More than a year ago I was approached by an independent filmmaker about light dimmers. The problem fo them was how to get affordable light dimmers to control the film lighting. I was told that many independent non-commmercial filmmakers use a HarborFreight router speed control to dim the lights used for moviemaking. The reason is that they are are cheaper and far heavier (15A) than building our own from a 600W house lights dimmer. The problem with these router speed control devices is that they do not dim down enough to turn the lights off. They also don’t quite go to full brightness but that is a minor problem as they have a switch that bypasses the electronics and provides full power.
After some discussion I got one of these units mailed to me to see if there is a way to modify those to work as better light dimmer.First thing I did was to open the device to see how it was built out. Based on what I saw the circuit was pretty close to a traditional light dimmer. And there seemed to be also some adjustment trimmer for some adjustments. Looked promising.
The nest task was to test the device. The problem that those are designed to operate 110-120V AC 60 Hz power has a slight problem to me. In Finland the mains power is 230V AC 50 Hz. Getting real 120V 60Hz power and finding 120V AC light bulbs is hard here where I live. I got one 120V lamp with the router speed control device so I had suitable lamp. Getting real 60 Hz power would involve some expensive power converter or using 12V to 120V AC true sinewave inverter or something similar that I did not have at the moment. So I decided to do my first testing with 110V 50Hz power that I get easily with a suitable voltage conversion transformer (I used fully isolating transformer for safety).
I did some testing. I found that the controller trimmer potentiometer controls how dim the output can go. I was able to get lamp very dim. Here is the picture of the dimmer electronics with a well insulated screwdriver adjusting the trimmer (there is a hole on the circuit board that gives access to the trimmer). Well insulated screwdriver and isolation transformer powering the whole circuit makes it possible to do ajustments with live circuit pretty safely when you know what you are doing. I mailed the results back to person who sent me the router speed control and he tested the results with real 60 Hz power (they worked).
The adjustment instructions: Set the potentiometer lowest setting. Then adjust the trimmer so that you get as dim light as possible without noticeable side effects. When you set the trimmer to too low setting, turning potentiometer will cause the output to be completely off (lap turns off). When dimmer reaches this full iff state, the dimmer potentiometer need to be turned quite much (one third or one fouth) until the light turns back on, quite bright already. The ideal setting I think would be that the lowest dimmer potentimeter setting would just set the bulb to be just barely on (lamp filament dark red and does not make much light), so you have always full control range from it to full setting without problems.
In this way a relatively cheap router speed control device is converted to a relatively inexpensive high power light dimmer.
Sir,
I need to know abt your dimmer system for NVG lab and whether it is compatible or not.
Compatible with specifically what?
Tomi,
Thanks! I use these controls on some motors, but noticed that sometimes I could not slow thing down enough. Your tip on the internal pot that could be tweaked was very useful.
Cheers!
Mark
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That was spot on! I could not have done that better at all haha. Hate to admit it though
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Hello Tomi,
thank you for your post about the Router Speed Control.
I’m searching for a longtime for a 220v router speed control.
My question is off this speed control also useful is for 220v?
The factory says yes, see http://www.nb-dazhong.com/enprosoall.asp?mmm=3&sele=19&text=19&fl=Various
I hope you can help me.
Thanks Schummie.
I don’t know if this specific router speed control is also useful is for 220v.
The router speed control I receeived said in the box that only for 110V AC, and had USA power plug&jack in it.
The comment at http://www.nb-dazhong.com/enprosoall.asp?mmm=3&sele=19&text=19&fl=Various page
“The output voltage ranges from 100V to 240V” could mean that they have models available in those voltage ranges.
Maybe they have one model for 110-120V and other for 220-240V or so… That’s my quess.
Usually this kind of control circuits are just designed form one voltage.
It is technically possible to build the circuit that can handle the full voltage range, but it typically becomes more complicated.
And when with different voltages you always need two different products (different connectors), then when you have two
different models that have different connectors, then is no problem in changing few component values needed to adapt circuit
for different voltages. Or even optimize cost so that use lower voltage rated components (usually cheaper) for 110V model, and components
with higher voltage ratings for 220V model.
Hello Tomi,
thank you very much for your response.
I have a BOSCH Palm Router PR20EVS (Europe Bosch GKF 600) and this router has no speed control, in Europe they sell this Bosch palm router not with speed control.
I have problems to work with this router.
9 years ago I got a accident at my work. In the last 9 years I bin operated for 8 times and I have done a lot off rehabilitation but nothing wants to help.
The router speed is so high that it gives me a lot off pain when I use the router.
Therefore I’m searching for a speed control for my Bosch.
Does your speed control (from HarborFreight) on 220v?
Thanks for your help.
Schummie.
The speed control I have is model that is designed for 110-120V 60 Hz operation. It is designed for USA markets. It was sent to me from USA so I could check if it could be modified to that dimmer use. All it needed was some adjustment on internal trimmer.
I live in Finland where mains voltage is 230V 50 Hz. I tested that speed controller only with 110V 50 Hz power that I got from a transformer (I used both 230V-110V traveler converter and laboratory variac). I did not test that device with 220V, because I determined that 230V directly to it could destroy it.
I have not tested that with any router. I tested the controller only with light bulb to see how well it worked as cheap high power dimmer. And it worked for it.
I’m trying to find out what the best lighting is to make my property more safe at night. Are those solar powered lights worth it?
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