Making fresh use of old HID lamp reflectors using led corn lights

I assume I am not the only person with reflectors no longer being used. It didn’t bother me too much, because I kept improving on the older ones. Lately, I’ve decided to expand my Flowering capabilities. I need a Male room and a small staging area for small plants going into Flowering.

The Male room is what it sounds like, a place to put flowering males to prevent accidental pollination. The small area is where I intend small plants ready for flowering to spend a week or 2 while waiting for larger plants to get done and free up space in the regular Flowering room.

Naturally, I started thinking about lighting. Any new lights I put up are going to be LED, they also don’t need a ballast. Buying a bunch of LEDs is going to be very costly, otherwise I’d already have my Flowering room converted.

The best way to make use of a light is to provide reflecting surfaces to channel the light where you want it. I kept coming back to my reflectors sitting in a corner along with much other unused growing equipment. 2 had been there for more than 5 years. 1 was in use for a few years as a light in my clone box. And I have the 42" umbrella reflector that has the same plug end. I had made a light fixture years ago to put a regular size bulb socket to use a cfl for cloning. The conversion obviously was to need 110V electricity instead of the HID ballast. No big deal, I had everything I needed to do that without spending any money. I decided to do that again for the 2 remaining reflectors. When I went to Menards to buy the supplies, it turned out to be $16-20 (per lamp) in parts, plus an hour or 2 making them. This seemed like a lot for what I was doing. I put off buying the stuff for a while.

Then, I decided I want a minimum of 100W corn bulbs for the Male room. The catch here is that 100W and above seem to all have the larger base, a Mogul (E39), instead of the medium base (E26 or E27, same size as a normal household bulb). So, I actually needed one reflector to retain its bulb socket so I could screw in a large bulb. This requires re-wiring the larger socket with a normal 110V, 3 prong plug.

I decided to see if I could find an adapter to convert the ballast plug to a 3 prong 110 plug. No one makes such an animal, yet. I did find an adapter to convert a Sunlight Supply (my reflectors/ballast) cord to fit a HydroFarm ballast. I found this item at Amazon.

As a pkg of 2, it is cheaper than the 4-5 other cords available there. I didn’t look at eBay. I chose plugs from Menards that were simple and hold tightly. With these, there is no guessing as to how far back to cut the outer insulation. It opens all the way up from both sides, much like gull wing doors on a sports car. These were $4.99 each and look like this:

Notice the inserts in the clamping end. Top right is how the plug is setup when you get it, with the 2 arcs making an oval shape when closed. The bottom right shows the black plastic inserts turned over, exposing a rectangular shape with rounded corners. This is the position you want them in to close up on. The oval opening isn’t big enough for the large size cord it will clamp down on. It will still close tightly on the cord, but this way, you won’t injure your wrist tightening it.

I decided to convert these into adapters for 110V, this thread is to show how I did it. Many of our handy members may find this too much of a breakdown. Those members probably don’t need this thread. This is specifically targeted to members that would like to do it themselves but don’t know where to even start. So this is a step by step, illustrated, tutorial.

The purchased adapter:

This image show a side view as well as a straight down view at the ends.

Where to cut:

The end with the pins sticking out is the side I cut off. The female side will plug into the SunLight Supply style grow light cord. I apparently deleted the photo that showed it getting with a tin snips. All 4 adapters have been converted, so I can’t re-take it. But the photo shows the location to cut from. This spot will leave you the most cord to work with. With the plug ends I chose, this isn’t a big deal. Most plug types need the cord fed in through the clamping end, then you need to pull through as much as you can to work with and you’ll want all the extra cord you can get.

Cut away outer insulation:

I chose a box knife for this. You’ll want a good inch removed. Remember to make shallow cuts to find the depth of the insulation. It is very easy to cut through the wire insulation if you use too much pressure.

Strip wire insulation:

Strip away about 1/2" of insulation on each wire. Use a wire stripper for this. If you use the same adapter as I did, the wires are 16 gauge, your stripper should have a stripper hole marked for this size.

If you twist the piece of insulation as you are stripping it away, the stranded wire ends will twist nice and neatly together and make it easier to work with.

The wire pockets:

The arrows show exactly where to insert the end of the wires. They go between the 2 metal contacts. When tight, they provide a vise tight grip on the wire.

Tightly affixing the wire ends:

The photo shows the correct position of the wire colors. It is also embossed on the “doors” where the black, white and green wires go.

Close it up:

Once the wires are tight, swing both “doors” closed. There will be a small gap that will pull tight with the screws.

