Sinedup
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SinedupNew Member
Joined:
Sep 16, 2015
Messages:
27
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Hi all. Have you ever tried to squint at miniature, faded, or generally hard-to-read screen printing on a device (think IC's, small glass diodes), or wish to record the part number and specs for ordering? Many cell phone cameras have a focal length of several cm. My Galaxy focuses to minimum of about 8-10 cm. Too close and image is blurred. A cellphone's camera and magnifying glass can serve as a temporary "macro-scope". In practice, I found that dark components such as IC's become too dark when shadow (from close 1-2 cm) magnifier/camera/hands block the light. Solution? Make a simple ring-light with a few U/B white LED's facing inwards. Dimmer can be added as too bright may over-expose photo. Alternatively, a flat device such as an IC or PCB can be scanned at high res on a flatbed scanner and saved/edited/auto-enhanced. A webcam has a very close focal length of about 5 mm, so could be used directly. Tip: construct a jig from plywood etc to hold cell (peep-hole for lens), magnifying "macro" lens, led's and screw-adjustable base for component. LED supply type is your choice. To save batteries, and as my workbench is next to the PC desk, I made mine 5V USB-supplied. To calculate dropper current-limiting resistor to series LED 'chain', subtract total voltage-drop (forward voltage Vf) of all led's led from supply voltage (Vf), then divide this by led forward current (If) in amps. This gives minimum resistor value in ohms. Formula: Rs Ω = (Vs-Vdtot)/If. Series-connected LED's have several advantages over parallel individual: Maximum Wattage rating of Rs is lower. Current (brightness) through series chain is uniform. Battery consumption is lower. Dimmer can be a trimmer, pot (watch wattage), hex-selected resistor array (binary incremented values), or adjustable regulator.
Joined:
Sep 16, 2015
Messages:
27
Likes:
1
Hi all. Have you ever tried to squint at miniature, faded, or generally hard-to-read screen printing on a device (think IC's, small glass diodes), or wish to record the part number and specs for ordering? Many cell phone cameras have a focal length of several cm. My Galaxy focuses to minimum of about 8-10 cm. Too close and image is blurred. A cellphone's camera and magnifying glass can serve as a temporary "macro-scope". In practice, I found that dark components such as IC's become too dark when shadow (from close 1-2 cm) magnifier/camera/hands block the light. Solution? Make a simple ring-light with a few U/B white LED's facing inwards. Dimmer can be added as too bright may over-expose photo. Alternatively, a flat device such as an IC or PCB can be scanned at high res on a flatbed scanner and saved/edited/auto-enhanced. A webcam has a very close focal length of about 5 mm, so could be used directly. Tip: construct a jig from plywood etc to hold cell (peep-hole for lens), magnifying "macro" lens, led's and screw-adjustable base for component. LED supply type is your choice. To save batteries, and as my workbench is next to the PC desk, I made mine 5V USB-supplied. To calculate dropper current-limiting resistor to series LED 'chain', subtract total voltage-drop (forward voltage Vf) of all led's led from supply voltage (Vf), then divide this by led forward current (If) in amps. This gives minimum resistor value in ohms. Formula: Rs Ω = (Vs-Vdtot)/If. Series-connected LED's have several advantages over parallel individual: Maximum Wattage rating of Rs is lower. Current (brightness) through series chain is uniform. Battery consumption is lower. Dimmer can be a trimmer, pot (watch wattage), hex-selected resistor array (binary incremented values), or adjustable regulator.
