Beam Breaker questions - DPChallenge Forums

Pentax DA 18-55mm f/3.5-5.6 AF

06/22/2006 11:51:44 PM · #1

OK, I'm working on building myself a beam breaker as described in hughletheren's fantastic tutorial...

I've got myself a laser level pointer thingy and removed the lens that makes it a line.

Now, I need a receiver that will work with the light from the laser...

The question is... What kind of receiver can I use???

The laser type of beam breakers here in Taiwan all seem to have gone the way of the Dodo. I can only find the type that uses IR beams, which are not directional...

I wonder, can I use an IR photo receiver as my 'eye' for the bream breaker?

I don't want to spend too much money on something that doesn't work... A beam-breaker device that uses IR will cost me around 40 bucks...

I am wondering if there is a lens or something that can be removed or something like this... Is the red light from the laser enough to push the IR photoreceptor over into detection?

I'm kinda stalled so far...

I will next be looking for alternate cheap wired controllers for the 20D. I don't know of any around here outside of the basic Canon version which is around 35 bucks US...

I've got a fairly expensive ADIDT one too, but I'm a little nervous of opening it up and mucking about with it...

I was thinking that I could make the controller for the 300D with the stereo type jack, and make a converter plug in the 30D controller that would use that as an alternate input to the button on the device...

I'm not exactly experienced with this sort of thing, although I'm not completely clueless... maybe.. :)

Message edited by author 2006-07-19 13:32:08.

faidoi

Pentax K10D

06/22/2006 11:57:49 PM · #2

I can't help with your question, but this site might be of interest.

06/23/2006 12:15:57 AM · #3

thanks.

That site uses IR photogate triggers... They seem to only work well when used very close together and cannot be directionalized like a laser beam..

I have no idea if the IR photoreceptor can use a laser light as it's signal... I think it's too far into the visible light spectrum...

I have no idea though...

Message edited by author 2006-06-23 00:17:00.

Prof_Fate

06/23/2006 12:43:17 AM · #4

doesn't the adidt release have a PC connector? that's 2 wire and should be able to connect them and fire the unit?

PW's can be plugged into teh camera to trigger it - perhaps they have an inexpensive something to 30D wire?

Tamron SP AF 28-75mm f/2.8 XR Di for Canon

06/23/2006 12:26:55 PM · #5

Yeah, the ADIDT that I have has a PC connector... problem is, it's 3 times more money than the Canon wired controller... It would be cheaper to pull a Canon branded one and play with pulling it's guts out before mucking about with the expensive ADIDT one...

I'll have to check what is available around here...

I'm still trying to find out if an IR photoreceptor is sensitive to laser light... Or if not, what kind of photoreceptor is?

I would have though that it would be sensitive to it... I've got no way to find out...

Hey, does anyone have an IR camera that you could check this? just find a dead flat surface, and do an IR exposure with a red laser light painting a dot...

If you can, it's be great! :)

cheekymunky

Canon EOS-40D

06/23/2006 01:11:21 PM · #6

A 'normal' LDR would do the job, but then you have to try and shield the ambient light and use it as part of a potential divider, but this will probably result in lots of false triggers. And it might work on the bench, but will go mad under different lighting conditions. Not sure about lasers, but the nice thing about IR is that if you modulate the signal, and only look for that at the reciever you wont get any false triggers as a result of various lighting conditions. A 'schmidt trigger' is a great way of doing this (Thats how TV remotes work). I havent got the circuit at home, but if i remember I'll have a look next week at work. You might be able to adapt it to work with a laser.

If I were you I'd look for 'obstacle avoidance' cicuits and 'micromouse'. I helped students build these little robots at university (using a microcontroller - you dont want to go there!), I'm sure you'll find something if you hunt about!

Good luck, let us know if you find anything useful

Edit:
Have a look HERE for a simple LDR circuit
And there are some useful cicuits HERE

Message edited by author 2006-06-23 14:01:59.

Tamron SP AF 28-75mm f/2.8 XR Di for Canon

06/24/2006 11:48:05 AM · #7

Thanks cheeky!

