Zoom-Focus-Iris control

 
Thank you for doing this.


Bob Hill said:
Sorry about not getting this posted sooner but I have been really busy. I didn't get part #s for the plugs but this is a good start on materials.

Bob

Potentiometer:

https://www.jameco.com/webapp/wcs/s...toreId=10001&catalogId=10001&productId=241656

Momentary switch:

https://www.jameco.com/webapp/wcs/s...&catalogId=10001&productId=315395&pa=315395PS

Enclosures:

https://www.jameco.com/webapp/wcs/s...toreId=10001&catalogId=10001&productId=675411

https://www.jameco.com/webapp/wcs/s...storeId=10001&catalogId=10001&productId=18922
Click to expand...
 
fantastic info - thanks to all the posters. question - in the schematic, it shows a "manual-auto" switch, but i don't see that in your prototype(s). or am i just overlooking it? Also, I must confess like others here that I'm still slightly fuzzy on the difference between the 4-pin plug and 3-pin plug. definitely want to build one of these things!
 
citizenjournalist,

Your right about not seeing a "manual-auto" switch on the schematic. I didn't have one but it is very easy to incorporate. I can post another schematic with that added if anyone needs it.

Bob
 
Bob,

Actually your schematics do seem to depict the manual-auto switch, it's just that I didn't think I saw any manual/auto switches in the pictures of the prototype you built. If I understand how things work, w/o these manual/auto switches on the controller, then the camera would always be in manual operation mode (when the controller is plugged into the camera), whereas with the swtiches one could toggle between manual or auto (similar to some of the varizoom controllers).

Steve
 
citizenjournalist,

You are exactly right. Without the switches so the camera is in manual mode only. I really need to update my the pics of my equipment. The pictures posted on the forum are from the the very first controllers I made and I just slapped them together with what I had on my bench. They were not very elegant at all ;)

Bob
 
Hi guys,

I finally found time to build this project with my father who was visiting for a week. We had a good time doing it. Pic is attached.

Everything works - mostly quite well - but for one thing. The zoom control has the following quirks, and I'd like to know if this is unique to my unit (i.e. something I did wrong) or whether it's just the way things are 'supposed' to work. First, I have to turn the knob/potentiometer for a while before the zoom 'kicks in' and starts to move. Second, unlike the focus and iris adjustments, which seem to move only when I am turning the knob/potentiometer, the zoom seems to start zooming, and keep zooming (even after I stop turning the knob) until I turn the knob in the opposite direction to "turn off" the zooming - is that normal or some weird anomaly of my build? Any advice/ideas are appreciated.

One more thing - the parts list that was given previously (links to Jameco) has an error - the item that is supposed to be the momentary switch is actually a push-button on/off switch (I know, cuz I ordered it and then realized when putting things together and comparing to the circuit diagram that it didn't do what it was supposed to). This required a trip to Radio Shack and a 3 dollar part, so it wasn't a big deal - just thought I'd mention it for others.

Thanks, Steve
 

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Hey CitizenJournalist,

Focus and Iris relate to exact, repeatable points on your potentiometer (like the spedometer on your car, or hands on your watch). You could mark where the iris hits 5.6 on your enclosure, and that point would always give you 5.6.

Zoom is relative, and uses the resistance points on the potentiometer to tell the camera which direction to move the zoom lens, and how fast to do it. The halfway point on your 20k pot (~10k) tells the camera to leave the zoom where it is. Once you've zoomed to the position you want to get to, the zoom knob needs to return-to-center, to keep it there.

Hope this helps.
 
Nice looking unit there!

Yes, there are some differences in how the controls work.

The Focus and Iris are "Absoloute" controls. Basicaly what this means is that the lens is locked to and tracks the position of the controls. The end stops of the controls match the end stops of the lens. And the lens elements will only move while the controls are moving.
This is similar to the steering wheel on a car, it's locked to the direction of the front wheels.
The benefit is that as any control position always referes to the same lens setting, any adjustments are simple to repeat and you can even mark your controllers with known values.

The zoom controller is "Relational", meaning that instead of the controller setting the position of the zoom, it tells it which way to be moving.
It's more like the accelerator in your car. It doesn't matter where you start, the harder you push, the faster the car goes.
With the zoom control in the center, it's not moving, and the further to each end you go, the faster it zooms in that direction - just like zoom rocker on your camera. To prevent accidental zooming, there is a "null" (inactive) safty zome in the middle. The zoom will only move when the control moves outside this zone. This makes it easy to be sure your zoom is fully stopped, especially on controllers that don't have a spring to return the control to center.
This system allows for smoother zooms as you just hold the control in place and the camera will keep zooming at a contant speed until you use the control to slow it down to a stop.


EDIT: basta73 beat me to it in less words.

- Mikko
 
Thanks for the explanations - now I understand why the zoom is working that way. It still feels like I have too much 'free play' before the zoom actually kicks in; it seems I have to turn the knob quite a bit before anything happens. But I can live with that, it'll probably just take some getting used to.

Cheers, Steve
 
has anyone found a potentiometer that works like a rocker for the zoom? or maybe a fader type that returns to the middle?
 
Thank u all for the precious info...
I read this forum yesterday and bought some stuff today :)
The pots i found are 22 KOhm, i hope they are goin to work fine!
Soon some comments and pics!
 
guysmilez said:
has anyone found a potentiometer that works like a rocker for the zoom? or maybe a fader type that returns to the middle?
Click to expand...


Hey guys...My first post here...Great work to all of you who put these things together and share your ideas. I surely will post my creations once I build them. (and learn how to post, LOL)

Just thought I would say...it would be a great item to add....a wheel/knob similar to the type you find to control pitch on a synthesizer. Albeit smaller of course.

Any suggestions? Of course size is an issue however that spring activated center retent seems like it would be worth some sacrifice.
 
there's a couple of ways a self-centring zoom control could be built in without increasing the overall unit size. Both options use a "momentary on-off-momentary on" rocker switch like this one:

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=360-2261-ND

The idea is to wire the switch in series with either (1) a rotary potentiometer or (2) a multi-position slide switch (like on the DVX100b's handle-mounted zoom control switch). The pot or slide switch is used to pre-set the desired zooming speed. The rocker switch then provides zoom in/out using this speed. Downside is you'll need 2 hands if you want to vary zoom speed during a zoom. Any thoughts?
 
My only question seems stupid but when you connect the ground from the focus pot and the iris pot do you just connect the grounds together and then onto the sleeve? and also there are 3 hooks ups on the pot , but mine are not labeled how do you know what it what
 
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