of this type of safe for $3 in quantity 100. See Fig 3, below. Small Chinese shops can build or buy a steel box, insert the safe “guts”, add some cosmetics and bingo – they are a safe manufacturer. BTW – sellers on alibaba sell this entire safe, exactly as I purchased, for as little as $5, in quantity 1,000.

Fig. 3 – wholesale safe “guts”

Fig. 3 – wholesale safe “guts”

The solenoid used in this safe is shown in Fig. 4, below, where I “exploded” it for a better view.

Fig 4. – Exploded View of Solenoid

Ebay’s safes are generic but the branded ones sold by Harbor-Freight, Amazon, Honeywell and others have virtually identical solenoid mechanisms.

I intended to add a couple of the improvements outlined by YouTube user HifiCentret and YouTube user “Ben J”. I felt that HifiCentret’s improvements would elevate this safe’s usefulness.  However, once I discovered significant deficiency I stopped. The metallic looking plastic opening lever actuator (T-Bar) on the front door is a huge security weakness. More on this later in this post.

HifiCentret adds a cowling surrounding the reset button [see video location 3:17]. This only matters if the rear is accessible and since I intended to mount the safe flush to a wall, secured into the wall and sturdy shelving below, so I am not implementing the cowling.
HifiCentret cut a groove around the solenoid’s shaft to catch the bolt assembly during a “bounce open” attempt [4:15]. I have not yet done this, but I may because it is a feasible, reasonable solution.
HifiCentret reduced the gap between the solenoid and the bolt assembly. I have done this and, in my subsequent tests, I feel that it greatly hampers a “bounce open” attempt.[4:50]
HifiCentret strengthened the solenoid spring by stretching it. I have done this and feel that it is effective[5:30]
HifiCentret installed a physical barrier to prevent someone from puncturing the leftmost LED hole and inserting a wire for snaking over to the solenoid to push it down.[5:50] I did not install HifiCentret’s barrier because (1) I am only trying to protect against basically honest people that visit my home who would not deliberately deface the safe, or anything else in my home; (2) I discovered a far more egregious defect that can be exploited by a person that doesn’t mind deliberately defacing the safe, which I’ll discuss next.

The opening lever actuator (T-Bar) of my safe is totally made of plastic, including the shaft that extends into the safe’s cavity. See Fig 5, below. It is secured by a cotter pin. See Fig 6, below. Plastic may have been sufficient if the shaft that penetrated into the safe’s interior was within a steel tube but in my case the plastic shaft passes through a “pinky finger” size hole in the front plate with no protection inside.  “Ben J’s” safe appears to have [1:48] a desirable steel opening lever actuator (T-Bar) with a short shaft. All of the current products that I see advertised today look identical to mine so, possibly, “Ben J’s” safe is of a different vintage or costlier design. Anyway, the flimsy plastic opening lever (T-Bar) on my safe would be easily snapped off with a stout screwdriver. Then, using the same screwdriver, the remaining plastic shaft could be pushed in, leaving a “pinky finger” size hole that would permit a “pinky finger” or tool (how about the same screwdriver) to press down the solenoid. See Figs. 6, 7 and 8, below. The absence of the steel tube surrounding the T-Bar’s shaft and the parts being made of plastic, makes this safe easy to be defeated by anyone willing to deliberately deface and damage the safe. I  consider this safe to be only slightly better than a locked wooden desk drawer – or possibly of a comparable level of security.

Fig 5. – Actuator Handle (T-Bar)

Fig. 6 Actuator Shaft Inside View

Fig. 7 – Actuator shaft Inside View

Fig. 8 - Finger through Large actuator Shaft Hole

Fig. 8 – Finger through Large actuator Shaft Hole

There is more! The metal thicknesses are disappointingly thin.  Actual measurements are shown in the clickable (to enlarge) images below.

 

pinky

The steel bolts, which are robust looking, are flimsily attached by peening to the bolt slide, which itself is only 1.13mm thich. See Fig. 9, below.

Fig. 9 – Peened Bolt Attachment

My last figures aren’t a criticism – I’m showing the electronics board for completeness in Figs 10 & 11, below. The PCB is a single-sided Printed Circuit Board that utilizes an ELAN Microelectronics (Taiwan company)  EM78P153S  One-time programmable 8-bit microprocessor.  Fig. 11 is a reverse-engineered schematic of the board. Note – there could be a slight error somewhere in it as it was done rather hastily.

