TP: Cheap secondary wireless flash?

The Vishay TEMD5100 near IR photodiode may be more sensitive Since it only looks at near IR, it will be less sensitive to ambient visible light. It has a wide 130 degree total look angle. Newark Electronics has them in-stock.

Another canidate is the Vishay BPV11F. It is a phototransistor and the 'F' model blocks visible light and so it only sees near IR. It has a 30 degree total look angle. Newark Electronics has them in-stock.

I'm going to nominate you for diy guru of the flaming year!! This is fantastic.

Alright here is the (I think) final version of my circuit, which seems to be working:


Some explanations:

S1 = On/Off switch
V1 = A 9-volt battery (I have a bunch of these lying around so I'm using this). What's important is that the power source you use is sufficient for U1, the voltage regulator (which requires a minimum of ~7V and also has a maximum allowed voltage, look at the datasheet).
U1 = 5-volt Voltage regulator; this is important, as it ensures a constant 5V is used as logic and Vcc levels. The time delays in the circuit are calibrated for the 5V, so a constant 5V is a must (regular batteries decrease in voltage over time).
C1 = Makes the 5V output less susceptible to ripples/flucuations; does not have to be exactly 0.22uf, just in that ball park (I'm not even sure this is even necessary).
Vcc = Logic high voltage, 5V in this case, just to make it clear.
R5, LED1 = LED to tell if the thing is on (optional). I put a 10k resistor, and with the LEDs I have (just some lying around), the LED is very dim, just enough to tell that the thing is on and not suck too much power. You can use a smaller resistor if you prefer more light (i.e. a 1k).
Q1, Q2 = IR Phototransistor, activates when it detects light. There are two because the ones I got have a small detection angle; this is to increase light capturing. You may want more than two, or if you find a better phototransistor (and I didn't), one will suffice.
R6 = Sets a maximum amount of current going through the phototransistor (the ones I used were 50mA max).
C3, R1 = 10 hz High pass filter; this makes only rapid changes in light to activate the circuit (C3 and R1 are approximate).
Q6 = An npn transistor to bring the state of the NOR gate input low, which occurs during the lighting event.
R2 = Current limit resistor (can be anything over 10 ohms, really).
JK flip flop + OR and NOR gates = Logic system. Make sure you power these, and send VCC to VCC and GND to GND (see datasheets for pinouts). To make the JK flip flop a toggle flip flop, certain pins must be grounded or sent to VCC (see datasheet).
Q3 = P-enhancement MOSFET that charges C2 when told by flip flop #2; this is where the delay comes from.
C2 = Capacitor that charges, creating a delay. R*C should be about 160ms for minolta WL flash.
R3 = Resistor that limits current through C2, creating a delay. You may want to use a 250k potentiometer, which will allow you to change the delay. This is useful if you want to use non-minolta flash systems, or something...
Q4 = An npn transistor that discharges C2 (the delay system) when it is in its resting state.
R4 = Limits current going through Q4 (value is approximate).
R9 = Limits current to the base of Q4 (value is approximate).
Q7/R10/C4/R12/R11/Q8 = A charge and discharge circuit to reset flip-flop #1 (similar to the other delay circuit). This causes the system to reset itself after about a second (i.e. if the system detects a stray preflash and there is no main flash event).
Q5 = P-enhancement MOSFET that triggers SCR1.
R8, R7 = Resistors to provide the correct voltage to the thyristor gate (computed from gate triggering voltage and Q5's on state resistance).
SCR1 = Silicon controlled rectifier (or thyristor), which will create an electrical path on the flash unit, firing the flash.

How the logic works:
During the minolta flash sequence, there are maybe ~7 total pulses coming from the camera. The first pulse and last pulse are the important ones, and we want to ignore the middle few. When the first pulse occurs, the circuit detects this (with Q1/Q6) and sets its NOR input to low. The other NOR input is from the JK flip flop #2's JK2-~Q2 output, which is initially low. Thus the NOR gate's output goes high. This causes the OR gate to go high, and toggles JK flip flop #2, causing Q2 to go low. When JK2-Q2 goes low, Q3 is turned on; this causes C2 to charge. During this state, JK2-~Q2 is high and 'locks' the NOR gate; thus any flashes during this period are ignored. When C2 has charged, it will send OR and ORC to high, which toggles both JK flip flops. The NOR gate is unlocked, and any additional flashes will affect the system (and at this point the only remaining flash from the camera is the 'fire main flash' command, the last pulse).

With JK1, its JK1-Q1 output becomes low. When the final main pulse is fired from the camera, both OR2 inputs will go low, sneding its output to low. This will turn on Q5 and let current flow to the thyristor SCR1. With SCR1 connected to the flash unit, the flash will fire.

One must also determine how the flash unit connects to SCR1. On the ISO hot shoe there are three pins, and on my flash, two of these pins need to be shorted to fire the flash. The center pin should be connected to the high of SCR1, and one of the other pins should be connected to ground. You will need to short these pins to figure out which pins are the ones you need to use.


About the capacitors: I just used whatever caps I had, which were 50V rated (you'd only need 5V rated). I used electrolytic caps, which are polarized, so you must be sure to put the +/- pins to the right sides.
About the resistors: I just used whatever I had, which were 1/4W 5% resistors. Since there isn't any power going through the system, you can use 1/8W or less. Only R3, R8, and R7 really need to be "exact".


