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what is this antenna for?
Hi, I estimate length = 100m. It is a lambda/4 monopole (two together). So wavelength is about 750KHz. They are separated by about 5 metres. The near field of one monopole is 2D^2/lambda = 50 metres. -So, they are both in each others' near fields. Therefore, the antenna pattern will be...- onload
- Post #5
- Forum: Antenna & propagation engineering
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Powering LED light displays more efficiently.
Hello, RichS….reference your input from a few posts back... Please may I give an example of a single “Lamp” (there would be many lamps in a product). All LEDs and components would be very phsically close in a Lamp. Please may I initially hereby define a “Stick” to be a series chain of X LEDs...- onload
- Post #30
- Forum: Circuit design
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Powering LED light displays more efficiently.
Hi, I'm afraid i can't say who i work for..(for one thing, it would identify me and my boss might read my embarassing slip above about V versus I curves for diodes!) Suffice to say we have high sales volumes. Anyway, i was interested in the above post which said that varying LED brightness...- onload
- Post #21
- Forum: Circuit design
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Powering LED light displays more efficiently.
Hello, Thankyou for the advice about driving the NPN from a 555 timer. I presume this means that the LEDs are basically turning ON and OFF very quickly. I am wondering if their will be a visible flickering at the lower brightness levels? It is quite interesting that most posters have suggested...- onload
- Post #18
- Forum: Circuit design
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Powering LED light displays more efficiently.
Hello, Regards the linear circuit we are trying to get away from....unfortunately its inadequately demonstrated here but i cannot provide further deteil....you get the general idea that its linear and not a switcher:- http://i16.tinypic.com/47m9eoi.jpg In a typical display unit, there would...- onload
- Post #15
- Forum: Circuit design
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Powering LED light displays more efficiently.
Thankyou for these posts......i will view them as all i want is basically a Buck convertor (non isolated) with the LEDs as the load. The LEDs we have vary brightness linearly with voltage control.......the currently in use linear regulator circuit (which i want to get away from and use SMPS...- onload
- Post #11
- Forum: Circuit design
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Powering LED light displays more efficiently.
Apologies. Max current through the series chain of five LEDs is about 25mA.- onload
- Post #6
- Forum: Circuit design
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Powering LED light displays more efficiently.
Hi, RajeevCell, -the series chain of LEDs is basically the collector load with the NPN in common emitter arrangement. There is an emitter resistor. The circuit definetely works. I'll try and post it. I have it in .jpg form and also .png form. Have you any ideas about how i can post it here...- onload
- Post #5
- Forum: Circuit design
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Powering LED light displays more efficiently.
Dear Engineers, I am working with LED light displays. There is a series chain of 5 LEDs whose brightness must be controllable. This series chain is across a 24V DC supply. There is a series NPN transistor in series with the LEDs which "burns off" excess volts if the LEDs need to be dimmed. This...- onload
- Thread
- Replies: 37
- Forum: Circuit design