Fig. 10 – Printed Circuit Board (PCB) Front View

Fig. 11 – PCB Schematic

Bottom Line: This safe is useless against a true thief  but may be of some limited value to keep certain items from the eyes and fingers of basically honest people that visit, such as visiting tradesmen, cleaners or house guests.

  1. Credit: Solenoid mechanism diagram is a link to Jaime Capra’s website that reviews “Best Small Gun Safes”.

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A Good Laser Printer for Linux

A month ago I purchased, via Amazon, a new Brother MFC-L2710DW wireless laser printer/scanner/copier/fax e/w multi-sheet feed and 2-sided printing. Apparently I unknowingly bought it during a big sale because I paid $109 yet the current price is $199. Anyway, it is a great printer that works flawlessly with Linux.  I don’t know why I got 45% off  but if you are interested watch for a sale. You don’t have to pay the MSRP of $199.99 as many websites offer the printer at discounted prices. It is a great printer even if you don’t get 45% off.

I had a perfectly good Brother HL-L2380DW laser printer/scanner/copier/fax BUT it did not do 2-sided copying or have a multi-sheet feeder. It was given to me for free so when my new Brother MFC-L2710DW was delivered by the postman I gave the old HL-L2380DW to him – passing the favor along. He is a beekeeper and needed a printer for his beekeeping workshop.

Brother supplies Linux drivers for all of its printers but, in my case, those drivers are in the Manjaro/arch repository so installation was a breeze on my Manjaro system.
The MFC-L2710DW is much faster than the old HL-L2380DW and I really like it. It handles thicker paper and envelopes easily, as well.
If you need a good Linux-supported laser printer I recommend the Brother MFC-L2710DW

CAVEAT:  The TN760 toner cartridges for the Brother MFC-L2710DW have an embedded Integrated Circuit chip that tracks page count. You’ll see “Don’t buy” warnings from some people because of this. I don’t agree. Personally, I’ve had mixed results with non-OEM toner cartridges but most often I don’t use them primarily because Brother’s toner does not contain fuser oil like most, if not all 3rd part cartridges and toner with fuser oil works poorly for making heat transfer printed circuit board masks. Admittedly, there are new “no heat toner transfer” methods that I have not yet tried and they may work with fuser oil present. If you want to avoid the OEM cartridges just search YouTube for “replace chip of TN760 toner cartridge”. EBay even sells 3rd party TN760 chips in bulk.

BTW: This is an unsolicited endorsement. I have no relationship with Brother – I just like their products and especially their good Linux support.

 

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GeoCoin – My 2nd Electronic geocoin

This is my second electronic GeoCoin using the same electronic design. My first geocoin was one shaped like the state of Florida – see THIS-LINK. This one is in a more traditional geocoin shape. The only thing that it does is blink and LED on the top of the board. It should blink for a minimum of a year using a three volt coin cell. I have it blinking once per minute but the rate can be varied by changing the value of R4 and/or C1 which can be seen in the schematic, which is shown in the video.

This was a prototype and design defects will mandate another version. The diameter is too small to accommodate a larger space to write the tracking number. I may be able to scratch in a tracking number on this board ‘s small space with a sharp point BUT it would be difficult. This is a work in progress. A slow work.

Posted in EDA, Electronics, geocaching, hardware, PCB Design, Uncategorized | Tagged , , , , , | Leave a comment

Repair/Upgrade SANGEAN RCR-5 Clock Radio

I have a SANGEAN RCR-5 Alarm Clock Radio that I use to play its radio each morning at the set alarm time.

RCR-5 SANGEAN

RCR-5 SANGEAN

The RCR-5 radio has excellent audio quality for such a small unit – not tinny at all, with nice bass and treble. I really like this radio because (1) the radio receiver is sensitive and can easily pull in a distant station that I like; (2) when the radio turns on the volume gradually increases until it reaches the maximum that I set for that alarm – I don’t like to be shocked into wakefulness; (3) it has good audio for its size. This radio has many features but one that is important to me is for the time and settings to be preserved through minor power outages. The RCR-5 claims to preserve time and settings through a 10-minute power outage. This is quite inadequate but worked through 90% of the very brief outages common to where I live. Alas, I noticed in recent months that my RCR-5’s backup capability had shrunk to five seconds. Now that was truly worthless! The clock only cost around $30 so sending it back for repair didn’t make sense – I could buy a new one for what repair was likely to cost.

