Powerbank Keep Alive Project


Most powerbanks that have a power on/off switch incorporate automatic shutdown when the load current applied is less than some set value.

This means that trying to operate low current devices attached to the powerbanks becomes frustrating as they keep shutting down.


To overcome this I devised the "keep alive circuit" which pulses the output of the powerbank with a load current of between 100 and 150mA.

The time taken to shutdown varies considerably from device to device and also the current limit is also different between devices.


It is best if you can determine the minimum load current that will be tolerated and use this value for the minimum current being pulled by the keep alive circuit.


This is the schematic for the keep alive circuit.

Built around the NE555 Timer IC chip. The unit is in the astable oscillator configurations

R1 sets the pulse ON time and R2 sets the off interval time.

R3 sets the powerbank pulse current drawn

The capacitor C1 can be increased or decreased for longer or shorter time frames.

The blue LED indicates when the timer fires and the red LED shows the status of the USB supply.

The input is usually connected by a USB male plug and the output a USB female socket.


The values shown give around 3 seconds on time and 5 seconds off time although changing these values may be needed to satisfy your particular powerbank needs.


If the powerbank has a long shutdown time (say 25-30 seconds) and your load current is under 50mA then the switching to the lower power CMOS version of the 555 timer chip and removing the power on led will help to reduce the standby current of the circuit to a few micro amps giving a longer run time before the powerbank is depleted.

Bluetooth Wireless Remote Control Using The BBC Microbit Controller


Cameras like the Panasonic Lumix FZ200 does not have Wi-fi or bluetooth that can be used to provide a wireless remote shutter release.

This project using the very cheap BBC microbit fulfils that purpose.

It can also be used on other Panasonic cameras as a wireless remote without using a smartphone and the Panasonic Imaging app.










The 2.5mm socket on Panasonic cameras provides a 2 wire interface to enable the wired remote controller to either sense the focus button or the shutter button depressions.

By "shorting an element of the potential divider to ground the camera can determine which button was depressed and perform the appropriate action.


The microbit project uses P0 and P1 to turn on transistors which effectively replace the focus and shutter push buttons.













Text Document 1.5 MB




The completed project with the bluetooth remote powered by a lithium coin cell and the receiver at the moment powered by 2 AA


To make the receiver smaller I intend to power it also by a 3v lithium coin cell

The "Spectacular" Audio Project


This was my idea to mount a microphone electret condensor capsule adjacent to the hing on the leg of a pair of spectacles.

These condensor mikes are omni-directional and being so close to the sound source would provide sufficient volume for decent audio recordings.

As they move with your head the audio levels remain unchanged as you head moves.

My first proof of concept used electret mics that were originally used in portable cell phones. later versions switched to the in-line mics found on IOS or Android earphone headsets.










The finished project showing the way that the microphone cable is routed from the rear of the earloop.










the mic element from the in-line microphone is attached to the leg of the spectacles using double sided tape and then a section of clear heat sink tubing was then slid over it to provide both mechanical stability and extra protection.

The cable from the mic being routed down the frame and held in place using more clear heat shrink tubing.








The mic element pcb could be removed from the in-line cable and a new lead soldered to the pcb withe the TRRS or TRS plug depending upon whether the mic was going to be used as a camera input or as a smart-phone accessory.

Modifying the DCC6 Dummy Battery Box to Display Battery Status


The standard DCC6 dummy battery box allows external mains powered adaptors or external lithium-ion batteries to be used with the FZ100, FZ150, Fz80/82 cameras.

When used with the original mains power supply then the battery status is largely irrelevant. However, if you have used an external 8.4v Lithium-ion battery pack then it is important to know what cahrge is remaining in the battery.


The modification here performs that purpose.









The first stage is to open the battery box.


Do this by inserting a sharp blade in-between the hard plastic base plate and the softer plastic cover.


Work the blade down into the opposite corner to split the ultrasonically welded seam.












Cut down to the bottom corner on both sides of the battery box.










Remove any "hot-melt" glue from around the PCB










To complete the modification a 1/8w 10K resistor is soldered from the "T" pad to the negative lead connection pad (black wire).


Once that is done re-assemble the box and apply a little drop of "super-glue along the 3 edges. Capillary action will spread the glue along the seams. Wipe off any excess before it dries.











Now when this battery box is used it will display the current charge status of the external lithium-ion battery

USB-C Power Delivery Adaptor for Digital Camera External Power Supply


Using a ZY12PDN PCB available on Ebay UK or Amazon.com  ( https://amzn.to/37GCuPK ) It is possible to build a USB PD unit to externally power your 8.4v digital camera.




This tiny module provides a means of programming the Power Delivery voltage from the USB-C host device.


It can provide 5v/9v/12v/15v and 19v of voltage with a maximum power of 100W (this will also depend upon the capability of the Host PD device)


The push button is used to set the output voltage. Each depress of the button cycles through the voltages.


It can also be programmed to negotiate a fixed voltage output.

As this unit will deliver 9V at up to 5A (with a suitable host) it can be used to provide the basis of an 8.4volt external power supply if a silicon diode is inserted in the positive output terminal of the device.

This diode will nominally drop 0.6v at typical currents up to 3A.

I chose the 1N5400 as it is capable of 3A continuous current. It would be possible to use a 1N4000 series as in most cases the peak current does not exceed 1.5A with many digital cameras.





This is the completed unit with details of how the 1N5400 diode is connected in the positive output lead of the unit.


The box that I used is from Amazon. https://amzn.to/37DMlpy

The box needs to be filed on the input side to accommodate the USB-C plug.


The PCB is held in place using double side adhesive pad. The output lead is wired to either a 5.5mm x 2.1mm or 4.8mm x 1.7mm plug depending upon the type of socket on the dummy battery box.

the 1N5400 diode https://amzn.to/2N3yzEW









With the suggested plastic case file out one side so that a USB-C plug fits through the aperture.










