Crutschow,

Thanks for the help and especially the patience. So lets see if I understand this or am totally oblivious. Basically, I buy a LM317 package and then assemble it. I assume this means assembling various resistors and capacitors on a circuit board?

Is that the basic idea? If so, can I pick a kit up locally like at a radio shack or is this something I will need to order?

Thanks!

 

Yes. It's a simple circuit with only a couple resistors and a couple capacitors besides the LM317 so you can assemble it on a small perforated board from Radio Shack. The LM317 won't be dissipating much power so you don't have to use a heat sink.

Have you soldered before? If not you should practice soldering two wires together until you get the hang of it. Generally you don't want to apply more heat than you have to, especially with semiconductors, and you don't need a lot of solder, just enough to wet the joint smoothly, not globby. You need to tin the tip with solder before using. A small damp sponge works well for cleaning the tip before each solder application. Touch the tip to the joint and apply the solder between the tip and the joint. Applying a small amount of rosin (not acid) flux to the joint before soldering makes it easier and helps insure a good joint.

They sell small heat sink clips that you put on the semiconductor leads to minimize heat transfer but you probably don't need to do that with the LM317 since it's a power device.

 

Crutschow,

Alright, I am slowly figuring this out but I still haven't figured it all out. My understanding is I need a LM317 and two transistors. I think I understand the formula except for one part, the Iadj(R2) part. I don't understand what the ADJ stands for and then how to calculate the two resistors.

I stopped by one of our two local Radio Shacks today and they were out of the LM317's but I will try the other store tomorrow. I'd really love help putting together a shopping list. Here is what I have so far...

LM317
Resistor A (need to know what to get)
Resistor B (need to know what to get)
Capacitor (size?)
Perforated board

The other thing I need to consider is how to attach this whole thing to the camera and battery.

So what else do I need to get? I hope to finish this all up tomorrow. Now I am off to practice some soldering.

Thanks again.
Drew

 

For 9V out:
R1 = 240 ohms
R2 = 1.46k ohms
C1 (input cap) = 0.1uF for circuit stability (20V or greater rating)
C2 (output cap) = 470uF or larger for output filtering and transient current supply (10V or greater rating)

Since you probably can't find an exact 1.46k ohm resistor you can use a 2k trimpot and adjust it to give the desired voltage. (connect the pot wiper to the cw end of the pot so the voltage will increase with cw adjustment of the pot wiper).

You might want to add a two wire connector to the camera connection so you can easily disconnect the regulator. A simple plastic connector such as they use in car wiring would be fine.

For the battery you can buy battery clips that attach to the battery terminals.

Any wire 20 gauge or larger should suffice.

Also need rosin core solder and a tube of rosin flux.

Double check your connections to make sure you wire the LM317 correctly. An incorrect connection can blow the device.

If you want to get fancy, you can put the board in a little electronic box. Otherwise just wrap the whole board assembly in electrical tape so it won't short out if it touches any metal.

Good luck.

__________________
Carl

 

Carl,

I just got back from Radioshack with all of my supplies except for the resistors. When I got there I got confused. First, there weren't any 240s, just 220s. Second, there were several different ones with different current capabilities. I wasn't sure which one to pick. And third, you completely lost me with the 2k trimpot part. Can you explain a bit more? Thanks!

Drew

 

Hi Drew, it's email Tom.

The '2k trimpot' is a variable resistor that can go from about 0 Ohms up to 2000 Ohms. The 'trim' means that it's usually used to calibrate your circuit once and then to be left alone (and resides on the circuit board, thereafter unseen by the user.) The 'pot' is short for potentiometer, which is just a type of variable resistor you turn i.e a knob. For example, the volume control on a radio is just a potentiometer. Almost all knobs you turn are potentiometers. Do a google image search for the various things mentioned and you'll get the idea.

As for the LM317, you already know that the output voltage is determined by the resistors used.
The LM317 is ubiquitous, but you can get regulators that give a predetermined output and thus need no external components. For example the popular regulators LM7805, LM7809, LM7812 etc. will output 5, 9, 12 volts respectively. You see the naming convention.