I purchased a replacement (not a RCR-5) and it will soon be returned. It has a sensitive receiver but the audio quality is terrible – quite tinny – like an old 1970s pocket radio. I decided that it was time to attempt a DIY repair on my RCR-5.

After removing four screws the RCR-5 interior was easily accessible. I quickly located the Super-CAP (See Image 1 & 2 below). What an anemic, puny little Super-CAP – why did they bother! It is unmarked and is about 5mm wide and 1.5mm thick. Also, the capacitor appeared to have leaked. Obviously it had failed, which is why the RCR-5’s advertised 10 minute settings/time backup didn’t work. The voltage across the capacitor in situ was zero. I removed the Super-CAP and measured its feed pins and it was 3.1VDC. Apparently, the capacitor was internally shorted.

Image 1

Image 1

Image 2

I had three Super-CAPs left over from and old project and decided to install them into the RCR-5. These Super-CAPS are rated 10 Farads at 2.7V. While they “might” have survived the slightly higher charging voltage I decided to wire two of the 10F capacitors in series, yielding one 5.4V Super-CAP of 5F. I substituted this new SUPER-Super-CAP in place of the defective RCR-5 original. See Image 3, below.

rcr5-05

Image 3

I haven’t tested how long the new SUPER-Super-CAP will preserve time and settings in the RCR-5 but it kept its memory for the 20-to-30 minutes that it took for me to reassemble the RCR and move back to the bedroom. I don’t intend to test this – I’ll wait for the next prolonged power outage to find out.

 

 

 

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Tempered Glass Smartphone Screens

I just finished installing five tempered glass screen covers onto two LG G2, one Motorola G5 Plus and two Samsung Galaxy S5 smartphones. I used Supershieldz because of many rave reviews about their product. Well, I’ll add my rave review. They make a great product. four of the five installations produced flawless results – and they not only protect the screen but resist fingerprints (oleophobic). The fifth installation was on one of the Galaxy S5. It has a new aftermarket Chinese digitizer screen which has no coating and the de-linter stuck too firmly to it, causing the temporary sticky tape hinges to come loose. While struggling to get the screen on, I apparently knocked a single little dot of lint onto the screen near the edge so it isn’t a flawless installation – nearly so but not quite.

The Installation process can be watched on this  YouTube video

 

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Electronic Geocoin

I used pcb-rnd to design a Printed Circuit Board (PCB) with a “geographical” shape, the shape of the state of Florida, for a Christmas present of six assembled devices for my brother who lives in Ocala Florida and is an avid geocacher. His geocache handle is marked on the board (obscured in video for his privacy) as is a space to write a tracking number. The LED at the “OCALA” logo will flash every 30 seconds. These electronic circuits are “trackables” that he will deposit in a geocache with the idea that it will be moved along. However, trackables are often kept by the finder as a souvenir.

The boards were fabricated for me by OSHPark using my gerber files and I hand assembled them.

FYI – pcb-rnd is an Open Source printed circuit design software project. It is under very active development with new features being added every week. It is available for Linux desktop (various distributions, from source), official packages in Debian, Ubuntu,Fedora and Mageia, Arch Linux (user package), Mac OS X , IRIX 5.3 ,OpenBSD and (Likely: any 90’s UNIX system with motif). If interested,check it out at: http://repo.hu/projects/pcb-rnd/

Video showing the electronic geocoin

 

Posted in Electronics, geocaching, Linux, PCB Design | Tagged , , , , | 1 Comment

Smartphone screen adhesive – some empirical information

When installing a replacement screen on a Samsung Galaxy S5 I used a Chinese
product named “ECO-FUSED” in a 2mm width. When I removed the original factory adhesive I noticed that it seemed a bit thick – certainly thicker than
the ECO-FUSED product. I had a lot of trouble getting the ECO-FUSED to hold
the screen to the body. I deduced that the ECO-FUSED product was too thin
for the Galaxy S5’s adhesion surface area design, especially along the sides. After
three tries I ended up using two layers of ECO-FUSED before screen adhesion
looked promising. Even then it still popped up in places. This morning I have applied compression clamps along the edges and I will leave them on for 24 hours
to see if that works better.

