Blueman2 Posted January 10, 2018 Report Posted January 10, 2018 Very cool! Congratulations on the build. And the Mechanical Engineer in me loves seeing that dainty little circuit in that massive bench clamp.
JoaMat Posted January 11, 2018 Report Posted January 11, 2018 Milled this today – negative regulator. Shot by USB camera approximately magnitude 20. Using a 15th end mill, minimum clearance between pads, traces etc. is 16th. There are 5 vias 12th and they actually hit the bottom pads quite accurate. CNC machine is a fantastic gadget 10
Pars Posted January 11, 2018 Report Posted January 11, 2018 Yes, that is fantastic work!Sent from my iPhone using Tapatalk
Kerry Posted January 11, 2018 Report Posted January 11, 2018 That's amazing that you can mill that board. Nice work ?
sbelyo Posted January 12, 2018 Report Posted January 12, 2018 does anyone have a GRLV + board to spare?
JoaMat Posted January 12, 2018 Report Posted January 12, 2018 Thinking loud. What if a simple CCS north of the 9 volt Zener as below? Will certainly make a tiny smd version layout looking cleaner.
kevin gilmore Posted January 13, 2018 Author Report Posted January 13, 2018 works fine, more diode switching noise gets thru. Also requires more voltage differential as that current source eats up about 4v.
luvdunhill Posted January 13, 2018 Report Posted January 13, 2018 works fine, more diode switching noise gets thru. Also requires more voltage differential as that current source eats up about 4v.What are 60Hz and harmonics down to with the stock design?
kevin gilmore Posted January 13, 2018 Author Report Posted January 13, 2018 way under a microvolt. pain in the ass to measure.
luvdunhill Posted January 13, 2018 Report Posted January 13, 2018 Hm, how way? -120dBV shouldn’t be hard to measure. -150dV, sure.
JoaMat Posted January 13, 2018 Report Posted January 13, 2018 9 hours ago, kevin gilmore said: works fine, more diode switching noise gets thru. Also requires more voltage differential as that current source eats up about 4v. LTspice indicates a need of another 3 V unregulated. Plus more diode switching noise. Still a golden reference device or is it a silver line thing?
sbelyo Posted January 14, 2018 Report Posted January 14, 2018 Is a 9+9 30 VA transformer enough to pull 9V DC from a GRLV?
cspirou Posted January 14, 2018 Report Posted January 14, 2018 36 minutes ago, sbelyo said: Is a 9+9 30 VA transformer enough to pull 9V DC from a GRLV? That would give you ~12V before regulation which is only a 3V drop. Seems to be to cutting a little close. 10VAC is a little more comfortable. also don't forget to change the lt1021 reference
sbelyo Posted January 14, 2018 Report Posted January 14, 2018 I'm going to connect a transformer to the mains to see what voltage it puts out. My mains are a little high so it might be 10V or a little over for the lt1021 reference, do I need the 5 or 7V ?
cspirou Posted January 14, 2018 Report Posted January 14, 2018 4 minutes ago, sbelyo said: I'm going to connect a transformer to the mains to see what voltage it puts out. My mains are a little high so it might be 10V or a little over for the lt1021 reference, do I need the 5 or 7V ? Definitely do that. I bought a 18v + 18v transformer and it's giving me 22v + 22v. I'll find the post but I think it's better you use 5v.
sbelyo Posted January 14, 2018 Report Posted January 14, 2018 (edited) for V+: ((R8 + R7) / R7) x 10 (reference voltage of D5 - LT1021-10) for V-: ((R9 + R10) / R10) x 10 (reference voltage of D7 - LT1021-10) If I use this calculation and all resistors are 1.5K like the silkscreen, then use a 5V reference I'd get 10V That'd work for me because I need 9-12 Vdc. Now I'll see what the xformer is putting out in the way of voltage. it's 10.96 Vac with no load so that should be fine pulling 9 - 9.25 Vdc @ 0.80 A right? Edited January 14, 2018 by sbelyo
cspirou Posted January 14, 2018 Report Posted January 14, 2018 Here it is: 10.96 VAC will give you a 5-6V drop before regulation. You should be okay. I suspect you don't want a voltage close to the reference because then you would need a much higher R7/R10 resistor, which would increase noise.
sbelyo Posted January 15, 2018 Report Posted January 15, 2018 With a 5V reference will the GRLV work with an output lower than 12Vdc?
mypasswordis Posted January 15, 2018 Report Posted January 15, 2018 Yes but I would rather go with a higher vac trafo and set it to 10Vdc output than hope that the pre-reg voltage is high enough using a 9vac trafo for 9vdc. If you really have to use the 9vac then there are any number of low noise LDOs out there to use
JoaMat Posted January 16, 2018 Report Posted January 16, 2018 As I understand LT1021 is used in shunt mode in GRLV. From datasheet I get the impression that the 5 volts version of LT1021 is not meant to be used in shunt mode. As I recall one builder once tried a LT1021-5 in a KGSShvPSU without success.
sbelyo Posted January 16, 2018 Report Posted January 16, 2018 I'm starting to think that I should use something else. I think it's better
mypasswordis Posted January 16, 2018 Report Posted January 16, 2018 Ah yeah forgot about that, it's in the very first paragraph of the datasheet that the 5V version only works in series mode. The TPS7 regulators that are used in the amb modules and Dynalo mini are rated to 1A and are LDO
cspirou Posted January 16, 2018 Report Posted January 16, 2018 Is the only thing keeping the GRLV from running effectively <10V the reference? In an earlier post I think Kerry mentioned using a LM4040 and those are available down to 2.048V.
mypasswordis Posted January 16, 2018 Report Posted January 16, 2018 I used the 4040 on one of my GRLVs so I didn't have to put in a separate order for the LT1021. It works but is noisier than the LT1021, not sure if it's audible though 1
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