A minimal Top Slot, battery failure memory saver for PSION Organiser II (all family) devices. The design reduces risk of internal device memory loss especially due to Lithium-Ion 9 Volt surrogate battery discharge characteristics (limited if any warning). By providing sufficient standby power for longer term internal memory retention and specifically not operation. Permitting hours / days for recharge of main power battery or months of power down whilst preserving the internal RAM contents. The design fits a classic PSION Organiser II Top Slot Case (See all notes).
All the files are required for a complete assembly.
- The default repository format is STEP ( ISO 10303 ) due to its high fidelity.
{ STL files are surface geometry as opposed to solid model representations, often containing export processing artifacts }.
- The default repository format for PCB files is GERBER .
FreeCAD may prove suitable for viewing, handling and, if desired modifying STEP files.
KiCad may prove suitable for viewing GERBER files.
Models might be viewed on line using the following links. Noting display of any mesh lines is a feature of the renderer and are not contained in the source STEP model. It is strongly recommended to use the source STEP file where ever possible, as any export process will introduce artifacts.
The design presents a battery backup system interface to the Top Slot hardware of a PSION Organiser II family of devices. The PCB dimensions (38.0 x 43.6 mm) are ideally suited to low cost manufacture. The 2 layer PCB design provides low cost of implementation. Whilst the PCB space claim is intended to be suitable for a classic Top Slot Case (See Considerations) and construction is through hole PCB based for ease of assembly.
A minimum configuration comprises:
| Qty | Pt. No. | Description |
|---|---|---|
| 1 | Your Ord. No. | 2 layer PCB |
| 1 | Your Ord. No. | Case or Original Manufacturer Part |
| 1 | Your Ord. No. | Screw 2mm x 12.7mm CSK H Selftap (if not using Original Manufacturer Part) |
| Qty | Mouser Pt. No. | Description |
|---|---|---|
| 1 | 512-1N4148 | 1N4148 diode |
| 2 | 712-BAT-HLD-001 | Battery clips |
| 1 | 649-1012938291604BLF | 2 x 8 way Right angle header (~8 mm engagement length, gold plated) |
| 2 | 658-CR2032 | CR2032 batteries or similar |
Optional:
| Qty | Mouser Pt. No. | Description |
|---|---|---|
| 1 | 474-PRT-00119 | Barrel Jack Conn. |
| 1 | 863-1N4001RLG | 1N4001 Diode |
| 1 | 710-151033RS03000 | LED Red |
| 1 | NFR25H0004701JR500 | 4k7 Resistor |
Note:
a) Purchase order quantities may stipulate M.O.Qs.
b) If using the original manufacturer case the connector must be also be used, typically the diode and barrel connector may also be re-used following careful removal.
A classic Barrel Jack (5.5 mm outer, 2.0 mm pin) connector for the ~10.4 Volt 175 milli Amp centre positive pin power supply is located to be compatible with the classic Top Slot Case. The Barrel Jack (This is the same connector used on the classic Arduino Uno and Mega boards), connections are brought to 2 header pins on the left of the PCB to permit alternate power sources to be readily accommodated.
A low voltage 'secondary' power source is held on the PCB to allow for longer term retention when the main power supply or internal PP3 battery become depleted. Switching is automatic via diodes and the purposefully lower secondary battery level restricts usage to notification and memory backup only.
Details on testing and backup battery performance are located in the Top Slot Battery Saver Basic - Testing.
The device is transparent to the Organiser's Operating system and requires no software to operate.
Always ensure a main power source is connected before attaching the Battery Saver unit. This allows the Organiser’s internal capacitors to charge from the main power supply source rather than the backup battery system, thereby extending battery life of the Battery Saver and enhancing overall protection.
The underlying principle of this approach is exemplified by the classic 10.4-volt PSION Organiser power supply, and potentially by other similar models. This power supply incorporates a resistor and Zener diode configuration that delivers a regulated 6.4 volts to the device for a brief duration in the absence of both mains power and an internal 9-volt PP3 battery. This arrangement helps preserve the contents of the internal memory for a limited time—significantly longer than the ~30 seconds afforded by the internal capacitor alone (CM/XP Manual Section 2)—such as during battery replacement.