I should probably reiterate that I'm in Taiwan and I am doing pretty much everything in Chinese which is not my native language... I do get by, and I did manage to guess the correct wording for 'photoreceptor diode' which I was pretty proud of...

Next, I have to go see if I can find this Light Dependent Resistor thing... Different from a photoreceptor... at least in the translation to Chinese...

I was thinking about using a black drinking straw as a shield. I have a couple of different thicknesses (bought some straws for my photography supplies kit... It's amazing how handy a good sturdy black drinking straw can be! A red filter of some sort should cut out a fair bit of other light as well...

I believe that the reason that Hugh went with a laser trigger was because of the extremely confined beam that it has...

Message edited by author 2006-06-24 11:51:28.

cheekymunky

Canon EOS-40D

06/24/2006 01:08:29 PM · #8

No worries! my english is terrible anyway (an i'm english!), your spelling is better than mine!

A black straw would do the job, When i did something similar with the students we used black "heat-shrink", to block ambient light to the LDR, just heat it up with the soldering iron - it works really well!

Good luck, Let me know how you get on!

ralph

Nikon Z9

06/24/2006 01:54:30 PM · #9

what i used was a photodiode/trasistor from an 5.25 floppy drive
should still beable to find one of those
see my version @ timer

06/25/2006 08:10:51 AM · #10

Rofl. Cheeky... my spelling SHOULD be better than yours... I'm Canadian... ;)

Actually not true, I'm Canadian with British ancestry and had heavy influence from my British grandparents who fancied themselves hobby wordsmiths...

Chinese is a recent thing for me...

Prof_Fate

06/25/2006 09:04:02 AM · #11

Back to the remote..the canon RS-80 runs $50 at b&h, the jjc/adidt/uxcell version on ebay is no more than $25. the RS-60 generic (the one for a rebel) is less yet - it has the cord end that goes in the others? if it's just a miniplug you need that is pretty standart, and connet the two wires/contatct and bang, it works.

what are you trying to do actually? a lot of stop motion is done on Bulb in complete darkness, and it's the flash that's triggered to freeze the action. Same timing issues, but perhaps an easier connector?

06/25/2006 09:10:34 AM · #12

Yeah, actually, I'm also considering using a flash mount...

I'm not in Americ, so B&H is not my first choice...

By the ADIDT version, I presume you mean the wired one... I've not seen that in stores here, only the wireless... I would check one out though...

I cannot use Ebay because as a Canadian residing in Taiwan, Ebay's fraud protection will not allow any purchases to go through... I spent 40 minutes on the phone with their help line in Idaho after several failed attempts... It just gets vendors mad at me. They cannot even manually override... pathetic. I have no plan to go back to Canada any time soon and I cannot apply for a Taiwanese credit card for another 4 years at least, so not really an option...

I should think that adapting the device to the triggers should be the easy part... Building it and getting it working is priority right now...

06/27/2006 12:37:50 PM · #13

Just a little further on the Photo Diode thing...

I did manage to find a Light Dependent Resistor at the store (and within 5 minutes too! Sweet!) and brought two home with me... They are called Guang (light) Ming (sensitive) Dian Zu (electric blockers)... Silly me for asking for Shou (receive) Guang (light) KaiGuan (switch) last time... The webpage on LDR's really helped me to figure this out... Chinese is very descriptive.

A small one and a big one... (will post pics later, this is becoming a lower priority for me this week and probably next week as well)

They both seem to be fairly equal in their responsiveness, I only did a preliminary resistance test...

I was told that they were likely 330 Ohm native receptors...

I'm not sure what the power handling is, but they are likely just fine with 3 volts or whatever is in the example by Hugh...

I also picked up some LED's and switches... Time to start looking for a box I think... :)

The way that they seem to operate is a bit different than I expected...

The description of the circuit is that when light is on the surface of the resistor, it decreases the resistance dramatically, thus the circuit is open when light is being fed.... Removing the source of light will close the circuit...

What I observed was a little different...

