Tic-500 Photonic Type EMI Issue


I’m using a number of Tic-500s in a couple XYZ setups for precision imaging use. I’ve just noticed a potential Photonic type EMI issue with the new “b” version boards (haven’t tried with older version “a” boards). I utilize a group of 7 strobes for lighting, sometimes up to 12, but generally 3~7. Just noticed when the strobes are triggered (all simultaneously) that the X and Y Tic-500s get a “Motor holding because of safe start violation” error, the Z doesn’t but it’s further away from the strobes.

At first I thought it might be an EMI cable issue and tried replacing the USB cable thinking it was coupling EMI and corrupting the USB signal, this didn’t help. So then I covered the Tic-500 with a spare metal reflector and this blocked the safe start violation error, then tried just a business card over the Tic-500 and it also blocked the error. So this pointed to an photon induced EMI type error, and not the usual EMI type issue.

Using some black tape I’ve traced the problem to the Red LED that shows when the motors are active. Obviously LEDs are electro-optical devices (emit photons), but also can convert photons to electrons just like a standard photodiode. I surmise what is happening as the LED is off when the motors are active, and the high intensity optical burst from the strobes is causing a “glitch” from the Red LED and disrupting the Tic controller, causing the Safe Start Violation error.

Anyway, the fix is simple I’ll just place some black tape over the Red LED, although I do like having the visual indication when the motors are active and inactive, which I now won’t have :>(



I was able to confirm this behavior with a standard camera speedlight held above the Tic-500 at 1~2 feet and 1/32 power. I wonder if the pin driving the Red LED is Tristate when off, rather than pulling to ground?



Hello, Mike.

That is an interesting error. Yes, the pin is a high impedance tristate input when the LED is off. It is designed like that primarily so it is possible to chain the error pins on several Tics together and have all of them all halt if one throws an error. We have more details about that part of the circuit in the “Error Handling” section of the user’s guide.

There is an option to “Ignore ERR line high” in the advanced settings of the Tic Control Center software to disable error monitoring on that pin. The Tic will still illuminate the LED to indicate errors if that option is enabled.


Hi Nathan,

Interesting error indeed!! I did go and read the Users Guide as suggested and the error does make sense as the LED supplies enough current when illuminated by the flash/strobe to cause the voltage to rise above ~2 volts I suspect.

I’ll select the “Ignore ERR line high” per your suggestion, so I don’t have to cover the LED (I like the Motor Deactivated feature!!).