OBSERVATION – ECO-FUSED is (1) not sticky enough for good screen adhesion,
at least for this phone; (2) not thick enough for this phone.

I did some research. I measured the adhesive thickness of ECO-FUSED using
a micrometer. Using a piece of paper I applied ECO-FUSED tape to one edge
of a piece of paper, folded the paper to create two paper thicknesses plus
the adhesive in the middle. I then measured the glued side versus the no
glue side to determine the thickness of ECO-FUSED. It is 0.09mm thick. So,
two layers of ECO-FUSED is 0.18mm.

A commonly recommended tape is Tesa 61395. It is 0.2mm thick per the
manufacturer. The thickness seems to be more appropriate for the Galaxy S5
and it classified by the manufacturer as “high bonding strength”. I’m
going to purchase some in case the ECO-FUSED continues to fail for me.
Tesa 61395 tape is readily purchasable on-line.

BTW – Tesa 61345 is identical to 61395 except that it is 0.23mm thick. I
would really like to try a roll of it but it is NOT readily available
on-line.

UPDATE 1: It is now a couple of days later and the result is – FAILURE. One side is holding but the other side has popped loose, as has the top. I ordered some Tesa 61395 tape and hope that it will be delivered this week. I will never use the ECO-FUSED again, at least not for smartphone screens.

UPDATE 2: My order of Tesa 61395 arrived today. I used the micrometer as previously described and, yes, Tesa 61345 is 0.2mm thick. I removed the old ECO-FUSED tape and scraped clean the surfaces clean. I didn’t clean with any solvent because all that I have handy is rubbing alcohol with high water percentage and some Naptha. The Tesa 61395 “seems” to adhere better but the bottom of one side is being stubborn about sticking. Some hair drier heat, some spring clamps and I’ll let it sit overnight. Time will tell.

UPDATE 3: Tesa 61395 IS the best solution. Its adhesion works beautifully. Throw all other tape away!

 

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Fixed Samsung TV Turning On & Off

My 40″ Samsung TV model LNT4053HX/XAA developed a problem where when first turned on it would make clicking noises and turn on and off until it finally stayed on. I lived with it for a few months but it progressively took longer and longer to fully turn on. Before I purchased a replacement I decided to search the Internet for a fix. I figured that others may have encountered the same problem. Sure enough Paul of TampaTec YouTube channel explained exactly how to fix my problem. It seems that Samsung engineers under-specified the TV’s power supply capacitors and they were swelling up and failing. I ordered the five capacitors that Paul indicated were usually the problem.

Today, I went through the significant trouble to remove the TV from its tight, cable-full under-counter nest, took out many screws and opened it up. The power supply had one, and only one, capacitor that had failed, see photo below. After scrutinizing all of the power supply capacitors I decided (fingers crossed) that the other four were OK and only replaced the obviously bad one. IT WORKED – the TV now powers up correctly and, hopefully it work for years to come. Thanks Paul of TampaTec YouTube channel.

Bad TV Capacitor

Bad TV Capacitor

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Inexpensive ESP8266 in UNO Form

Two+ weeks ago I purchased an ESP8266 Module board in an Arduino UNO form factor. See Fig.1, below. It cost me $3.20 US including shipping from China, I didn’t need it or even have a use for it, that I can think of, but at that price, why not. By the way, the seller (Aliexpress seller ShengYang Store) has since dropped the price to $3.16. Delivery took 17 days, which isn’t bad – I’ve had Chinese delivery take much longer. The official product name is “WeMos D1 WiFi uno”.

WeMos D1

Fig. 1: WeMos D1

As soon as I received the WeMos D1 package, I wanted to test it. The D1 has a traditional Arduino UNO Power Barrel Connector Jack but also a micro-USB connector.  Obviously, the Power Barrel Connector Jack only supplies power but the micro-USB connector may be used to supply the 5 Volts and also a bidirectional serial communications interface.