Look at this online LM317 calculator,

LM 317 Calculator

If you want to be spot on then simply use your 220Ohm resistor as the first resistor and the trimpot as suggested (small variable resistor) instead of a fixed value second resistor. Using your voltmeter, turn the trimpot until you get your desired output voltage.

Also the camera probably has its own voltage regulation, so you don't have to be spot on. Batteries aren't.

I was going to do something similar (though not month-long) time-lapse. Never followed up on it, but just realised my Canon TC-80N3 Timer remote controller already does never-ending intervalometry. Are you going to use Nikon's equivalent? Anyway, regarding the power, I think you're wise to not go via the AC inverter route.

 

Tom,

Thanks very much. So now I have an idea of what I need. My last question is which resisitors, 1 A, .5A, .25A, etc? Basically, which drawer do I get them out of?

Thanks.
Drew

 

Are those the max. current ratings of the available resistors, or did you mean 1W,0.,5W,0.25W (Watts), in which case they're the power dissipation ratings?

The resistors for the LM317 are just for setting the desired voltage and don't pass a lot of current, so you're safe with the the common 0.25W types.

For resistors, the power dissipated is

P = current*current*resistance.

Current in amps, and resistance in Ohms.

The LM317 will be the thing dissipating the most power, which is why the datasheet should be consulted: google 'LM317 datasheet'. The section 'Absolute maximum values' is of initial interest. The power dissipation is

P=current*voltage drop.

There's nothing to worry about in your case, this is largely academic. The high power spikes only occur very briefly when a photo is taken, otherwise the current drawn is tiny.

 

Watts is was. Sorry about that. Alright, off to Radioshack for hopefully, one last trip.

Drew

 

Hey everybody,

I have now fully assembled my camera with the voltage converter in the middle. Unfortunately, the camera will not fire off multiple images in a burst. After one, sometimes 2 frames, the camera turns off. The power supply doesn't quite hold up enough. I tried increasing the voltage a bit but that didn't work. I am wondering what I need to do to solve this. I am guessing it needs a larger capacitor but would like some more input...

Thanks!

Drew

 

Is the Lm317 definitely putting out the correct voltage? What is it meant to be anyway, 6 x 1.5 = 9volts?

Camera's operating normally with batteries? Everything wired up correctly? the battery compartment of my camera looks a little complicated.

Perhaps the camera really does instantaneously draw more current than the regulator can provide, which is at least 1.5Amps. Maybe the solution would be a regulator with a higher max current rating. To be honest I would be surprised if it really needs much more than 2Amps.

Don't know about a capacitor, regular AA batteries work without anything fancy. You're using a 12volt battery which provides a smooth voltage level.

 

Everything looks good to me and works fine with just a battery. The bottom of the battery pack says 9.5 V and 2.5A. When I was testing, I didn't try to fire any bursts but I never saw anything near 2.5A. It barely got to 2A. I am now wondering if its the frame bursts that gets the currents up to 2.5A.

The way I powered the camera is by soldering wires into the tray that normally holds the AAs. Therefore I don't really have to deal with which contact is which in the compartment.

The trimpot is set perfectly. When I hook everything up with a multimeter in place of the camera, the voltage is set perfectly at 9.5V. I hook the camera in and I can fire frames singly but when I try to fire multiple frames the camera shuts off like you had pulled the battery. Sometimes the shutter even stays open and the camera produces an error.

So do I need to look for a higher rated regulator? Any suggestions?

 

Sounds like it's drawing more current than the regulator can supply. You can try increasing that regualtor output capacitance.

How many frames do you need to fire in a row? Since it works for a least one frame, I would multiply the present output capacitance by the number of frames you want, to get the capacitance you need.

There's no particular limit on how large the capacitance can be.

__________________
Carl

 

I googled 'external power dslr'

http://www.danielmccauley.com/datash...8vsupply01.pdf

Nothing outlandishly profound, but evidently it worked for him.

 

One frame is minimum. Ideally I could pull in 5 image bursts with a period in between. For example, 5 frames are fired in order to compensate for high dynamic range (5 frames with slightly different exposures and then later combined), then we wait at least 10 seconds and take another burst. I'll try the capacitor solution and check out the link as well.

Thanks guys.

Drew