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1 channel dimmers


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The "original" Strand DIM-1s are good:




I've used them for conventional tungsten (Source 4's, Preludes and the like) and in switch mode for 4' UV tubes.



The Thomann ones look pretty much the same (although have 3-pin XLR), if these are the ones you mean:




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I haven't used those ones specifically but I have been involved in a few jobs with "mains dimmable" leds and my experience is that triac dimmers don't work unless you put a big load lamp on as well (500W). If you don't, the capacitance in the drivers causes the dimmer to latch on at full or flicker a lot.


Reverse phase (IGBT) dimmers work much better but are hard to find in a professional form. Sinewave IGBT doesn't work well because the driver relies on timing the switchoff point to determine the setting of the dimmer - you get a bit of dimming but only in the 70%-100% range.


With a reverse phase dimmer (depending on how the LED driver works) you can dim down to about 10%, but you can never dim them up from off - they always snap on at about 40%.

Also most of the dimming seems to be in the 40%-60% region of the dimmer.


Basically mains dimmable LEDs are not very good, avoid and use ones with a 0-10V or DMX control input if at all possible. I'm surprised the S4 mini LED doesn't have that option but it doesn't seem to.

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Very timely post this...





I have been watching but not joined until now.


I have a couple of old Strand lamps and wanted to control them.


I had toyed with the idea of a DIM1, but as other posters note, there are a couple of suspiciously similar items available from various suppliers (like CPC et al) , but the Strand one has the advantage of a BS546 socket and a wired remote fader, whereas some others don't.


I called up a Strand dealer in Bristol, and they told me that the units are all made in China.


Time meant I bought a Transcension UP-2 from CPC, also made in China. (It has 3 pin XLRs for DMX, and an onboard fader) but 90% looks the same as the DIM1


My observations about this unit are as follows, and if anyone can provide a comparison with (say) the DIM1 I'd be interested.




1 x 500W load (profile lantern)


1 x UP-2 unit




1. The dimmer law is very non linear from a perception perspective - the light comes on too early and is at perceived 50% brightness by about 20/100 and 95% brightness by about 65/100 on the unit fader. (I've not had a chance to try it with a DMX controller so I don't know what that behaviour might be)


2. 1% shift on the fader represents a noticeably flicker=step in output brightness on the lantern on mid range values, clearly something to do with the analogue > DMX > analogue converter electronics which provides the "last takes precedence" functionality.


3. Electronics - basic linear circuit (I think) feed-forward phase angle switching of a ~25A triac device, (no output power feedback)


I concede that the device was only advertised as "suitable for a follow spot", which typically isn't an integral part of a scene change, but it's somewhat disappointing really.


I was wondering if somehow the Strand one has a better piece of software in it to provide a more linear looking brightness profile (S Law or whatever). It's a shame, because clearly this device could work a whole lot better with some decent software....

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