Daniel Reetz, the founder of the DIY Book Scanner community, has recently started making videos of prototyping and shop tips. If you are tinkering with a book scanner (or any other project) in your home shop, these tips will come in handy. https://www.youtube.com/channel/UCn0gq8 ... g_8K1nfInQ

Two camera sequencer

Everything camera related. Includes triggers, batteries, power supplies, flatbeds and sheet-feeding scanners, too.
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ai4px
Posts: 33
Joined: 12 Dec 2012, 12:47
Number of books owned: 0
Country: United States

Two camera sequencer

Post by ai4px » 07 Jan 2013, 14:41

I've just drawn the schematic for a two camera sequencer that uses pretty much off the shelf parts. In keeping with the idea that these book scanners may need to be sourced locally, I kinda went about this the Rube Goldberg way. Sure, this could be done with a pic processor, but this way can we wired together by anyone with limited skills. The timer relays were sourced from an ebay vendor for $7, the normal relays were $6 each. Why do I need such a complicated lighting setup? I found on glossy books (school books and magazines) that the only way I could get rid of glare was to use two lights. But only one at a time.

My design goals were:
1)cause two cameras to take pictures one after the other and switch lights off that cause glare. Note, I simply don't switch the lights ON when needed, I switch them off when not needed so they stay warmed up for color rendering. Also, it gives plenty of light for viewing the book as the platen is loaded to make sure there are no crinkled or folded pages.
2)Make darned sure that both cameras take the same number of pictures. Once this sequencer is triggered, it will not reset until both have fired.
3)As stated earlier, be duplicated easily.

Now, as for how it works:
1)The user triggers "PB" push button and pulls in the "latching relay" and starts the "kickout relay" timer. When the kickout relay timer activates in 8 seconds, it will unlock the latched relay. The latched setup was intended to allow the user to briefly press the button and ensure that both cameras have time to fire.

2)The debounce timer of one second is used because I want to trigger the cameras from a microswitch on the platen. Depending on the thickness of the book, I'll have to make it switch an inch or so from the dead stop position. So by using this one second "debounce" timer, I can trigger this circuit as I raise the platen and once the book is pressed firmly, it'll fire. This will allow me to use with any thickness book.

3)After the one second settling time, the secondary camera starts it's 3 second timer. At the same time, the "pri camera relay" pulls in and puts power on the bottom 110v outlet and removes it from the top outlet. Since my camera is triggered from a phone USB charger plugged into the bottom outlet, this triggers the camera. The light for the opposite camera is plugged into the top outlet and is switched off.

4)After 3 seconds or so, the "secondary camera timer" pulls in, cuts power to the pri camera relay, and applies power to the "sec camera relay". It behaves just as described above... turns off the lamp, fires the camera. Since the "pri camera relay" is now released, the light attached to it is on now.

The sequencer will stay in this mode until the kickout relay AND the PB are released.

Note that each of the relays have two sets of contacts and only one set is used. This allows for status lights to be wired in, or if needed, a DC voltage to be used to fire the cameras instead of the lower 110v outlets.

The times I used are approximate starting points.

Wes
Attachments
sequencing relays.jpg

ai4px
Posts: 33
Joined: 12 Dec 2012, 12:47
Number of books owned: 0
Country: United States

Re: Two camera sequencer

Post by ai4px » 07 Jan 2013, 14:56

Ohh and one more thing.... if you have an older kodak camera like the dx4530 which aborts saving a picture if you accidentally tip off the shutter before it's done saving, you can extend the kick off timer to an even longer period. That way you are protected from firing the camera too soon.

ai4px
Posts: 33
Joined: 12 Dec 2012, 12:47
Number of books owned: 0
Country: United States

Re: Two camera sequencer

Post by ai4px » 07 Jan 2013, 14:59

In this revision, you'll have a second to abort firing the cameras. The idea for this one is that you'd put a microswitch under the platen when it's in the down position and the switch PB would be pressed as you lifted the platen. You'll have 1 second after lifting the platen to seat the book against the glass. If, when you seat the book, a page looks crooked, you can lower the platen before the "debounce timer" expires and the cameras will never fire. You may need to adjust the debounce timer to 2 or 3 seconds... what ever you time feel comfortable with getting the book seated. You may also wish to wire the unused set of contacts on the "kick out relay" to a buzzer or lamp to let you know both cameras have fired. Come to think of it, it would be really cool if there was some sort of locking mechanism that locked the platen and the kickout relay would release that lock. Maybe a magnetic lock like used on doors?
Attachments
sequencing relays.jpg

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