How can I make my touch lamp LESS sensitive, especially to voltage spikes? - Page 1
Forum section: electronics / projects

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: November 21, 2015, 07:33:52 pm
content: I have reverse engineered my touch lamp's controller PCB, BigClive style.I have done my best to draw a DaveCAD drawing of the schematic based on the images I had. I used BigClive's trick of taking an image of both sides, and then flipping the image of the backside, layering it on the image of the top, and turning the transparency to about 50%. I love this technique.The problem with this touch lamp is that it does not like LEDs, or lower wattage bulbs. With LEDs, there is enough leakage to actually dimly light the LED lamp no matter what, and the LED lamp makes the touch lamp much more sensitive, and usually will shut itself off with the slightest bit of electrical noise, and will also tend to turn itself on with electrical noise. If I turn my fan to a different speed, it will always cause the lamp to register a touch. What can I do to make it less sensitive to electrical noise and work better with lower wattage bulbs? The COB is very likely the controller that gives three brightness levels on the bulb and does everything else in terms of sensing. Oh, I should add that I live in the US, so the supply is 120V 60hz.Thanks everyone!

author: sarepairman2
author_rank: Frequent Contributor
timestamp: November 21, 2015, 08:54:11 pm
content: try decreasing the antenna impedance and adding series resistance to the switching elementi would try the series resistance first

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: November 21, 2015, 08:55:14 pm
content: Quote from: sarepairman2 on November 21, 2015, 08:54:11 pmCould you please elaborate?

author: sarepairman2
author_rank: Frequent Contributor
timestamp: November 21, 2015, 08:59:39 pm
content: you load down the antenna or add some resistance before your bulb/led. this will dissipate energy as heati dont know enough about triacs to help you otherwise.

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: November 21, 2015, 09:04:24 pm
content: Quote from: sarepairman2 on November 21, 2015, 08:59:39 pmThe triacs are essentially just AC switches. I am wondering why it is more sensitive the lower the load though.

author: sarepairman2
author_rank: Frequent Contributor
timestamp: November 21, 2015, 09:06:48 pm
content: they have a leakage current that is significant probobly.*parallel resistance not series resistance, since it is a current leakage

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: November 21, 2015, 09:10:25 pm
content: Quote from: sarepairman2 on November 21, 2015, 09:06:48 pmThe 100ohm resistor and 180pf capacitor looks to be what caused the LED to light dimly when the lamp is off. Not sure what that part of the circuit is there for however...

author: Zero999
author_rank: Super Contributor
timestamp: November 21, 2015, 09:15:28 pm
content: Quote from: iamdarkyoshi on November 21, 2015, 09:10:25 pmIt looks like a snubber network but 180pF is too low but the decimal point could be in the wrong place.

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: November 21, 2015, 09:17:29 pm
content: Quote from: Hero999 on November 21, 2015, 09:15:28 pmJust checked and it looks like I messed up the code. it is 100nf.

author: eneuro
author_rank: Super Contributor
timestamp: November 21, 2015, 09:50:18 pm
content: Quote from: iamdarkyoshi on November 21, 2015, 07:33:52 pmI didn't know anything about this style and did the same, but when someone design from time to time double layer PCBs rather standard way to see at the same time top and bottom PCB from top view-you have to flip bottom image...it is quite obvious.. it is common style

author: edavid
author_rank: Super Contributor
timestamp: November 21, 2015, 10:32:34 pm
content: To make an LED bulb work, most people put a shunt resistor (which can be a small incandescent bulb) in parallel. You will have to experiment to find a shunt value that works well, but you could try a 5W bulb.

author: eneuro
author_rank: Super Contributor
timestamp: November 21, 2015, 10:53:15 pm
content: Maybe pure testing with Human Body Model could give better results after reading this, since while you have unknown IC on PCB connected to lamp base I guess rather dificult put this thing into circuit simulator?Fundamentals of Electrostatic Discharge Part Five -- Device Sensitivity and TestingWe need HV 100pF capacitor and 1.5k resistor to simulate human body touching this metal base?Interesting, what physics phenomenon is used in those touch lamps-human "charges" this lamp by touching, or person who touches this lamp is charged?

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: November 22, 2015, 12:21:05 am
content: Quote from: eneuro on November 21, 2015, 10:53:15 pmMine works by making the base "live" at mains voltage, but at such a tiny current. When you touch it, you have a parasitic ground, so tiny amounts of current flow from you to ground. Its enough to dimly light a string of LED christmas lights if I touch the other side of the string XD