When the sensor is fed by light (I tried white LED and two different laser pointers), resistance is still full... However, when the light is interrupted, presumably even for a moment, then RETURNS, the resistance drops for just the briefest moment.... I believe that this will still allow the sensors to be appropriate for this function, but it might warrant a bit of a different wiring setup...

Now, having said that, the box that I found this in was labeled in Chinese, but it also had a listing for CSD and CDS (presumably a typo) using English letters... I haven't had time to see what those might be...

The next thing I need to do is to find out what the common trigger points for flash hotshoes are... and find out how they operate so as to trigger a firing... I will start with a flash that I have with very little control.

06/28/2006 01:16:54 PM · #14

Update... Google helped me to find out that a CDS is known as a Cadmium Sulfide resistor... Apparently it's the same thing as an LDR...

I'm still trying to figure out why the function doesn't seem to match what they describe...

Probably my own lack of electrical knowledge...

If it says that while the resistor is receiving light, the resistance drops, why is it that the resistance is near full even when painted with light? Weird... Maybe my light isn't strong enough?

Maybe I should just try to make it anyhow...

ralph

Nikon Z9

06/28/2006 01:26:03 PM · #15

picking off the web
"negative light coefficient - meaning that their resistance falls as the amount of light falling on them increases."

you must have gotten a positive light coefficient one ...
& edit to add ;) :

a phototransitor/photodiode will give a better responce than a LDR
& a CDS device will be somewhere between the two ..
and one more edit :

between the two as in between phototransitor/photodiode and a true LDR

Message edited by author 2006-06-28 13:28:50.

Prof_Fate

06/28/2006 01:28:22 PM · #16

hot shoe flash is triggered by connecting the center pin and the lip of the shoe. i believe the center is + and the lip - (ground) but that may not matter. Older bigger flashs, one with the old HH plug (household) are directional for some reason that i don't get, but hot shoes are simple affairs. all the other pins are for TTL communcation.

07/19/2006 10:29:44 AM · #17

Thanks Prof.

I had a few failures at trying to figure this one out. It seems that the real trick is that you need to actually push the hotshoe connector in. There seems to be a safety kill on it.

Using flimsy little wires got me nowhere. In future, I will either use a cheap hotshoe mount OR test using a peice of metal that has a bit of meat to it clamped down with the hotshoe connector.

Additional information to 'dummies' like me who might be attempting this.

A CDS or LDR resistor does not give very accurate readings when you simply test the resistance. There isn't enough current from the tester to get good results.

I connected two AA batteries plus a small LED in a simple circuit with the CDS and with the laser pointer that I have, I was able to get light.

Now the real trick is going to be getting my head around how to use this to trigger the flash.

I will consider using a bit of clear red plastic or something to cut down other light sources as well as a short length of black straw to really isolate the light source.

Incidentally, either size of CDS appears to work just fine with sufficient battery power with either the small laser (typical keychain laser pointer) or the large laser (laser level). The laser level seems to be a little less focused. Both should work with the sensitivity level of the CDS though... I was testing without anything to shield it too...

Using a shield, I found that using a large shield (like a fat straw, maybe the thickness of a standard pencil was easier to manage than using a narrow shield. It's just a pain in the butt to get the beam lined up properly so that it shoots straight through the tube. I feel that using an inch of black straw (I used a fat white straw, but cut it down the side, lining the inside of it with black electrical tape) ought to be more that sufficient to deal with even strong light interference. I used the black tape itself to seal the holes and attach the sensor, so it's not as important as one might initially think to get the shield diameter closely matched to the size of the photo receptor.

Message edited by author 2006-07-19 11:02:07.

07/20/2006 02:13:36 PM · #18

so I came a long ways forwards this evening in my progress towards getting this toy working... Still 99% based on hughletheren's How To...

I got all the circuitry in place with temporary wiring and alligator clips... Whee... It took me two hours to get the exact peices that I wanted.

I have a couple peices of information that might be of interest...

