Tag: Hardware

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Utilize Unused Footprints on 5V LCD Modules

Some LCD modules have unpopulated footprints on the back (see Photos 1 and 2). Usually these pads are for ICL7660 (MAX660, MAX1044, or compatibles), a switched-capacitor voltage converter. This post is to attempt installation of MAX660 on dirt cheap 5V LCD modules and 3.3Vizing them.

Note: The article is nothing to do with GoPro. This is related to our another project “NFC tags for schools”. A summary of the product will be shown at the end of post.

1602A-b
⇧ Photo 1: HJ1602A, Shen Zhen Huijing Technology Co., Ltd (cn: 深圳绘晶科技有限公司) [395JPY at Aitendo, Tokyo, Japan]

0820-b
⇧ Photo 2: Seed Studio LCD104B6B or TOPWAY LMB0820D [570JPY at Sengoku Densyo (ja:千石電商), Tokyo, Japan]

1. Why 3.3V?

These days many devices are working on 3.3V or even on 1.8V, for example, GoPro is on 3.3V, and Intel Edison is on 1.8V. However, liquid crystal displays (LCDs) are usually on 5V, because they are made out of 1980s’ technology due to Hitachi’s de facto standard LCD controller chip HD44780.

Thus there are many sites explaining 3.3Vizing of LCDs, for example,

The latter author did a very similar thing to the current article (i.e., he mounted ICL7660 to another LCD). So I’m afraid this post might be a kind of “reinventing the wheel”, but writing this now because it might be useful to someone especially who can actually go and buy these LCDs in Tokyo.

2. Experiment

It seems that HJ1602A (Photo 1) is sometimes sold with ICL7660 mounted. Fortunately we can find such a photo at Magyar site (see “6_2. ábra”). So the LCD is very easy to 3.3Vize as in the following picture:
1602A-a
⇧ Photo 1′: Mounting MAX660 to 3.3Vize HJ1602A

Note: U3=MAX660, C1=C2=10uF, J1=J2=open, J3=close, R8=330 (R8 for back light current restriction at 3.3V)

For LMB0820D (Photo 2) we haven’t yet found any picture on the Net with ICL7660 mounted. But we have already learned how to mod it from two examples above:
0820-a
⇧ Photo 2′: Mounting MAX660 to 3.3Vize LMB0820D

Note: U2=MAX660, C2=C3=10uF, R6=R7=10k, R8=75k, R10=560 (R10 for back light current restriction at 3.3V), JP5=JP8=close (for enabling back light)

3. Results

Here are the results of mods:
1602A-u
⇧ Photo 1″: HJ1602A at 3.3V

0820-u
⇧ Photo 2″: LMB0820D at 3.3V

These are worked on Intel Edison Arduino Board set 3.3V and/or Intel Edison Breakout Board with FXLA108, a dual-supply 8-bit signal translator.

PR: NFC tags for schools

At the beginning of the current project we like to vet some usable LCDs for our purpose: an electrical roll book for schools. The roll book device is required to be able to:

  • Communicate with Google Spreadsheet through 5GHz Wi-Fi network (for uploading attendance/absence records and downloading the list of registered students)
  • Read NFC tags embedded in student ID cards
  • Show results instantly while scanning an ID

Aiming these we have decided to use Intel Edisons for the CPU and Sony RC-S380 for the card reader. And then we came to choose one more item, some brand of low cost LCD works on 3.3V.

edison
⇧ Prototype of our Electrical Roll Book Device: Intel Edison (left), 3.3V LCD (right), Sony NFC reader (bottom)

This device is nearly completed by now, and one unit of system is fixed to be delivered to a collage in Shizuoka, Japan.

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You Like Underwater Selfie?

Adding a programmable switch to MewPro helps us, for example, to take selfies underwater.

No one is eager to drill a hole in underwater housing. But sometimes you might dream if there were an extra switch for customizable functions in GoPro then some great photo/video of something great (or GPOY) could be shot.

In this post, a method to use a reed switch and a magnet with MewPro is addressed. No drilling into housing will be required.

Parts List

  1. MewPro system (GoPro Hero 3+ Black, MewPro, Arduino Pro Mini)
  2. reed switch
  3. magnet
  4. (bits of solder and wires)

reed-switch-and-magnet
⇧ center: reed switch (cost about 2USD), right: neodym magnet (cost less than a dime)

The reed switch will be closed when magnet field is applied. The neodym magnet has strong enough force even from the outside of housing.

