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Mitutoyo objective lens coins
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rockycarter



Joined: 27 Jan 2017
Posts: 61
Location: Canada

PostPosted: Sat Jul 08, 2017 10:09 am    Post subject: ring light Reply with quote

I wanted to try a ring light on coins. Here is a couple of photos taken with a ring light mounted on a enlarger lens. The coin is in a 2 x 2 holder


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ray_parkhurst



Joined: 20 Nov 2010
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Location: Santa Clara, CA, USA

PostPosted: Sat Jul 08, 2017 10:39 am    Post subject: Reply with quote

Rocky...was this with the 40mm Angel Eyes? I have seen good result with these COB ringlights. Turns out the 50 mm has about 40mm ID, so mounts nicely onto a 40.5mm-52mm step-up adapter. Here's what it looks like:



The bulge in the shrink wrap is a limiting resistor. I plan to install a 12V jack but haven't decided on the right resistor value yet to get best brightness and color temp.
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rockycarter



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PostPosted: Sat Aug 12, 2017 4:58 pm    Post subject: Reply with quote

yes ray this is the light. Ray good idea put a resistor in the circuit. push the load through the light. that will definitely brighten the light. that is a good idea for sure. i may try that as well.
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mjkzz



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PostPosted: Sat Aug 12, 2017 6:50 pm    Post subject: Reply with quote

Using resistor is a bit wasteful as it generates heat. Use an active, adjustable voltage regulator/DC-DC step up device is probably better and you do not need 12V, a box of 4 AA battery should be good. Here is what I did. I think that the DC-DC device regulates voltage well, so even the voltage of your AA batteries drops, the output voltage stay the same (unless batteries are really used up), thus you maintain constant brightness till batteries are dead.
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mjkzz



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PostPosted: Sat Aug 12, 2017 6:58 pm    Post subject: Reply with quote

also, some Angels' eye has plastic cover that can further diffuse the light from COB ring.
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ray_parkhurst



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PostPosted: Sat Aug 12, 2017 7:27 pm    Post subject: Reply with quote

mjkzz wrote:
Using resistor is a bit wasteful as it generates heat. Use an active, adjustable voltage regulator/DC-DC step up device is probably better and you do not need 12V, a box of 4 AA battery should be good. Here is what I did. I think that the DC-DC device regulates voltage well, so even the voltage of your AA batteries drops, the output voltage stay the same (unless batteries are really used up), thus you maintain constant brightness till batteries are dead.


Yours is a better solution, but for one-off use the resistor works OK.

It would be nice to have a generic current source controller for these kind of projects.
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mjkzz



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PostPosted: Sat Aug 12, 2017 7:40 pm    Post subject: Reply with quote

Quote:
It would be nice to have a generic current source controller for these kind of projects.


You can use the VCM controller to control an LED instead of a speaker, then you have an LED controller with 4096 steps (theoretically) :-)
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ray_parkhurst



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PostPosted: Sat Aug 12, 2017 8:57 pm    Post subject: Reply with quote

mjkzz wrote:
Quote:
It would be nice to have a generic current source controller for these kind of projects.


You can use the VCM controller to control an LED instead of a speaker, then you have an LED controller with 4096 steps (theoretically) :-)


Excellent idea! I will give it a try.
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rockycarter



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PostPosted: Sun Aug 13, 2017 3:17 pm    Post subject: Reply with quote

mjkzz thank you for sharing. I very much enjoyed the article well done.
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rockycarter



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PostPosted: Sun Aug 13, 2017 3:32 pm    Post subject: Reply with quote

Here is how i did my cobb angel eye. I purchased a AC to DC converter at amazon.ca 25.00 Canadian. The power supply is 12 volt 5 amp max. I went to a hardware store purchased a dimmer switch along with a switch box. I also purchased a cheap power bar. I cut the power cord in half on the power bar. wired the dimmer switch and mounted it in the switch box. This way i can dim the light to what i want. Depending on the metal of the coin. I am photographing. I wired every thing together. The dimmer switch is a dial dimmer work perfectly. I can now use this power supply for lots of things i need. With a dial dimmer it is graduated. That way i record the setting for the various types of coins. Works perfectly for myself.
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mjkzz



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PostPosted: Sat Aug 19, 2017 7:00 am    Post subject: Reply with quote

thanks ray, just hooked VCM up to an LED ring of mine, worked beautifully, though not sure if 4096 levels of power is needed, probably 64 is enough. Good thing is it does not flicker at low power setting as it does not use PWM.


Here is a video showing how it works -- I was tapping on keyboard to change power level. Next week, I will try it with some bigger LED at 1A when they arrive.
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ray_parkhurst



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PostPosted: Sat Aug 19, 2017 3:30 pm    Post subject: Reply with quote

How high voltage can I apply to the VCM? Not sure how much I will need but 12V is not enough. I run 25V with a dropping resistor and it works well. I think they run at rated current without resistor at 13.6V, so I will need to supply that.
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rockycarter



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PostPosted: Sat Aug 19, 2017 4:47 pm    Post subject: Reply with quote

How high voltage can I apply to the VCM? Not sure how much I will need but 12V is not enough. I run 25V with a dropping resistor and it works well. I think they run at rated current without resistor at 13.6V, so I will need to supply that.

yes ray that is right. These lights run at 13.6 to 13.7 volts constantly.
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mjkzz



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PostPosted: Sat Aug 19, 2017 5:20 pm    Post subject: Reply with quote

I told them to put in caps made by Samsung and rated 50V, as I really do not trust Chinese made caps. The 7805 in the VCM can handle 30V.

Quote:
How high voltage can I apply to the VCM? Not sure how much I will need but 12V is not enough. I run 25V with a dropping resistor and it works well. I think they run at rated current without resistor at 13.6V, so I will need to supply that.


I think these Angels' eyes comes with a current limiting thing in metal casing, so I believe you should be able to drive it at 12V. I only needed about 8.3V for my mod with DC-DC step up setting to have enough light, even with a plastic cover. So if you use 25V, a lot of power is wasted as heat, probably more than 50%

The particular ring shown in video is arranged as 3 LEDs in series as a group, 10 groups and total of 30 LEDs. Each LED has forward voltage between 2.85V to 3V, so 12V should be enough for the VCM to drive it at full power
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