The PCB is held in place by thick foam based double sided tape

To program this unit to a set output voltage of 9v first disconnect the unit from any power source.

Press and hold the push button down and connect the PD Host.

The LED will flash all colours, release the button and then cycle through the voltages until you reach the one that you require.

You can check the output with a voltmeter or observe the colour of the LED.

For 5V it is RED

for 9V it is GREEN

for 12V it is CYAN

The programming is voltage based and has these steps: 5V, 8-10V, 11-13V, 14-16V, 18-20V, maximum voltage, auto trigger.

By adding a 8.4v lithium ion battery in parallel with the output from the unit (after the series diode) it provides addition current support if needed and also a backup power source if the Host power-bank becomes depleted. At this point this lithium ion battery continues to provide power to the camera. The power-bank can be then exchanged.

If the lithium ion battery becomes partially depleted it will be recharged once this unit is reconnected to the USB-C host again. The usual over voltage/overcurrent and over discharge protection all being satisfied by the battery management board within the lithium ion battery.











An illustration of the ZY12PD board with the series silicon diode and the lithium ion backup battery installed in a small plastic case.





In the latest upgrade of this idea I have included a LED Voltmeter module to draw a slight amount of current from the Host Power Bank.

This 30mA of current is enough to prevent the power bank from going into the sleep mode if there is no load detected.

This is a useful feature as with many cameras going into standby mode this in turn would cause the power bank to go into sleep mode.

It would then be necessary to unplug the ZY12 unit in to wake up the power bank and begin the voltage negotiation sequence again.



To prevent the onboard lithium-ion battery powering the LED voltmeter when the Host power bank is disconnected it is necessary to wire to voltmeter to the +/- outputs of the ZY12 board.

The in series diode prevents the voltage from going to the LED voltmeter module.


I chose a module which drew sufficient current to keep the host power bank, that I normally use, alive but would have minimal effect on the total output capacity from the unit. Some power banks may require a higher standing current to keep them alive. I suggest increasing the current in steps of about 30mA by adding a parallel resistance of 330 ohm if your power bank still shuts down with this module alone.

If the addition 330 ohm doesn't work try a 150 ohm which would add 60mA to the standby current.


the unit that I used https://amzn.to/2sXLm4X








With just the display wired across the output the standby current taken from the power bank was 20mA







Adding a 390 ohm resistor in parallel with the LED voltmeter increased the standby current to 44mA which was enough to prevent all of power banks that I currently use.

The sequence of connection of the unit is important as the serial data communication has to take place to set the negotiated voltage from the host PD device.

When the unit is plugged into the Host PD device the green led light will illuminate denoting successful connection.

If there is no load on the power bank through this unit the power bank may go into a shut down mode.

If you press the power on button to "wake up" the unit it may not correctly communicate with the ZY12PD board and the LED will flash a white/cyan colour.

Unplug the device and reconnect it to correctly restore communication. 

Schematic for the working version of the FZ200 AGC Defeat Unit


The final circuit turned out to be more simplistic than I had originally thought.

I assumed that the input would need to be a sine wave to prevent harmonic distortion if a square or triangular wave was used for the input to the camera. In testing I found that the camera would still perform well with a square wave input so I decide to try both an astable multi-vibrator pair of transistors running at 20 KHz and a NE555 timer IC.

In the end I decide to use the more stable 555 IC as the frequency remained solid even during the battery run down.

Here is the schematic for the project.

The timing is done by R2-C2 giving 20KHz. The output from pin 3 is attenuated by R1-R3  to 7-8millivolts at the camera input after being coupled with the mic input and allowing for its impedance.

the right hand mic input goes straight to the camera input whilst the left hand input has the 20KHz signal injected into it.

If you wanted to get finer control of the AGC defeat voltage  input R3 could be substituted with a 27K resistor and a 100K potentiometer in parallel with it. The output would be taken to C3 form the wiper of the pot. This would allow the output to be set for 0V to about 10millivolts.

The unit is powered by a PP3 9v battery.

Here is the built unit. I used a stereo splitter cable from £/$ store to get the wired 3.5mm inline socket. The 2.5mm plug I wired but again it could be obtained from a 2.5mm to 3.5mm audio cable if you didn't want to have to solder one up.

The version 2 of this unit now features a trim pot (22K) in place of R3 ( the wiper connects to C3) so that you can adjust the level of the bias signal sent to the FZ200. Adjust to about 1/3 or the rotation as a starting point. Do a test recording with the unit on and adjust the trim pot until the background noise doesn't increase when you stop talking.

Modifying the Qutaway 5v to 9v Conversion cable for 8.4 Volts


This is the pcb from the Qutaway product. The case is easily removed by inserting a sharp blade at each corner and prising the two halve apart.


on the left is the input from the USB plug and on the right the output cable.


We are going to add a series diode in the red output lead to drop the 9v to 8.4v as shown below.


Note that the adaptor featured here will support video recording or burst mode with electronic shutter and single mode shooting with the mechanical shutter operative otherwise the camera demands too much current and resets when used with the FZ2000/2500, on the FZ1000 it is OK.

Here you can see the addition of the GP150 silicon diode (or a 1n54 series diode) connected in series with the red lead.


De-solder the red lead from the pcb, insert the diode with the anode (plain end marking) to the pcb and then connect the red cable to the cathode (ringed end) of the diode.

Ensure the diode is clear of the pcb when installed.

Re-fix the covers and add suitable marking to the unit to designate it now to be 8.4 volt output.


The completed unit.


Amazon link for module


Amazon UK http://amzn.to/2w34ZW5

Amazon USA http://amzn.to/2u1w52s