TPB #20 – Hacking a Yongnuo RF-603 Wireless Flash Transceiver

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The goal of this weeks video was to modify a Yongnuo RF-603 wireless flash system to work with the Camera Axe. I describe the process I go through to hack the device. In the end I find it doesn’t work with the Camera Axe because it’s trigger voltage is too low. If anyone has ideas on how to improve it or a different wireless flash system to try let me know.


About the Author:

Maurice is a computer engineer, photographer, and all around renaissance man.


  1. Blaise - French Riviera Wedding Photographer  September 15, 2011


    I have created my own version of a camera / flash trigger. It’s been a blast learning the arduino and coding. Just saw your video of the 5.1 software – I’m extremely impressed 🙂

    Anyways, I was able to successfully trigger a wireless flash thru the Yongnuo RF602 RX/TX combination. The TX is connected thru a standard 3.5mm to PC cord – indeed the RF602TX still has a PC port (later versions – the RF600 which is newer – do not!). No problem at all triggering thru a 4N35 optocoupler. I can’t help you unfortunately with your problem having neither your 4CH opto nor the RF603… Good luck!

  2. Maurice  September 15, 2011

    Have you measured the trigger voltage on the transmitter for the RF602? If that works without modification that would be pretty cool.

  3. Walt  September 15, 2011

    I have been using the Cactus V5 wireless system out of the box with great results. I hook up the Cactus to the CA usingt the camera/flash port. I set that Cactus unit as the transmitter. I then use my other 3 Cactus units as receivers. Works like a charm. No mods necessary.

  4. Alexander Kondratovich  October 27, 2011

    Because RF-603 hot-shoe not have a clamp and no LED focus assistant !! I very dissapointed in 603..
    My idea is – adding cord for get sync to from PC-plug on the camera. And leave my 580exII on the camera hot shoe.
    Im trying, but it doesn’t work because it is necessary to receive wake-up signal from Canon hot-shoe.
    I don’t know how to put “logical 1” on a yellow wire of input hot shoe.
    Any ideas?

  5. Caz Mockett  November 12, 2011

    Hi Maurice

    I’ve been using the Yongnuo RF-602TX trigger directly driven from the Camera Axe – seems to work fine for me. This means the TX can be right next to the board and the flashes can be quite a distance away picking up the signal via the RF-602RX unit attached to each. Worked straight out of the box (once I had sourced a 3.5mm jack to PC sync lead). I must admit I hadn’t seen this post before I plugged it all in – so I never thought about trigger voltages – ooops! Guess I just got lucky as nothing blew up 😉

    Anyway, the RF-602 TX/RX combo is older than the RF-603, so you can pick them up quite cheaply – just did a search on eBay (UK) and plenty of choice. I think I might order another RX unit so I can expand my flash possibilities further.

  6. Maurice  November 12, 2011

    Thanks for all your suggestions. I actually have an rf-602rx unit and might get some of the others people have said that work. It’s certainly on my list for future experiments and I’ll do a video when I do the experiments. It will probably be awhile before I get back to this since I have a long list of videos and some of them are higher priority.

    I really appreciate the feedback!

  7. Capn Scott  January 24, 2012

    I took the 3.3v from the arduino and touched it to the top right pin (next to the big pin) with ground to base plate and it lit up the other LED on the 603c (I read somewhere that the camera provides around 4v on half press shutter). After it was lit, shorting the ground and the big pin fires it…

    Thanks for your blog…

  8. Maurice  January 24, 2012

    I would not recommend doing what Capn Scott did. This isn’t a safe thing for some flashes because they depend on low currents.

  9. Capn Scott  January 26, 2012

    This was not done on a flash. It was done on the 603c trigger…

  10. Renan  January 26, 2012

    The problem is your opto isolators are transistor based, you need use MOSFET output, the problem is the .7 drop voltage on the transistor is too much for the 3V of the RF-603, the .7V maybe considered a unknown state instead of a 0 state.

    • Capn Scott  January 28, 2012

      I measured the pin on the camera against ground and it is exactly 2.35 volts. Using an lm317t and 390 and 330 ohm resistors I’m providing 2.33 volts and it is working perfectly… Woohoo, now my drip trigger is triggering wirelessly through the Yongnuo 603c’s…

      • Shlantz  July 1, 2012

        I didn’t understand which pins exaclty you connected to 2.3V, can you explain again?
        are you using RF603 for nikon or canon? did you connected the 2.3 on the upper hotshoe (where there is a big pin) ?

        I want to make my RF603 get a sinc from a camera without connecting it to the hot shoe


      • Robert Duffy  July 11, 2012

        I realise its been almost 6 months since you posted this, but I tried it and it works perfectly, I am laughin my ass off I’m so happy. bought 3 youngnuo rf603c (for canon) units thinking they would work in my pentax kx. no joy, was raging, spent 2 days tryin everything I could think off, shorting the contacts etc to try and get them working. googled it and found this thread. I used the Lm317t with a 390 and 330 ohm resister and it worked better than I could have imagined. Brilliant Capn Scott well done on this fix. google Lm317t voltage regulater circuit, build it, its tiny and simple no circuit board needed, voltage in from plus side of battery (duh!) voltage out to J6 (yellow lead on hot shoe) and ground to ground. ps you only need to modify one unit and use it with the camera all the time

  11. Patrick  March 1, 2012

    Pour le RF-603c pour un PENTAX K5, la solution est peut ĂȘtre de connecter directement le bouton de contact manuel (dessus le rf-603) au contact du sabot ( G vert / centre du sabot J5 blanc ) . Je n’arrive pas Ă  dĂ©monter le circuit electronique de la partie supĂ©rieure en plastique, peut ĂȘter est-il collĂ© ??? .
    Tous les appareils photo déclenchent le flash par ce contact central du sabot.
    Si le J6 jaune attend un signal … il faut le dĂ©ssouder.
    A essayer …

  12. david werdiger  April 5, 2012

    Some truly exceptional articles on this internet internet site , thankyou for contribution. 311989

  13. Donavan  March 19, 2014

    Has anybody been able to successfully reverse this hack? I have now received my version 2 set and wanted to use my hacked one as a receiver again. I removed the resistor, but it will no longer trigger as a receiver. If I add the resistor again it still works in hacked TX mode.