As we all know, in India, one of the hot-selling items is the electric "mosquito repeller", or, to give it its proper name, the electric vaporizer for mosquito repellent. Every household has three or four--if not more-- of these units and most of them are kept on throughout the night. Most of these units consist of little more than a ceramic heater element and a neon tube or LED power-on indicator, the whole thing built into a plug-pack.
The lady in question, a brand new mother, wanted a dim night-lamp. The usual 'zero watter' was too bright for her liking and she said the mosquito unit's 'on' indicator was too dim to serve any useful purpose. This gave me the idea to replace the neon or the solitary red LED with a couple of hi-brite LEDs. Of course, we know that it is an easy matter to 'tailor' the brightness by choosing a suitable 'dropper' capacitor. I decided on a two-LED configuration in order to keep the assembly simple and at the same time make use of both negative and positive swings of the mains AC waveform. Just have a look at the circuit/s and the modifications.
First of all open up your mosquito unit--usually a couple of screws in the bottom secure the two halves of the shell together. Be careful to study the plug-pin unit and its mounting to the assembly while disassembling. You will see the ceramic heater and sometimes a 'protector' NTC device wired together directly to the plug pins. The neon or the LED too will be connected to the same points through a series resistor. Please note that the heater gets really hot and so soldered joints will not stay put, and the original connections will be twisted or crimped. Use a sharp cutter and cut away the indicator's series resistor, leaving a few mm of lead for us to 'twist-connect' to. Do the same thing at the other end too while cutting away the neon or the LED.
Now study the unit and plan how you are going to mount the LEDs. Usually they do not need any "mounting". You can follow the example shown and evolve your own method. I soldered together two LEDs back-to-back--that is joined them together with the + lead of one to the - lead of the other and the - lead of the first to the + lead of the second. This is how they looked, with one lead each left uncut for connection to the series resistor and the dropper cap/bleeder resistor combo, respectively.
This made it convenient to wedge the LED assembly to a vertical 'holder' moulding that originally held the neon indicator tube/LED. Check the photo for the details. This meant that ample insulation was also there between the leads and the LEDs faced up, throwing their light onto the ceiling. The diffuser of the unit does not "diffuse" the focussed LED beam that much, and I found that it was best to mount the LEDs facing up. You may try your own "trial and error" methods here for mounting/direction of the LEDs.
I chose a 0.1 uF/400V dropper capacitor and a 1k Ohm/half watt series resistor. After twisting and soldering the bleeder resistor onto the cap leads, check the "measurements" by placing the LED assembly, the cap etc into the shell and then cut the leads to give you enough to 'twist-mount' the parts. Crimp or twist one end of the dropper cap to the heater terminal lead stub (that you had left conveniently cut earlier). At the other heater terminal, crimp or twist-mount the 1 k Ohm resistor. Now mount the twin-LED assembly suitably and cut the leads so that you can comfortably twist the two ends of the LED assembly to the capcitor lead and the resistor lead on either side. The leads will be rigid enough to keep the assembly safely in position. Test by plugging in.
The LEDs should light up and the heater should heat up. Once everything is satisfactory, use minimum solder and solder up all the twisted connections to preclude oxidation of the twisted contacts over time. Reassemble the shells together carefully and you have a nice combo mosquito unit/night-lamp for the bed room or the child's room--or anywhere else you might want to have some dim 'romantic' lighting!
So get a couple of LEDs and resistors and a capacitor, and open up that mosquito unit -- ASAP!
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So get a couple of LEDs and resistors and a capacitor, and open up that mosquito unit and start the mischief in the bed room light-- ASAP!
ReplyDelete??? Is it not UKG
Paul
Whether the miss is chief or the missus is chief depends on a lot of factors, mostly not electrical, but necessarily high-voltage stuff!
ReplyDeleteBut the dimness/brightness of the light depends on the value of the capacitor.... ;-)