{"id":6036,"date":"2010-10-31T20:04:45","date_gmt":"2010-11-01T01:04:45","guid":{"rendered":"http:\/\/www.olino.org\/us\/?p=6036"},"modified":"2015-12-31T16:29:09","modified_gmt":"2015-12-31T15:29:09","slug":"practical-measurements-on-a-12v-dc-dimmer-used-by-olino","status":"publish","type":"post","link":"https:\/\/olino.org\/blog\/us\/articles\/2010\/10\/31\/practical-measurements-on-a-12v-dc-dimmer-used-by-olino\/","title":{"rendered":"Practical measurements on a 12V DC dimmer used by OliNo"},"content":{"rendered":"

\"\"<\/a>When OliNo measures lamps working on 12 V DC and these lamps are dimmable, then it as a 12 V DC dimmer available to use.<\/p>\n

This dimmer is put between the 12 V DC power supply output and the lamp itself.<\/p>\n

It appears that this dimmer uses a pulse width modulation (PWM) to switch the voltage to the lamp between a high level and a low level; this at a speed invisible to the human eye. It is a very efficient way to adjust the average level of the voltage that is output to the lamp.<\/p>\n

This article gives a number of measurements on the output of the dimmer to show what the dimmer does with the voltage to the lamp.<\/p>\n

<\/p>\n

Measurement setup<\/h3>\n

The dimmer is placed between the output of a 12 V DC power supply and the lamp that is normally fed with this 12 V DC.<\/p>\n

By adjusting the position of the knob the output voltage towards the lamp can be adjusted. For an impression see the schematic below.<\/p>\n

\"\"<\/a><\/p>\n

Scheme of the dimmer in the line from 12 V DC output of power supply and the lamp.<\/em><\/p>\n

Measurement results
\n<\/em><\/h3>\n

In this setup a led lamp has been connected to the output of the dimmer. The dimmer was connected to a 12 V DC output. The know has been set to different mechanical positions, and the V+ out and V- out at the output of the dimmer is measured and screenshots of the oscilloscope are given.<\/p>\n\n\n\n\n\n\n\n\n\n
Dim position<\/th>\nVoltage over V+ out and V- out<\/th>\n<\/tr>\n
100 % (no dimming)<\/p>\n

A constant voltage of 12 V DC is measured at the output of the dimmer. So the lamp is fed with a constant voltage of 12 V DC.<\/td>\n

\"\"<\/a><\/td>\n<\/tr>\n
75 % dim position.<\/p>\n

The voltage output to the lamp varies between 8 and 12 V DC. It is about 30 % of the time at 8 V DC and the remainder of the time at 12 V DC. One cycle of 8 V and 12 V takes about 1\/600th of a second, meaning that the voltage variations that result in illuminance variations of the led, will not be visible by the human eye.<\/td>\n

\"\"<\/a><\/td>\n<\/tr>\n
50 % dim position<\/p>\n

The voltage varies between 8 and 12 V DC. 50 % of the time at each value, every 1\/600th of a second.<\/td>\n

\"\"<\/a><\/td>\n<\/tr>\n
25 % dim position<\/p>\n

The voltage varies between 7 V and 12 V DC. It is 75 % of the time at 7 V and the remainder of the time at 7 V. The total cycle time of one time the 7 V and 12 V output is 1\/600th f a second.<\/td>\n

\"\"<\/a><\/td>\n<\/tr>\n
12.5 % dim position<\/p>\n

The voltage varies between -2 and 12 V DC. It is 90 % at 02 and the remainder at 12 V. The cycle time is 1\/600th of a second that a cycle of -2 and 12 V is output to the lamp.<\/td>\n

\"\"<\/a><\/td>\n<\/tr>\n
8 % dim position<\/p>\n

The voltage varies between -5 and 12 V DC> It is 95 % at -5 V and the remainder at 12 V. One cycle of -5 V and 12 V on the lamp takes 1\/600th of a second.<\/td>\n

\"\"<\/a><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

The dimmer uses pulse width modulation (PWM) and at high amount of dimming the voltage to the lamp is even getting negative. The cycletime of one cycle is 1\/600th of a second which easly can result in a flickering illuminance output of the led, however it will not be visible for the human eye.<\/p>\n

Dim measurement results<\/strong><\/h3>\n

The tested lamp is well dimmable. The voltage swings at the output of the dimmer , applied to the lamp, result in the following illuminance, power and power factor as function on the dim-position of the knob.<\/p>\n

\"\"<\/a><\/p>\n

Dim measurement results with the 12 V dimmer before a led lamp with MR16 base<\/em>.<\/p>\n

The results given above show that the efficacy increases a lot (normally a an led is more efficient at lower currents because of less internal heat and hence lower internal temperature). To zoom in more on the area 0 – 100 % see the image below..<\/p>\n

\"\"<\/a><\/p>\n

Dim measurement results more in detail<\/em>.<\/p>\n

The illuminance Ev is well selectable depending on the position of the mechanical knob. The range for the illuminance Ev is from 0 – 100 %.<\/p>\n

The power (this is the power of the lamp INCLUDING the dimmer) reduces more quickly than the reduction of the illuminance, resulting in an increased efficacy.<\/p>\n","protected":false},"excerpt":{"rendered":"

When OliNo measures lamps working on 12 V DC and these lamps are dimmable, then it as a 12 V DC dimmer available to use. This dimmer is put between the 12 V DC power supply output and the lamp itself. It appears that this dimmer uses a pulse width modulation (PWM) to switch the […]<\/p>\n","protected":false},"author":4,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[12,23],"tags":[68],"_links":{"self":[{"href":"https:\/\/olino.org\/blog\/us\/wp-json\/wp\/v2\/posts\/6036"}],"collection":[{"href":"https:\/\/olino.org\/blog\/us\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/olino.org\/blog\/us\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/olino.org\/blog\/us\/wp-json\/wp\/v2\/users\/4"}],"replies":[{"embeddable":true,"href":"https:\/\/olino.org\/blog\/us\/wp-json\/wp\/v2\/comments?post=6036"}],"version-history":[{"count":3,"href":"https:\/\/olino.org\/blog\/us\/wp-json\/wp\/v2\/posts\/6036\/revisions"}],"predecessor-version":[{"id":23799,"href":"https:\/\/olino.org\/blog\/us\/wp-json\/wp\/v2\/posts\/6036\/revisions\/23799"}],"wp:attachment":[{"href":"https:\/\/olino.org\/blog\/us\/wp-json\/wp\/v2\/media?parent=6036"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/olino.org\/blog\/us\/wp-json\/wp\/v2\/categories?post=6036"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/olino.org\/blog\/us\/wp-json\/wp\/v2\/tags?post=6036"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}