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Hi guys. I read in another topic that Legato needs close to 300ma per rail at 15V rails. A bit less at 12V rails.
In the manual of Placid BP (writen when it was to power the analog rails of a Buffalo32S), it says "we will assume you are aiming for ±15VDC rails and ~200mA per rail load current".
But that is not the case anymore, since now it must power Legato.
So, my question is: How exactly should i configure the BP Placid? I know for voltage ~12V, but what current?
Thanks!
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It's hardly rocket science: the Placid is a shunted PSU, so you adjust the current to a little more than what you need. The Legato manual states a fairly constant 360mA current (I assume at 12V, as this is the recommended voltage), so adjust the Placid to something like 400mA.
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So, you say that i should adjust the CCS pots (VR1/VR2) until the measured voltage across R1 and R2 are ~ 0.40V, so that Placid
BP will be able to supply current of up to 400mA ?
Thanks for your help!
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Without the buffer i suppose it's around 200-250 mA? Anyway, the VR1/VR2 stop turning when i reach 0,70V (before the target of 0.25V) ,so i have a problem, what should i do? Should i use the other pair of VR1/VR2 (20Ω) that came with the BP Placid? Edited by user Sunday, September 26, 2010 6:32:51 AM(UTC)
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Quote: i should adjust the CCS pots (VR1/VR2) until the measured voltage across R1 and R2 are ~ 0.40V That is correct. If you've omitted parts of the Legato obviously you're going to use less current, so you'll want to lower the voltage across R1 and R2. By how much I do not know. The guidance says to shunt around 50mA, so if you use 200mA adjust the voltage to 0.25V so you supply 250mA. If the current supplied is too low you'll notice the voltage dropping considerably. 2nd: if you can't reach 0.25V but are stuck at 0.7V I think something is wrong with VR1/VR2. Also check the resistance of R1 and R2: they should be 1ohm. Switching to the other pair of variable resistors might be a good idea.
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Ok, thank you very much, understood!
Since i am listening directly from the buffalo outpouts for the time being and I'm not in a hurry, i will just wait for Russ or Brian to tell me what they think i should do regarding the VR1/VR2.
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So... can the designers please advise?
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ok, the answer came by email, thanks!
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