The operation of the low battery voltage mode is detailed in Section 7.4.3: LOW BATTERY TEST. Typically, when the Organiser is powered on—either by pressing the ON/CLEAR button or through activation of the Top Slot AC line—the keyboard buffer is initially empty. The system then evaluates the battery status by checking the state of bit D0 on PORT 5 of the Hitachi 6303 microprocessor.
In scenarios where the main system voltage is low or absent (e.g. due to a missing or depleted 9-volt battery), the Battery Saver circuit—assuming fresh batteries—can supply approximately 6.3 volts to the Top Slot main power line VB (SVB) via a diode. This enables the system to retain the contents of internal RAM. If the device is activated (e.g. by pressing ON/CLEAR), there is usually enough residual power for a brief startup, during which the “BATTERY TOO LOW” message is displayed on the Organiser’s screen (CM/XP Manual, Section 10).
In standby mode, the XP & LA devices typically consumes 30 uA as described in section 3.4 STANDBY REGULATOR. Later LZ64 models were observed to consume of the order of 2 times the stated value whilst in standby mode (due to increased internal RAM). An XP device was measured at 19 uA continous current draw from backup cells, not including clock maintenance. Assuming high performance Lithium / Manganese Dioxide (Li/MnO2) CR2032's and the device power not activated by pressing ON/CLEAR, the device at room temperature. Memory protection of ~1 year is anticipated, following loss of the 9 Volt main battery power. This would for example result in Lithium-Ion batteries with the Battery Saver unit in effect having similar backup capability to traditional Alkaline cells or increased protection periods for Alkaline cell usage as desired.
Test conditions:
MODEL XP ROM 3.6, 1 x 32k ROM (COMMS), 1 x 32K RAMPAK, Battery Saver Rev 0.1, Panasonic CR2025's
Commence and complete fitting of PP3 battery or mains sourced power, followed by insertion of Battery Saver into Top Slot. No Power refers to removal of main power (PP3 or other).
a) 2 cycles - No Power Source - Off 1 Minute - ON/CLEAR - Low Battery Warning sequences - No issues
b) 2 cycles - No Power Source - Off 5 minutes - Battery fitted - No issues
c) 2 cycles - No Power Source - Off 9 hours - Battery fitted - No issues
Test a) is believed to be the most demanding current draw and simulates the most likely scenario for regular use.
Test c) is believe to be the most realistic scenario for regular use.
All the above tests performed on the same battery set.
It is strongly recommended to follow the testing regimen detailed pre and post assembly.
Most components are traditional soldered ‘through-hole’ types. To ensure high-quality solder joints, clean the PCB and battery clip feet with Isopropyl Alcohol immediately before assembly, and use a quality rosin flux.
Begin assembly with the connector, as outlined in the alignment guide. Then proceed with mounting components on the top side of the PCB, starting with the lowest-profile parts and working up to the tallest.
Correct orientation of the two diodes D10 & D11 is critical to proper operation of the Battery Saver. The Cathode end of both diodes are oriented towards the Top Slot multiway connector (see image, also ).
The final component to install should be the lower battery retention clip. It’s important that the clip’s soldered surface mates directly with the PCB, as the clearance between the lower case and clip is minimal. To prevent the clip feet from lifting during soldering, secure them with Kapton tape or a similar method. This helps avoid excess solder raising the clip, which could cause interference with the bottom cover.
Since the clip acts as a spring once the battery is inserted, the solder joint will be under continuous mechanical stress. Therefore, a strong, clean solder joint—achieved through proper cleaning, flux application, and technique — is essential.
PCB is tested for trace continuity and trace short circuits.
- PCB visual inspection including screen printing, traces, coatings, via quality and dimensional verification
- PCB Electrical verifications for trace continuity and short circuits
Assembled PCB is tested for:
- Visual inspection for connector alignment, component seating, solder balls, bridges or whiskers
- Electrical tests on connector for short circuits
- 0 Volt connection continuity
- Diode(s) polarity test
- Diode type and location verification
- Barrel Jack connector polarity verification
- Battery spring retention check
- Standby battery power provision
Post Assembly tests:
- Insertion into Organiser Model CM
- Test a) and b) included in 1 hour use in Top Slot
Note: tests are performed using the Top Slot Spy and using a MODEL CM device.
