Missing base current limiting resistor for Q4

[rastikw]

When Q3 is open this component is the only thing to limit base current of Q4. With enough IR light this can be in tens of mA. I suggest adding a resistor.

[twam]

Thanks for the hint! I'll take care of it, when doing a new revision!

[GhostDog98]

This has not been added from my eye, should I upload a photo of the appropriate bodge that needs to be done?

It looks like a 220 ohm resistor from pin 2 of SFH309FA-4 to the collector of Q4 seems adequate as that would limit it to 9.2ma under surge output from Q3, and 1.75ma for a more reasonable 3ma output from the photo transistor?

[twam]

Yes, please.