Wiring is simple as the following figure:
reed-schematic
⇧ connect D5 and GND pins to either leads of the reed switch

WARNING: Reed switches are very fragile; contacts are sealed in a thin glass envelop. Don’t bend the leads of switch or you will easily destroy/crack the glass.

reed-soldered
⇧ electrical wires are twisted around the straight leads before they are soldered

reed-sw-back
⇧ reed switch w/ a prototype of MewPro in GoPro housing

MewPro Software Mods

In MewPro.ino find the lines

//********************************************************
// f_Switches: One or two mechanical switches
#undef  USE_SWITCHES

and modify them to

//********************************************************
// f_Switches: One or two mechanical switches
#define USE_SWITCHES

This will enable the part of code in f_Switch.ino:

void switchClosedCommand(int state)
{
  switch (state) {
    case (1 << 0): // SWITCH0_PIN
      if (!ledState) {
        startRecording();
      } else {
        stopRecording();
      }
      break;
    case (1 << 1): // SWITCH1_PIN
      startRecording();
      break;
    default:
      break;
  }
}

The statements in case (1 << 0) are executed when SWITCH0_PIN (= D5 as defined in MewPro.h) becomes the GND level, that is, when the neodym magnet gets near enough to the reed switch. The code above does simple things: start recording in video mode (or release the shutter in still camera mode) at the first time it is called, and at the second time stop recording (or no operation in still mode).

If you change the part of code anything can be accomplished. For example, modifying or adding a line of delay(10000); before startRecording();

void switchClosedCommand(int state)
{
  switch (state) {
    case (1 << 0): // SWITCH0_PIN
      if (!ledState) {
        delay(10000);
        startRecording();
      } else {
        stopRecording();
      }
      break;
    case (1 << 1): // SWITCH1_PIN
      startRecording();
      break;
    default:
      break;
  }
}

enables self timer of 10000 milliseconds (= 10 seconds) in still camera mode. Note this self timer mode is usable also in underwater where Wi-Fi is not available.

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Herobus Connector

This post is to compare two similar connectors: GoPro and iPod/iPhone.

Quite a few people have once tried to plug their iPhone plug into the GoPro receptacle (aka Herobus connector). Don’t do that again because it doesn’t fit and it may damage the connector.

Two connectors are the same in pin configurations (i.e., the number of pins, the pitch between adjacent pins, depth and so on) but different in “keys”. To see how keys are placed, look at the following photo and investigate the areas marked by red lines:
female
⇧ GoPro and iPod receptacles (female connectors)

Each of four corners has a different key. Thus if you cut or bend some plastics or metal plates of your iPhone plug, it will become loose and will not mate GoPro.
male
⇧ GoPro and iPod jacks (male connectors)

Part Numbers
For GoPro Herobus: JAE DD1B030HA1R500, DD1B030VA1, DD1P030MA1 (male), and JAE DD1R030HA1R1300 (female). Ridax sells a compatible type of JAE DD1P030MA1 (male).

Note: iPod/iPhone Dock Connectors are produced by JAE, too, but the part numbers are unknown because they are Apple’s proprietary.

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Syncing GoPros

A few people asked us whether or not MewPro could sync two or more GoPros. The answer is YES if you don’t need genlock.

Here is the wiring for syncing:
manyGoPro

This is basically the same to the connection already posted in “GoPro from CANON Timer Remote Controller“. In that article we used rather expensive Canon TC-80N3. But in case that syncing is everything then we can use another cheap remote controller such as: Canon RS-60E3, Rowa Japan RS001 or compatible wired shutter releases for Canon DSLR cameras. (For this blog is dedicated to GoPro, we aren’t going to explain further about general wired shutter releases for other manufacturer’s DSLR cameras although they are also usable.)

A wired shutter release is nothing but a switch of chattering free. When the switch is closed every GoPro’s D2 line get to the GND level and this makes start recording each video (or shutter) simultaneously.

In the figure above diodes are added between D2 and switch. These are necessary to protect the GoPros as each of them is powered by a different battery.
Note: In order to achieve the logic level GND the diodes should be shottkey barrier or low drop (less than 500mV) diodes of same type (eg. 1S4). Don’t use general diodes as they usually have drop off of 1V.