#1 The ADIDT Wired/wireless remote control for the 20D/30D HAS a standard 2.5mm stereo headphone jack on it. (for those not familiar with this one, it's a really sweet little toy. It has bulb mode, wireless mode [with an FM based receiver with pretty durned good distance ability] and normal mode. It also features the rather important 2.5mm jack.)

The RS-80N3 Canon wired remote has no such jack. Neither does the RS-60 for the Rebel series... Interestingly, the Rebel's wired controller can control the 20D/30D through the jack (it uses that standard 2.5mm stereo plug) as well AND can do so with a dead battery in the ADIDT unit (of course totally pointless seeing as all the same functions are present in the ADIDT unit, also without any battery needed).

If one is interested in building something like this, they could either go with the RS-80N3 and take it apart as mentioned in the tutorial. BUT. If you are also interested in the basic capabilities of the ADIDT with wireless, save the money and do that instead. All you will need to get it to work is a 2.5mm plug.

I ended up using different jacks than the tutorial mostly for availability reasons and pricing reasons...

Receiver: 3.5mm female stereo jack
Into ADIDT controller: 3.5mm female socket to 2.5mm male jack
For primary lead: 2 meter long male 3.5mm jack to 3.5mm male jack

All pre-wired, but quite affordable.
This is good because if I want to, I can get a simple stereo headphone jack extender that is quite long for very little outlay of cash. 2.5mm stuff was hard to find. I will make a little 'sock' for it and keep it in the back with my ADIDT.

Additionally, I picked up a simple unwired, DIY 3.5mm stereo jack for testing purposes.

#2 I took some voltage readings from my 30D and discovered the following. This should be quite similar for most Canon cameras with a wired remote system, regardless of the plug type.

A| ___ |B
. . C

When viewed with the large post at the bottom:

A: Full press lead = 3.2V
B: Half press lead = 4.3V
C: Ground

As mentioned before by the Prof, connecting the B to C will cause the camera to go into half-press mode. Connecting A to C wil cause the camera to go into full-press mode and take a picture.

#3 The voltage figures are relevant because resistors can be a bit confusing (for folks like me who are really beginners when it comes to electronics) in the way that they work in the circuit.

I'm still trying to figure out how the resistors cause the circuit to work.

It's a lot more confusing when just mucking about with the electrical tester.

This is why the voltages are important. You actually need power to the circuit to see how it works (unless I'm doing something wrong which is probable). See below for using a cheap external flash for this purpose.

#4 In the tutorial, Hugh mentions that the switches all need to be switched off and on again just to get do another shot.

I don't want to do that because I don't want to mess around with the possibility of moving the device when I flip the switches. Therefore, I added a simple 'reset' switch in the middle of the main ground line, just before it gets to the battery. All it does is breaks the circuit open when pressed fully. If I place this on the top of the device, it will be perfect!

#5 The really great thing about this design (using 2.5mm jacks) is that it's possible that it's also compatible with a good number of external flashes. My external flash has a PC Sync cord jack that is - you guessed it - 2.5mm. How cool is this? Well, this flash unit of mine is quite cheap, but it can be directly controlled by the unit. Higher end flashes that might use more complicated PC sync cables usually still have a slave flash thyristor. That also makes it a fantastic tester for the device with low risk. No need to make any special hotshoe or anything goofy. Naturally, this particular flash is 3V. It uses two AA batteries. Gotta love the standard!

You don't have to direct the flash light towards the subject for the primary flash to trigger the slaves. The system would work and the flashes would be able to work with E-TTL II if this is present on your more expensive flashes.

OK, this is all for my update tonight.

Message edited by author 2006-07-20 14:15:26.

07/21/2006 12:31:00 AM · #19

Got it working with alligator clamps...

I seem to have a short somewhere because it keeps shorting the full-press circuit. I will have to see if it still does that after I wire it all together properly...

I bought two 5-packs of alligator wire clips instead of wire. Next, I will just clip the heads off and have a bunch of short alligator clips and I will be able to color code the rest of it...

It does need to be reset though after use... It doesn't always work the same that way, but it will keep the full-press circuit active once it trips...

I'd love to find some way to force a reset after 1 second.