IKEA Jansjo LED Light Modification

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mawyatt
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IKEA Jansjo LED Light Modification

Post by mawyatt »

Some reference posts related to the LED use.

https://www.photomacrography.net/forum/ ... hp?t=41353

https://www.photomacrography.net/forum/ ... c&start=30

Had a IKEA Jansjo LED light clamp break, decided to look at the possibility of modifying the base to allow a standard photo 1/4-20 type mount. While looking into this we noticed the possibility of increasing the light output by replacing the LED module with a more powerful LED COB.

The Cree CMA1306 LED COB appears to fit the IKEA mounting holes, these have 800~1000 lumen output vs. the IKEA 220 lumen output. Of course power dissipation will be ~4X higher also, so pulsed operation may be useful, otherwise the Jansjo case likely will get too hot!

The Cree CMA 1507 or CMA1516 should fit but will require new mounting holes, or thermal adhesive to mount, the 1516 COB has ~2400 lumen and certainly will require pulsed operation, but has 10X the output :D

The CMA1507 has similar output to the 1306.

These Jansjo lights are nice and small, allowing close positioning with the "Goose Neck" but have limited optical output at a warm ~2700K. So the idea of using a higher power ~5000K LED COB inside the Jansjo case seems intriguing.

However, all these "options" require a different power supply, and to keep thermal management in order require a pulsed operation, so a custom controller/power supply is in order. This controller shown below operates in Current Mode with 4 LED Jansjo modules (more with paralleling) and provides support for the mentioned Cree LED COBs. Separate control for Continuous Modeling and Pulsed output is provided and can be controlled by ON-PCB or remote pots. Pulse output range is from 10ms to 1.2 seconds, but can be easily altered with a pot and/or capacitor change. Camera trigger input is also provided.

I'll be ordering these PCBs and components today, PM if interested.



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Best,
Research is like a treasure hunt, you don't know where to look or what you'll find!
~Mike

Scarodactyl
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Post by Scarodactyl »

This looks like a very interesting project. That said, and not to be lame, but it seems like a 150w halogen light source with a fiber optic gooseneck might be a sensible option at that point.

mawyatt
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Post by mawyatt »

Scarodactyl wrote:This looks like a very interesting project. That said, and not to be lame, but it seems like a 150w halogen light source with a fiber optic gooseneck might be a sensible option at that point.
Agree, actually that's a better solution! However, I don't have a 150w halogen source, and have 4 Jansjo lights (just broke one, the clamp cracked off, but the LED still works). I don't use these Jansjo lights for actual image captures much, since they are low in output and 2700K color, they do help as a modeling light.

Best,
Research is like a treasure hunt, you don't know where to look or what you'll find!
~Mike

ChrisR
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Post by ChrisR »

Looks good. It should be possible to place a lump of amluminum in the head..

I don't understand the circuit sysmbols eg at R20, R21, R22. They're not all pots... ??
Chris R

mawyatt
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Post by mawyatt »

ChrisR wrote:Looks good. It should be possible to place a lump of amluminum in the head..

I don't understand the circuit sysmbols eg at R20, R21, R22. They're not all pots... ??
Chris,

Yes, these are just various types of pots so one have a choice. Some can have proper knobs, others require a screwdriver, some multi-turn. Trying to make these circuits as flexible as possible for those that wish to DIY. You may note to the right end is a 3 terminal male header, this is so one could position a remote pot off the PCB and just plug it in.

Best,
Research is like a treasure hunt, you don't know where to look or what you'll find!
~Mike

ChrisR
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Post by ChrisR »

Ah :smt023 , I couldn't see why you'd use 3 pots in parallel !!

Could be a nice challenge for students to work out the result :)
Chris R

mawyatt
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Post by mawyatt »

ChrisR wrote:Ah :smt023 , I couldn't see why you'd use 3 pots in parallel !!

Could be a nice challenge for students to work out the result :)
Chris,

Yes, the timer would be a good circuit for your students to work out. The output current mode operation is more involved but not that difficult if you don't include dynamic effects, then you get into 3rd or 4th order functions.

A simplified analysis assuming an ideal op-amp with gain A shows the LED current is equal to the input op-amp voltage divided by the sense resistor + 1/(A*gm) or:

Iled ~= Vin/(R + 1/(A*gm))

Where Vin is the input pulse amplitude, A is the open loop op-amp gain and gm is the NMOS transconductance. Since A is very large (>100,000) and gm isn't very small, then 1/(A*gm) ~ 0 and:

Iled ~ Vin/R :D

Note the lack of dependance on anything other than Vin and R. This is in fact true to a 1st order as the supply voltage, LED characteristics, NMOS output conductance & threshold voltage, temperature effects and other undesirable effects get squashed by the op-amp open-loop gain. Of course if the sense resistor isn't accurate then the LED current isn't accurate!! Also, the sense resistor should have a low temperature coefficient for good temperature stability.

Anyway, this might be something to toss at your more advanced students if they have a fundamental understanding of op-amps and negative feedback.

Here's a few examples of various type pots that might be used, except the tiny surface mount which is too small for consideration. The blue are multi-turn types, the larger type Bourns 3590 has a dial for precision setting, Bourns 3296, Bourns 3266, the white is a single turn HDK VZ06 type. A Bourns 3386 is also supported but not shown.

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Best,
Last edited by mawyatt on Thu Apr 23, 2020 11:06 am, edited 1 time in total.
Research is like a treasure hunt, you don't know where to look or what you'll find!
~Mike

mawyatt
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Post by mawyatt »

The Cree LEDs arrived and I've configured a Jansjo LED lamp with the CMA1306 9V 700ma 1000 lumen LED COB.