If you are worried about stripping the plastic holes while tightening You can use a ratchet clamp or a c-clamp, or even a vise to close it the remainder of the way. If you hold it by the very end, the screws can be tightened before releasing the clamp or vise you used.

Finished adapter:

All done. It took me about 15 minutes for the first one and about 10 minutes for each subsequent one. Under an hour to make 4 adapters. If you have never done something like this before, the first one, they may take you longer.

Ready to test it:

The adapter is affixed to the lamp socket cord end, a 120W corn light with an E39 (Mogul) base, 110V extension cord.

Testing it:

I didn’t want to blind the camera by showing the entire light, but you can see, It is running off wall power now, not a ballast.

Adapter for medium base:

If you buy a corn light 80W or below, you’ll probably get it with a medium (common household) base, like the 30W in the above pic. There 2 views of and adapter to allow a smaller bulb to fit the larger E39 bulb socket. These were $1.99 each at Menards.

How will it look with these giant bulbs in these reflectors? Have a look:

This shot is with the lamps off so you can see how well these bulbs fit. I was quite surprised to find ample space in the reflector for these bulbs. They are much larger than a metal halide, yet there is space all around the bulbs. Also note, the bulb on the right is a 50W with a medium base. I appears that teh size is almost the same between the 120W and the 50W. The only difference is the 120W is longer to accommodate the heavier driver and the internal fans. The 120W fits nicely into the shorter hood as well. I believe several of the 150W corn lights are also the same diameter and would fit. Anything larger would need more space, like, say, an umbrella reflector where the bulb mounts vertically. I intend to try a 300W in my umbrella, they put out a hair under 40,000 lumens. It will be interesting to see.

You may be wondering why I chose not to just re-wire the lamp socket with a 3 prong cord. It would have been cheaper than making the adapter. The benefit here is, if necessary, all I need to do is remove the cord adapter and it is back to an HID lamp. No muss, no fuss.

In any given community there are very handy folks and folks that rely on others to do a special thing like this. Maybe one of the latter will look at this and think, I can to THAT. I KNOW you can. Good luck! :smiley: :thumbsup:

EDIT: Oops, I forgot this last photo. The one showing the lamps lit.


Nice work re-purposing the reflectors!

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@Northern_Loki, I can’t tell you how often I’ve looked at them and wished I could get some value other than corner filler. For auxiliary flowering space to handle abnormal over flow, the corn lights should work fine. I used two corn lights to keep a Durban male flowering until it was out of flowers and it seemed fine.

I doubt if I can replace my 750W HPS with even a 300W corn light, I haven’t noticed anyone else using them here, so they are probably not as efficient as LEDs made for growing. The beauty of the adapter is when I try it, I just unplug from the ballast, put on the adapter, change the bulb, plug the adapter into the timer. If I don’t like it, it is an HPS again in 2 minutes. No significant loss of Flowering time.


Very clean & nice documentation. :thumbsup:

Have/can you measure their intensity?

What did the 120w lamp cost?




Thanks, @cannabissequoia. I used to train people to operate and eventually setup CNC machines that had very often had little background machining. I got used to being very detailed.

No, I have to trust the makers info until I see for myself. I have a decent light meter on my Amazon wish list, but it low in my priorities because my kid’s getting married 11/5 and I need to give that top priority for now.

I can measure the surface operating temperature. It is about 85° F and cools rapidly as I measure farther away. Heat is a major problem in summer months. My basement rarely gets below 85° during the hours the HPS is on

$88.75 at Amazon Warehouse damaged pkg deal. You can get some insanely good deals like that. This is 40% lower than most prices I could find. The outer box was scuffed up. The box inside, the one that gets seen on a display shelf, was totally unharmed as were the contents. I’ll take that kind of deal all day long. :slight_smile:


I know this is an older thread, but it seemed like the best place to ask. Will something like this work with 300W LED Corn lights? Looking at using 2 of them in my area.

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I think those are intended to be vertical & it’d be a waste. :thinking: :bulb:


Cool peek back thread!

Of course today, a color selectable (soft white 3000K, cool white 4000K, or daylight 5000K) 300 watt led can be had for $25, compared to a $88 120 watt damaged box lamp not even 2 yrs ago.

@WMoon518 Not a bad idea at all.

No, that’s 300W “Equivalent” It’s only using about 30W. What I am talking about is a 250W or 300W Corn that is equivalent to 1000W HPS(?) and is like 21000 lumens. They are like $100 or higher.

I don’t know. Seems to me, with having LED’s on all sides (well I guess it really doesn’t have side, more like all around it) it would reflect off of the “wings” wouldn’t it. My concern was that you couldn’t just “wire a plug” to it and screw in the Corn.

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