I have developed an external xenon flash for mobile phone

Thread Starter

pyrs9

Joined Dec 21, 2015
12
This thread is coming from the old one: https://forum.allaboutcircuits.com/threads/external-xenon-flash-for-mobile-phone.118781/

The aim of this project is to achieve better quality photos that doesn't appear moved in low light environment.

To do this I have synchronized the trigger of a xenon flash with the picture taking. This reduces the exposure and allows that the picture is taken faster.

The complexity of this project is basically:
  1. Synchronize the trigger of the xenon flash and the picture taking.
  2. Elevator circuit from 5V to 300V required for the xenon flash.
Here is the result:




And here is the schematic:





As you can see, it is composed of:
  • A photodiode to detect the led activation.
  • An elevator circuit to achieve the voltage requirement.
  • And a microcontroller to control the charge and the trigger.


Finally, here is the presentation about the project. If you have some question don't hesitate to ask.
External flash for mobile phone by Jaime Lozano Tortosa on Scribd
 

RichardO

Joined May 4, 2013
2,271
Interesting concept. :D

The only worry is that the flash will cause problems with the phone because of EMI. Do you have shielding that is not shown in the picture?
 

Thread Starter

pyrs9

Joined Dec 21, 2015
12
Interesting concept. :D

The only worry is that the flash will cause problems with the phone because of EMI. Do you have shielding that is not shown in the picture?
Good note! I haven't shielded it. How can I measure the EMI?
 

RichardO

Joined May 4, 2013
2,271
Good note! I haven't shielded it. How can I measure the EMI?
Start by putting the circuit in a metal box. Th only openings should be for the strobe's light and the sensor. Most important is to have a solid metal plate between the circuit and the phone

To prevent other problems, you should also use a shielded cable to the sensor. Alternately, keep the leads to the sensor very short. Preferably have the wires of the sensor solder directly into the PCB. Ideally, only the end of the ensor should stick out of the box. If your battery is not in the metal box then the wires to the battery should also be shielded.
 

Thread Starter

pyrs9

Joined Dec 21, 2015
12
The device is already tested it and it is working fine so apparently has no interference with the mobile. Anyway, I am interested in measuring the EMI.
 

RichardO

Joined May 4, 2013
2,271
Measuring EMI is quite difficult. It takes some expensive and specialized test equipment to do anything definitive. The best you can do is to see if it interferes with radio receivers. Radio receivers will pick up the DC-DC conversion frequency but will not do well detecting the high power flash emissions.

Where are you at? AM radios are a good place to start with here in the US.
 

enscons

Joined Aug 12, 2017
1
did any of u get any luck with the asus zenflash? are they using a custom protocol or an accessory id on the usb otg? the triggering is based on the phone led flash..its not over usb otg...im currently working on integrating the zenflash on other phones...the zenflash software can be installed with a forced software install on rooted devices and it works fine...any help would be appreciated..
 

Thread Starter

pyrs9

Joined Dec 21, 2015
12
did any of u get any luck with the asus zenflash? are they using a custom protocol or an accessory id on the usb otg? the triggering is based on the phone led flash..its not over usb otg...im currently working on integrating the zenflash on other phones...the zenflash software can be installed with a forced software install on rooted devices and it works fine...any help would be appreciated..
I begun with Asus Zenflash but I was not successful (https://forum.allaboutcircuits.com/threads/external-xenon-flash-for-mobile-phone.118781/).

I'm very impressed that it is working fine with non Asus devices. Can you share more info?
 
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