It fits nicely and only required cutting the tabs off the reflector back with pliers, and drilling out the reflector to clear the larger Cree LED COB center cluster.

Then just solder the Cree COB in place, be sure to use some thread grease on the backside and mount the modified reflector, that's it.

The output is really bright and a beautiful white (5000K LED), not the yellowish orange 2700K of the original LED module.

Thermal seems good, I'be been running at 500ma @~9.2 volts and the case is warm but not too hot to the touch.

Still waiting on the custom PCBs, but think this mod and the custom PCB with pulsed capability will really augment the versatile Jansjo lamps for our macro use. I also have a few other Cree LED, one of which has ~2400lumen output and should also fit the Jansjo. This will require pulsed operation tho, since the power dissipation is much too high for the tiny Jansjo case.

Best,

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Edit: Just installed the ~2400 lumen Cree CMA1561 LED COB in a similar fashion, the reflector can't be used tho. Mounting required a couple small washers to "hold" the COB in place firmly against the Jansjo head base mount as shown. This LED COB extremely bright and with over 10 times the output of the standard Jansjo LED module. I can run this with about 150ma at 33.7 volts continuous (~40% output) without the case getting too hot to touch. The CMA1561 is rated at 400ma nominal at 2400 lumens, and 700ma produces ~3600 lumens. At max current of 1050ma the output is ~4800 lumens. So pulsed operation could produce peak outputs 3000~4000 lumens without much difficultly if the pulse width stays short.

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Quick test setup for Jansjo LEDs, top one had a clamp broken. Cut sides off the clamp handle then drilled a hole for 1/2-20 bolt and "T" nut. This works really well.



Best,

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Research is like a treasure hunt, you don't know where to look or what you'll find!
~Mike

mawyatt
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Joined: Thu Aug 22, 2013 6:54 pm
Location: Clearwater

Post by mawyatt »

The custom PCBs arrived and we assembled one of the Quad LED Controllers with parts that were on hand, still waiting of parts order. The PCB is 80 by 95mm, double sided standard FR4. Turns out we had equivalents for all the parts for use with the modified low voltage Jansjo Lamps, so no issues. No trace cuts or added wires required, just a couple component value adjustments to get the 1st PCB up and running :D

The current scale was setup for the Jansjo LED lamps modified with the Cree CMX1306 9V 700ma nominal 1000 lumen COB, these have a max current of 2400ma and produce ~200%, or 2000 lumens at 1600ma. Half the outputs were setup for 2 amps per volt scale factor, the other two were scales for 1 amp per volt.

Here's a couple quick images of the assembled PCB in testing, note the 3 wire pairs & connectors for the 3 Jansjo lamps. A low frequency test oscillator was used to "trigger" the circuit, simulating a trigger from a camera, controller or computer. Power was supplied by a Lab Type Supply to allow voltage and current monitoring and control during initial testing, later a standard power supply will be used.

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Here's a scope trace for a 100us pulse width of 1200ma peak LED current (yellow) and a photo-sensor (standard 6mm Blue LED with 47K shunt Resistor), Scope scale factors are 100us/div and 100mv/div Yellow, 20mv/Div Blue. Current scale factor for Yellow trace is 200ma/div

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Here's a scope trace for a 1000us pulse width of 1200ma peak LED current (yellow) and a photo-sensor (standard 6mm Blue LED with 47K shunt Resistor), Scope scale factors are 100us/div and 100mv/div Yellow, 20mv/Div Blue. Current scale factor for Yellow trace is 200ma/div

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Here's a scope trace for a 10ms pulse width of 1200ma peak LED current (yellow) and a photo-sensor (standard 6mm Blue LED with 47K shunt Resistor), Scope scale factors are 1ms/div and 100mv/div Yellow, 20mv/Div Blue. Current scale factor for Yellow trace is 200ma/div

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Here's a scope trace for a 1s pulse width of ~900ma peak LED current (yellow) and a photo-sensor (standard 6mm Blue LED with 47K shunt Resistor), Scope scale factors are 100ms/div and 200mv/div Yellow, 20mv/Div Blue. Current scale factor for Yellow trace is 400ma/div

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As these scope traces show the LED current has some leading edge ringing as predicted, this is due to the various parasitics and output NMOS FET "Miller Capacitance" for you circuit designers. However this ringing will have no effect on the LED output, and the current waveform looks good as does the actual LED optical output as sensed by the photo-detector, very pleased with the way these waveforms look on the scope.

Also the LED current is completely independent of the supply voltage once this voltage meets a level sufficient to supply the LED and current source, these scope traces were with a supply voltage of 18 volts.

Complete control of the LED peak current and continuous current is accomplished with the two pots in the center, pulse timing is controlled by the single pots in the upper left. Timing ranges are set by the Yellow jumper in the upper left and ranges from 100us to 10ms and 10ms to 1 second. Other ranges can be set by either changing the timing pot and/or the timing capacitors.

A quick test image captured at ISO 800 @ shutter speed of 1/160 or 6.25ms, with a white styrofoam cup diffuser and 3 modded Jansjo LED lamps operated @ 1200ma each produces a proper exposed test image with a pulse width of 6ms. Ambient doesn't play into this as a test image with the LEDs off produces a black image. At 1200ma each Jansjo is producing ~1600 lumens, so a total of 4800 lumens. At 6ms then the lumens seconds are 28.8, and with an ISO of 800 (the original base ISO is 64, not 100 as previously reported) then the effective exposure is (800/64)*28.8 or 360 lumen second equivalent. Thought this might require more exposure (more lumens or longer pulse width) due to the foam cup diffuser, but this was not the case.

Here's what the test setup looks like.

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Later I might do a quick video to show the operation.

Best,
Research is like a treasure hunt, you don't know where to look or what you'll find!
~Mike

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