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Mar 25, 2004, 10:31 PM
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rtideas's Avatar
How about a port for a high intensity LED to flash when a picture is taken.
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Mar 25, 2004, 10:47 PM
Look! Up in the sky!
eBird's Avatar
I like the LED idea. My Optio is so quiet, I know I'll never hear it when it takes a pic.

If not the LED, how about an output for a really loud peizoelectric buzzer of some kind? Those things are tiny and can emit a loud fraction-of-a-second chirp you could hear from quite a ways.

It's really nice to get confirmation a shot was taken.
Mar 25, 2004, 10:47 PM
Senior Member
zagisrule!'s Avatar
Ok, the switch already IS programmable...and already has high-intenstity lamp to show a picture was taken!

All that is coming to you for $20 shipped, adding an audible lost model alarm will be a $10 or so upgrade. The base model already includes a bright red LED that flashes when signal is lost, but we all know that we need to hear it? I will begin accepting pre-orders very soon, coding is nearing completion unless I have to add more features

You have some good ideas in your posts. I only sample the input once per cycle, and I have never had any problems. I wonder why you had problems?

You have some good ideas. I am looking into the mode switcher, but the USB tear-down seems a bit excessive for the average hobbiest to perform. I think just installing a new connector would be easier and safer to attempt so as not to ruin the camera.

Thanks guys!

Mar 25, 2004, 10:54 PM
Senior Member
zagisrule!'s Avatar
Looks like I just missed your post Steve,

Like I said, I have 2 LED's on there now, one for status and one for lost model / camera shutter. The LMA model already has a beep function when you snap a picture, change modes, or reset the programming, but that is only on the upgraded model. I want to keep the base model as small/light/inexpensive as possible for those that like to "keep it simple" I figure $30 for the LMA model is still quite reasonable and there would still be quite some people to buy it, despite it's slightly thicker size and higher price.

Do you guys think my prices are fair? Final size of the base model is about .35" X .45" and would weigh very little.


*edited for bad spelling*
Mar 25, 2004, 11:34 PM
Registered User

Just take this as professional advice - or ignore as you see fit

Non-technical readers should skip this post!

I think that in the interests of 'good design' you should be filtering the input state - and requiring a number of 'good' consecutive input pulses before turning the shutter on and similarly before turning it off.

It is relatively easy to get a stray 'bad' servo pulse. These are filtered in a servo by a number of mechanisms - including that there is a limit to how far a servo can travel in ~20msec.

The issue here is the performance of the device under less than ideal conditions. In ideal conditions the simple vs. the 'filtered' device will work the same - however in marginal conditions there will be a big difference.

Another reason I would suggest this facility is required is that if you are using a software loop to read the input pulse width then the stability of the value you read will not be good (the start and end of the input pulse is asychronous w.r.t your code and you can't measure either the start or end point accurately). This means that if the input signal is close to your switching point there is a good chance that you will get an oscillating signal out of your switch. (ie. some input signal reads will be > the switch point and some will be < the switch point). (Edit: this is typically why you would expect hysterisis on an input control like this.)

I would also suggest that if you have never seen a problem it is probably because the camera's switch debouce circuitry is hiding the problem from you. Ie. if you see a 'bad' pulse and blip the camera switch for 20mS the camera is probably ignoring you.

Last edited by TugBoat; Mar 25, 2004 at 11:37 PM.
Mar 25, 2004, 11:52 PM
Senior Member
zagisrule!'s Avatar
Taken as proffessional advice. Ignoring such advice would only be foolish. I don't see any reason not to filter at this stage of design. I am going to work this out. I have noticed on my scope that input signals for the same stick position are not the same. They can vary easily by + or - .01 or .02 mS in good conditions with transmitter "held steady". I will re-work the code to provide a multiple-stage process of verifying the desired shutter activation, checking 3-5 pulses to make sure they are close (within + or - .05mS of desired switching position). Do you think 3-5 samplings/verifications is enough or do I need to do more than that? I would think that 3-5 would be the compromise of accuracy vs. response time.

I greatly appreciate the time you have taken to help me out with this Tim. The question is, who gets the switch? Both of you? That is only fair

PM me with addresses, Tug Boat and Darnstrider.
Mar 26, 2004, 01:51 AM
Who needs a pilot??
danstrider's Avatar
Whoa there Tim, it took me two reads to begin to understand your post! I do think I understand now. In my case, some "stray bad servo" pulses you refer to came from inductive spikes from three of my servos, I belive. Someone else explained the phenomon to me, but it boiled down to servo commands that moved the servo motor were sending feedback down the servo lines and into the basic stamp I was using. The spikes were of great enough magnitude (trigger low) that the camera triggered every time I moved any stick to control the airplane. Laugh if you want, but it helped take pictures... the new basic stamp program samples for three consecutive "trigger" commands, essentially making it statistically unlikely (I am told) that inductive spikes will cause a trigger. I have not tried this new program, but I can no longer replicate the problem. And, now my camera trigger is optically isolated from the servos anyhow, making the whole issue pretty much a moot point.