Internally a 0.1" header is available to accommodate alternate 9 volt power systems (possibly this and a USB lead).
The unit uses the Vbb and 0 Volt connection of the Top Slot, no other connections are used.
The envisaged use case is in place of the classic power supply adaptor. However, the adaptor may remain in place to protect the internal memory of the unit.
Note it is recommended to:
- Not to have the unit powered when inserting or removing devices
- Connect a PP3 (ANSI:1604A IEC:6LR61) battery to the target unit, followed by inserting the Battery Saver
or - Power from via the external power sourced via the Battery Saver unit
- Use only the original adaptor, or power supply having the same supply voltage
- Following 'Low Battery Notification', replace the main power source promptly
- Replace the Battery Saver internal standby batteries following any extended period of main power loss
- Ensure regular backups are maintained
- Always use a case requiring a tool to obtain access to batteries i.e. screw fixing
Where a Battery Saver unit is inserted into a discharged device without 'internal power', such as a PP3 battery, the units internal capacitors will draw relatively high current from the standby batteries. This will relatively rapidly discharge the standby batteries, reducing the battery capacity available to act for long term storage protection. The design is intended not to provide sufficient voltage to allow operation. Pressing the ON/CLEAR button will result in the unit notifying Low Battery status and powering down.
When the main power source is in a good state, no power is drawn from the Battery Saver standby batteries.
Testing indicates good compatibility, no software is required.
An advantage of using the approach is the use of a classic power supply case with no modification (See note on original connector). Removal of case screw necessitated for secondary battery change, is considered a safety feature (reducing potential risk to young children accessing coin cells).
The device supports extended use from alternate external power sources i.e. without main battery, as when external source removed the Coin cells automatically switch in to retain internal memory. This reduces reliance on 9 volt battery use and would provide up to 12 months memory retention, provided the ON/CLEAR not utilised with no main power source connected (see Testing).
Precautions when using any stored energy device must be employed, with particular focus in this instance on batteries.
Where Coin Cells are used the following guidance may be of assistance:
Guidance:
- Keep batteries away from children
- Always install the batteries correctly as per instructions
- Remove batteries and store carefully when device not in use
- Remove discharged batteries from device promptly
- Ensure that the contact points are clean and conductive
- Do not mix different types of battery
- Do not heat batteries
- Do not attempt to recharge batteries not specifically designed for recharging
- Do not dispose of in a fire
- Do not allow batteries to form a 'Short Circuit' connection
- Dispose in accordance with local regulations, use Re-cycling facilities
- If chemical exposure occurs, seek immediate medical attention
- If a battery is swallowed, seek immediate medical attention
- Always follow battery manufacturer guidance to prevent thermal events
Models or files in this repository make no accommodation for manufacturing tolerances, process or material - see Notes below.
The original male 8 way 2 row top slot header style connector (marked MXS 70224) may have included a custom pin support moulding. Data from a parts list kindly indicated in this hardware forum seemed to confirm this theory. Readily available 8 way 2 row header connectors tend to have smaller pin support mouldings. The effect of using pin headers with smaller moulding is to permit the PCB to displace vertically in the slot guide channel, resulting in poor alignment with the mating female connector and potential insertion difficulty. There are a number of mitigations, such as changing the height of the male header connector in the PCB and adding material to support the top of a smaller male header pin support moulding. The precise accommodation will depend on your selected pin header moulding.
Connecting any device which has not undergone thorough testing, will lead to irreversible degradation!
See Organiser 2 Hardware forum, though see note below first.
Such a system does not obviate the need for standard good practice backup procedures.
Assessment for any fitness for purpose is entirely the users responsibility. Use is entirely at the users own risk. Any degradation to hardware, data loss or corruption is the responsibility of the user.
All information is For Indication only. No association, affiliation, recommendation, suitability, fitness for purpose should be assumed or is implied. Registered trademarks are owned by their respective registrants.