The micro-USB connector serial communications interface utilizes a CH340G I/O chip which requires special drivers with Windows but often “just works” with Debian derivative Linux distros, like Mint, which I used to use. This is because Mint is built with the CH341 Linux kernel driver already installed.  I now run Manjaro on my desktop and I discovered that the CH341 Linux kernel driver is NOT pre-installed in Manjaro. The D1 board was detected and I could even get a /dev entry once I built an appropriate /etc/udev/rules.d rule:

SUBSYSTEM=="tty", GROUP="users", MODE="0660", ACTION=="add", SUBSYSTEMS=="usb", ATTRS{idVendor}=="1a86", ATTRS{idProduct}=="7523", SYMLINK+="wemos"

This created the /dev/wemos entry but not /dev/ttyUSB0, which I needed for communications. I needed the missing CH341 driver (lsusb indicated that it was absent).

$ pacman -Qs ch341
local/i2c-ch341-dkms 20151116-1
    CH341 USB-I2C adapter driver

Once I installed the ch341 kernel driver the /dev/wemos is created as well as /dev/ttyUSB0, which is actually a link to /dev/wemos.

$ ls -l /dev/ttyUSB0
crw-rw---- 1 root users 188, 0 Sep 25 11:57 /dev/ttyUSB0

So far, so good. Now I could finally load some code to test the wemos D1 board. A little (previously done) Google’ng lead me to Steve Kemp’s website wherein he has posted a great article titled “Absolute WeMos D1 Mini (ESP8266) Basics“. It was just what I needed. Since he uses Debian Linux I did need a very little minor tweaking but, on the whole, his article is perfect for my system. Rather than go into detail about his code and instructions it is best that you read his web page linked above.

The code installed in my $3.20 WeMos D1 board without error using the Arduino IDE. I then connected to the WeMos D1’s serial port at 115,200, via the Arduino IDE’s monitor function,  and pressed reset on the WeMos D1. The displayed text displays the URL to access the web server running on the WeMos D1

Connecting to SSID
.
WiFi connected
Server started
Use this URL to connect: http://192.168.1.67/

The web server running on the WeMos D1 presents two links that turn on/off an LED of the WeMos D1 via the Internet. Very nice! BTW – the logic in Steve Kemp’s source is inverted, at least for this board, and “off” is “on” and visa-versa. I haven’t changed it yet.

Led pin is now: Off

Click here turn the LED on pin 2 ON
Click here turn the LED on pin 2 OFF

 

I’m not sure what I’ll do with the WeMos D1 but for $3.20 I am impressed.

P.S.: I suspect that the WeMos D1’s low price is because it is may be a discontinued product and the seller is dumping inventory.

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Pololu USB AVR Programmer V2

I recently purchased another ATmel AVR programmer. I normally use a USBasp programmer with out-of-circuit chips and, less frequently, in-circuit chips. Anyway, Pololu is an electronics manufacturer based in the USA, specifically Los Vegas, Nevada. I’ve previously used a couple of their products and they are of good quality and are well thought out. This isn’t a product endorsement – I simply like the product.

Pololu USB AVR Programmer V2 interested my because of its unique features combined with a bargain price and good support. So, I made a short video of using the Pololu USB AVR Programmer V2 with the Arduino-IDE. I also tested it using avrdude in a Makefile but that isn’t shown in the video. The video shows me using a ISP-6 to ISP-10 adapter because I was programming an ATTiny85 DIP in my old homemade universal programmer socket adapter and it only has an ISP-10 connector.

Interesting features:

  • Connects to computer through USB
  • Emulates an STK500 programmer through virtual port
  • Works with standard AVR programming software, including Atmel Studio, AVRDUDE, and the Arduino IDE
  • Configuration software provided for Windows, Mac OS X, and Linux (not manually configurable)
  • Supports 3.3 V and 5 V devices
    • can be configured to auto-switch operating voltage based on detected target VCC
    • Can optionally power the target at 3.3 V or 5 V via Pololu provided configuration software
  • USB-to-TTL serial adapter for general-purpose serial communication – pinout of commonly-available FTDI USB-to-serial cables allows plugging directly into some Arduino-compatible boards, such as the Adafruit Trinket.
  • Provides a 100 kHz clock output.
  • All I/O pins are protected with 470 Ω resistors
  • 6-pin ISP connector

pololu-pins

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