I bought most of my parts from www.mouser.com. I got a toggle switch, 9V leads, and a PCB from radioshack (I have yet to construct the final circuit). Anyways these are the parts from mouser I got (I already have resistors, capacitors, and LEDs):

U1: Voltage Regulator (qty: 1):
TL780-05KCSE3

R3: trim pot (if you are using a pot, qty:1):
PTC10LV10-00643-PTC10LV10-254A202

Q1, Q2: Phototransistor (qty: 2 or whatever you want):
OP599A

Q6, Q4, Q8: NPN Bipolar junction transistor (qty: 3)
PN2222A

NOR gate (it's a quad, qty:1):
CD74HC02E

OR Gate (it's a quad, qty:1):
M74HC32B1R

JK Flip Flop (it's a dual, qty:1):
SN74HC109N

Q3, Q7, Q5: PMOS enhancement mode: (qty:3)
VP2106N3-G

SCR1: Thyristor (qty:1):
TYN408RG


Edited by chych - 23 April 2007 at 04:46

Hi all, I've been working on my flash circuit lately and am getting good results. I'm still working on improving my circuit; some things like the phototransistor I bought isn't sensitive enough, so I'm trying to boost its sensitivity. I'll post my final design when I'm comfortable with it. Of course there is another circuit out there (posted earlier in this thread) that does a similar thing (aimed at Canon flash), and I think that one is simpler, but I wanted to take the effort into designing electrical circuits, as I'm trying to learn this stuff. Total cost is something like $15 for one (plus the time involved to build the thing!). Of course, I still need to package my circuit into a nice box with a switch and such.

Here is an image of my Sigma EF-500 (on the right) being fired using WL flash simultaneously with my $15 Vivitar auto-thyristor flash:

Rats!!! That is the same result as the 'Rolf' optical slave I got.

georgiaboy wrote: Well friends I have given the Chinese wonder a real good test. I will describe the sequence of events. 1. I recieved the sensor in a small pink box wrapped up in a Easter bunny and egg bag. No instructions whatsoever. I did, however, contain two disc batteries to power it. It has a small push button switch on one side with a standard female sync port. On the other side it has corresponding leds for the selection chosen. They light up and stay lit when selection is made. On the back is a small 1/8 inch female connection I'm not sure if this is for AC power or older pc sync connector. It has a standard light stand or tripod connector on bottom. On top is the OEM flash connector with one center pin and nothing else. The entire afair is made of cheap thin plastic and might weigh 2 ounces. Because of small rubber feet on the bottom it does surfice as a nice table top stand for most any flash. 2. First test I put a Sunpak 433D in manual mode and and used the On-board flash in PTTL with a Minolta 50 1.7. Camera in Program mode. The Sunpak did not flash. I then pushed the selection button on the sensor to position 1 and tried again. The flash synced and worked very well. I tried all five settings on the sensor and found number "1" was the only one to allow the flash to sync. 3. I then changed lenses to the KM 18-70 DT and changed the A100 to ADI. The Sunpak synced again on selection "1" on the sensor. I also synced on selection "2", but, none of the others. 4. I then returned the sensor to selection "1" and then placed the Sigma 500 DG Super on the camera and set it up as wireless. I then placed the Sigma on it's stand and took a picture. The Sigma, of course, went off but the Sunpak did not. I the tried each selection across the 6 available and basically ....nothing!! 5. I then embarked on every combination of camera/flash setting I could imagine. It would only flash the Sunpak when not in wireless. I tried several different flashes on the camera, as long as it was on camera it would fire the Sunpak perfectly, typically in selection "1" or "2" or both. 6. I then tried using sync cords to string out four other Sunpak 433's. Using non-wireless setup on main flash as above the Sunpaks...none, but the one setting on the sensor, would flash. I then removed them one at a time and still only the one on the flash would fire. 7. I then checked the sync port on the sensor at flash time and there was activation with 5.4 volts present (assuming this to be trigger voltage of the 433). Why it would not sync is beyond me. Conclusion: The Chinese wonder is a total cheap POS. From what we have accomplished so far the same solution for non-wireless multi flash set up can be accomplished using the much better quality Wein Digital PND sensors. Same cost by the way. The real problem is the wireless signals. Not having a solution to prevent early flash while still being able to use the main flash (ie: Sigma 500 DG Super, KM56, etc.) off camera-without teather is the whole problem. I know several of you are looking into this. If you can beat the wireless signal then we should be able to combine the electronics of the Chinese sensor and the wireless signal suppressor. I will gladly loan this cheapo piece of junk for such an undertaking to any of you electronics wizards. It does after all work quite well against any preflash except wireless! C&C Welcome!!!! Aaron

Hope it works for you! Saw the description, says it ignores red-eye preflashes, which is similar to the Minolta wireless preamble flashes. I've just ordered parts for my DIY one, I'll see how that goes.

Well, that's way cool. I am happy for you that the setup is where you are at lease temporarilary happy with it. Untethered camera, is a great advance. I shot some more this weekend with my origial set up and all is ok for me. STILL WAITING FOR CHINESE DIGITAL PREFLASH CANCELING SENSOR!!!!!!

Aaron