Mar 26, 2004, 03:51 AM
Registered User

Thanks for the offer of a switch, but from personal experience you are going to need all the switches you have - consider mine as 'a spare for when you need it'. Also I can actually make any switch I need myself!

Without going on too much - the clue to what is happening is what you say: 'They vary +/- 0.02ms'. Actually if you look at the receiver output with an analyser I think you will find it is remarkably stable - the signal doesn't vary much - the 'error' is in the sampling in the PIC. Your software loop measures in 0.01msec steps. As a result it can 'loose' (or gain) 0.01msec on the beginning and end of the sample - hence +/- 0.2msec. (This is a bit subtle - try drawing some diagrams...)

You are also correct there is a trade off between response time and error rejection - welcome to the real work of engineering

I have been using 5 (about 0.1sec) and never really noticed the delay. Based on my experiments I think you are correct about 3-5 is probably about right.

Mar 26, 2004, 11:10 AM
Senior Member
zagisrule!'s Avatar

Why did I think you would say that? Thanks for your help!

I was not using a PIC, that was the rx signal out, straight to my ocilloscope, a Tek TDS3032. Usually the signal was stable, but on occasion, I would get one that is up to .02 mS off of what it *should have* been. Your explation makes sense though for PIC-based readers.

I am going to use 5 samples of the input to "Verify" that the user really does want the shutter triggered.

Thanks again TugBoat.

Mar 31, 2004, 10:08 PM
Registered User
mike50's Avatar
I would also suggest that once you decide to trigger the shutter, you should hold it triggered for some reasonable amount of time (I think the MR RC-CAM switch holds the shutter triggered for 250 ms or so) regardless of subsequent input pulses. It is hard to know what a camera might think of someone pressing and releasing the shutter button in 20ms.

Apr 01, 2004, 01:50 AM
Registered User
Rogerdoger's Avatar

Good Ideas

Reading this thread has been a trip.

I have to get some coffee!!

Apr 01, 2004, 11:52 PM
Senior Member
zagisrule!'s Avatar
I already pause 500 mS, thanks anyhow for the suggestion.

Yes, you do need that coffee!

Everyone who will eventually want a switch....

Features are now as follows:
-Shutter and mode button control on one channel (Danstrider's idea? A few people touched on it (ZRX Doug, Vince in Texas) but danstrider hit it on the head?)
-User programable shutter and mode trigger points
-Lost Model Alarm and beeps as suggested by Dax
-Zoom controls (the hardware and software is there in my switch....but it is up to you guys to determine the best way to actually get in into the camera) as suggested by Extremeone
-Two super-bright LED's as originally planned for indicators
-Multiple filtering stages as suggested by Tug Boat and Danstrider
-Auto-mode, takes a picture every 3 seconds regardless of radio input, still allows mode change commands
-Wake-up feature keeps camera's from falling "asleep"
-Both open-collector and open-emitter circuits for both trigger and mode controls allow these switches to be used on any camera commonly used for AP
-Sized at .48" X .57" with all these features!

Price will be $20 each for a "Base model" that includes all the above features except the buzzer for the LMA and confirmation beep feature. Price will be $30 for the "Advanced model" with all above features.

I will be taking orders in a week to two weeks, I still need to order the production run of PCB's for these and then I can start shipping soon after that.

Thanks everyone for their interest and input!

Last edited by zagisrule!; Apr 01, 2004 at 11:55 PM.
Apr 02, 2004, 03:25 AM
There is no spoon
Dax's Avatar
Your the man. I might need to purchase more of these things after my flying buddies check mine out. I am in the process of building a web page to show off arial photos to realitors.

Once again, cudos to you man.
Apr 05, 2004, 09:10 PM
Who needs a pilot??
danstrider's Avatar
Hey Matt, how goeth the switch building? Was just cruising the forums and thought I'd ask... haven't had any more idea inspirations but it's been a busy week :-)

Apr 05, 2004, 11:21 PM
Senior Member
zagisrule!'s Avatar
I have ordered the final PCB's and parts, and am gearing up for a long night of soldering the things together later this week. It will be a week or so before I have my website up and taking orders.

I will be accepting payment by PayPal, Check, or MO.

Anyone interested in buying a unit can contact me via: