Blue LED Transilluminator




This instructable describes how to make a blue LED (470nm) transilluminator for DNA imaging using SYBR safe dyes. The transilluminator has a 6 x 7 cm viewing area for small agarose gels.

The transilluminator can also be modified to sit beneath the mini-gel electrophoresis tank (from a previous instructable), as described in Step 8. Used in this way, you can also visually track progress of your DNA during electrophoresis.

Open source hardware kit - This is an open source hardware project. To enable users to make or modify the device, I have included all of the PCB design files, enclosure design files and list of all hardware and electronics in a zip file attached below. We have also put together an LED Transilluminator Kit containing all of the parts described in this Instrucatble. 

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Step 1: Kit Contents

Each blue LED transilluminator kit comes with the following parts:
  • Printed circuit board and electronics: DC jack, resistor, switch and 72 x blue LEDs
  • Laser cut parts: 6 x black acrylic parts, 1 x clear acrylic parts, 1 x LED diffuser, 1 x blue light filter and an amber lid
  • Enclosure hardware: 4 x male-female standoffs, 4 x 3/4" long standoffs, 4 x 1" long standoffs, 8 x screws and a mini-screwdriver
  • Power supply. 12V power supply with an output current of at least 0.25A. Optional addition to the transilluminator kit. We use one from Jameco Cat # 252824.
Note: A complete list of all of the parts for the enclosure and PCB are included in the zip file in the previous step.

Step 2: Soldering the Components Onto the LED Board

Solder the following through-hole components onto the LED Transilluminator PCB. Note: for an Instructable on soldering components onto circuit boards, check out How-to-solder (Steps 4& 5) by noahw.
  • 72 blue LEDs. Positions D1- D72. Make sure to check the orientation of the LEDs before soldering. The cathode of the LED is indicated by the flat edge on the silkscreen of the PCB. Insert the LED so that the short leg (cathode) is nearest the flat edge in the silk screen. See image.  
  • 5.6 Ohm resistor. Inset the resistor into either R1 or R2.  
  • DC jack. Insert into position P1.
  • Switch. Insert into position SW1.
Once all the components are in place, plug in the 12 V power supply and switch on the board to check all of the LEDs are working correctly.

Step 3: Assembling the Enclosure Bottom

Before starting assembly, peel off any of the paper backing from the laser cut parts. 
  • Take the enclosure base and attach the four small male-female standoffs using four of the screws
  • Place the PCB onto the 4 standoffs and screw in the 1" standoffs
  • Take the four threaded studs and screw them all the way into the 1" standoffs
  • Place the enclosure sides, enclosure back and enclosure front parts onto the enclosure base. Note that the four parts have short tabs on one side and longer tabs on the other side - place the parts so that the shorter tabs go into the base plate with the longer tabs are at the top
  • The enclosure back part with the cutouts should fit over the DC jack and switch as shown in the images.

Step 4: Assembling the Enclosure Top

Place the next 4 laser cut parts in the following order:
  • First: Light diffuser film (2 sheets)  
  • Next: Blue filter 
  • Next: Black enclosure top (with the square cutout)
  • Last: Clear enclosure top (with engraving) 
Edit: A list of all of the acrylic materials used in the enclosure and the filters are listed in the file "BOM_enclosure.txt" in the "enclosure" folder of the zip file (see Intro). List includes suggested vendors and part numbers.

Step 5: Assembling the Amber Top and Testing

  • Screw the 4 remaining 3/4" standoffs onto the enclosure
  • Place the amber lid on top and secure in place with the 4 remaining black screws.
You have finished assembly of your transilluminator ! To test the transilluminator, plug in the power supply and switch it on. 

Step 6: Preparing a SYBR Safe Agarose Gel

Materials and Equipment
  • Mini-gel electrophoresis tank or similar
  • 1% agarose in TAE buffer (e.g. Melt-n-Pour Agarose, Carolina Biologicals, Cat # 21-7085)
  • 1 x TAE buffer (e.g. diluted from 50x stock from Carolina Biologicals Cat # 21-9033)
  • SYBR Safe DNA gel stain (Invitrogen Cat # 915548)
  • Tape 
  • Micropipette
  • DNA samples
  1. Seal the ends of the gel tray with the tape and place the gel comb in the slots of the gel tray. Place the tray on a flat surface.
  2. Melt the agarose in the microwave and let stand to cool until the bottle is warm enough to hold. Pour 50 mL of agarose into a small beaker.
  3. The SYBR safe stain is a 10,000 x stain. For 50 mL, add 5 µL of SYBR safe stain. Swirl the beaker to mix.
  4. Pour the agarose into the gel tray and let it cool and set (10 mins at room temp)
  5. Carefully remove the tape from the ends of the gel
  6. Place the tray in the tank filled with buffer
  7. Carefully remove the gel comb
  8. Pipet your DNA samples into the wells
  9. Place the lid onto the tank and connect the electrodes using banana cables
  10. Run the mini-gel at 50-100V. This takes approximately 30-60 mins.

Step 7: Viewing the Gel

Once the gel has finished running, take it out of the tank and place it onto the transilluminator. Switch on the LEDs - you should be able to see your DNA. In this image I have loaded 10-20 µL of a 1Kb DNA ladder (NEB QuickLoad, 50µg/mL). 

Step 8: Viewing Gels During Electrophoresis

The transilluminator can be easily modified to use used with the mini-gel electrophoresis tank to view DNA during electrophoresis. 
  • Unscrew and remove the amber filter
  • Unscrew and remove the 4 x threaded studs
  • Place the 4 screws in each corner to hold the enclosure together
  • Replace the clear tank lid with a lid cut from amber acrylic. Alternatively, place the amber from the transilluminator on top of the clear lid
  • Place the transilluminator under the gel box. You should be able to see your DNA bands shortly after they have run into the gel.



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    25 Discussions


    Question 1 year ago

    Great project! Where can I buy the acrylite 668-0 blue filter? Acrylite doesn't have it in stock anymore. How important it is to be of the same specs?


    3 years ago

    Thank you very much. Your project is great. I wonder if you can tell me what led do you use because I've tried standard blue leds (I think they are 465-470 nm) and it wasn't enough to see SYBR green.

    Anyway, thank you


    3 years ago

    Dear jorodeo
    Thanks for yuor fantastic instructions.
    I made a blue led transilluminator like yours. But its doesnot work!
    I stained dna with syber green and it glue under uv light but dose not under blue led light. What do you think?!
    How I can fix this problem?


    4 years ago on Introduction

    Electrophoresis Dna Fingerprinting
    - We are specialized in Gel Documentation System and we also focus on Electrophoresis of DNA and Electrophoresis DNA Fingerprinting.
    visit here :-


    5 years ago

    This is a great idea! I've been wanting to build an LED based illuminator for a while now. Especially for sub-cloning and gel extractions.
    We currently use A hand held UV light which can damage DNA and myself, so this 'ible is a much safer and effective tool.

    dear jorodeo,
    please follow the link and kindly let me know why this blue led transilluminator is optimized for varied stains where as why not the model you have specified.

    Srinivas J


    6 years ago on Introduction

    It looks great. We're looking at getting something like this to replace EtBr+UV and it looks perfect. Except for the size. Do you have any plans to make a slightly larger one? (For 10cm gels)


    6 years ago on Introduction

    Hi jorodeo,
    congratulations to this instructable of yours. It is excellent, as the previous ones.
    I have a question about DNA staining with SybrGreen. Apart from obvious health safety, are there any technical advantages or pitfalls, when compared to conventional Ethidium Bromide staining?

    1 reply

    Reply 6 years ago on Introduction

    Hi Isacco,
    That is a really good question. From what I know, the safety concern with ethidium bromide is really the big difference. In addition, UV can damage DNA which is not good obviously for cloning, sequencing etc. Having said that I used ethidium bromide for donkeys years in the lab and only recently switched to Sybr safe as I am no longer in an academic lab with access to endless piles of disposable gloves and convenient hazardous waste disposal.

    As far as technical advantages and pitfalls, I should note that I use Sybr safe, not Sybr green. From what I have read from the literature, Sybr safe is reported to have a comparable sensitivity to ethidium bromide. I use the gel stain version - add it to the agarose before microwaving etc. so technically it handles very similar to ethidium bromide. I did notice that you can't re-use the gel though, which I have done with ethidium bromide gels. So far I haven't any problems with using Sybr safe. Cost is about $0.70 per gel versus pennies (?) for ethidium bromide. I would say it comes down to what you have access to in terms of waste disposal, type of transilluminator etc. and downstream application of your DNA where the advantages of not exposing your DNA to UV may be important.

    I hope that helps !


    6 years ago on Introduction

    Great !
    I often see DNA with 254/302 nm UV transluminator and Etbr
    I want to have one but I 'm in Vietnam
    What materials of Blue filter ? Can i use blue arylic?

    2 replies

    Reply 6 years ago on Introduction

    Hi qmap,
    I have another instructable on making a UV transilluminator for this purpose ( which works really well. However, as ethidium bromide and UV are not the friendliest tools to work with (especially in educational settings) I also wanted to make a blue light/sybr safe version.
    For the blue filter, I tried a couple of different materials looking for something that can be laser cut and is not too expensive - this is blue acrylite # 668-0 which I bought online from, part # 5C028GT.
    I have just edited the enclosure bill of materials (found in the zip file in the Intro) to include a list of all of the acrylic with vendors/part numbers.
    By the way, if you want a kit, I'm sure we can ship to Vietnam ;)


    6 years ago on Introduction

    Many people will not appreciate the utility of this post but I'm so glad Instructables featured it in the newsletter. Our lab uses nucleic acid gel electrophoresis every single day so needless to say this peaked my interest.

    This is a GREAT and thorough instructable, thank you for sharing! Great to include Sybr Safe dyes. I hope we can adopt this to replace our $20,000 "Gel-Doc" and out-dated Ethidium bromide dyes.

    One addition I would make is an imaging system for record keeping. Have you seen the Berkeley made DIY Gel Doc? I built one up for our institute and it became pretty popular.

    Beth Israel Deaconess Med Ctr. Boston

    2 replies

    Reply 6 years ago on Introduction

    Hi ghwhitcher,
    Thanks for your comments ! Agree on the gel documentation step. I had seen the Berkeley DIY gel doc which is very nice, very cool that you built one. We are thinking about making an enclosure for this transilluminator with a camera mount and software for capturing and processing images. Do you use any image analysis software with your system such as ImageJ ?


    Reply 6 years ago on Introduction

    We use the free Canon software called EOS Utility which includes Remote Shooting when the camera is connected to the computer by USB. You may be familiar with it as it was recommended in the Berkeley build.

    EOS Utility comes free with Rebel cameras which is what we used for our GelDoc. Its getting harder to find (I think it doesnt come with PowerShot cameras) and not easy to download for free so it seems you usually have to get hold of a real disk.


    6 years ago on Step 6

    1. How do you run the gel at 50-100V using only a 12V power supply?

    2. Could you recommend a source for DNA ladders?

    3 replies

    Reply 6 years ago on Step 6

    Hi mhb,
    Good catch. I left off the electrophoresis power supply in the list of equipment !! I am still using the Whatman Biometra Model 125 low voltage power supply that I bought from Labrepco for $50. It has an output range of 50, 100 or 125 V. It is pictured on the mini-gel electrophoresis kit instructable. We are looking into an open source power supply for electrophoresis -- hopefully that will be the next Instructable !

    I can recommend the DNA ladders from NEB ( I have also used the ladders from Promega but recently switched to the NEB QuickLoad 1 Kb DNA ladder for convenience and cost. I recently ordered catalog # N0468S, which with shipping came to $82. Not very cheap, so I use it sparingly :)

    Good luck.


    Reply 6 years ago on Step 6

    Thanks. I just found a lower cost alternative ($46) from Thermo Scientific (


    6 years ago on Introduction

    I'd really like to see on the first page what an instructable's ultimate goal is and maybe a short video on what this does and why we want to build it.

    No, it's not obvious to us and No, I'm not picking on this in particular; most instructable's are not discernable as to what they do or what purpose this thing is used for which ultimately would decide whether we build one or not.