8Vdc & 1K dummy load is only 8mA.
That is 64mW, why 5W dummy load?
A 200r would draw 40mA & dissipate 320mW, just about right to get a 600mW resistor pretty hot.
Keep adding 200r (or 220r) until you find that the voltage drops below 8Vdc.
What is the maximum output current when the reg falls out of regulation?
How does that compare to the demand you think you have?
That is 64mW, why 5W dummy load?
A 200r would draw 40mA & dissipate 320mW, just about right to get a 600mW resistor pretty hot.
Keep adding 200r (or 220r) until you find that the voltage drops below 8Vdc.
What is the maximum output current when the reg falls out of regulation?
How does that compare to the demand you think you have?
So here's where I'm at - and thanks in advance for taking the time you all do to help us noobs. When I drop in a 180R 2W dummy to tune the 18v regs, all is well (save the adjustment changes need to the pot to dial it in to 18v). I can even drop in the 80R2W, and it'll supply the needed current with my build.
I also checked the current draw on the DAC IV I'm powering, and it's ~100ma (though I'm reading this with the loop on my meter; not sure how accurate it is), as reported. When I hook up the reg, I get the same thing - red led's don't light up. This DAC/IV (made by eXD) has a shared ground plane between the DAC & the IV; don't know if that's contributing to this behavior.
I'm tempted to hook it up, let it run, and try to adjust in place. Not sure where to go from here; seems I have a good reg but it doesn't work in circuit.
I also checked the current draw on the DAC IV I'm powering, and it's ~100ma (though I'm reading this with the loop on my meter; not sure how accurate it is), as reported. When I hook up the reg, I get the same thing - red led's don't light up. This DAC/IV (made by eXD) has a shared ground plane between the DAC & the IV; don't know if that's contributing to this behavior.
I'm tempted to hook it up, let it run, and try to adjust in place. Not sure where to go from here; seems I have a good reg but it doesn't work in circuit.
I've tried it with and without. Since I have narrow pins on the board for powering the DAC/IV, I've soldered 2 wires to the very head of the connector - using one for power and the other for sense. When trying to run 'senseless', I've simply connected both wires per pin to the appropriate shunt connector.
My thinking may be inherently flawed here, but it seemed soldering both wires to the head of the female pin connector would provide the proper resistance sense. In thinking about it though, it's not exact.
My thinking may be inherently flawed here, but it seemed soldering both wires to the head of the female pin connector would provide the proper resistance sense. In thinking about it though, it's not exact.
I am simulating the circuit in Proteus and trying to understand why you are using a 1R resistor on the base of the BC550C. The current flowing there is in the nA area and hence also the voltage. In simulation there is no sigificant reduction in noise on the output before it reaches 100 ohm. Can it simply be omitted?
I have it there as reserve compensation position in case of an odd load. For curtailing the OLG 0 point with a higher value as band aid. Less bandwidth is less total noise integration also. For self noise purposes when using the normal BW I kept it near zero. 1 Ohm used is for not to bother forming wire for a jumper. It could be a jumper all the same.
100 Ohm maybe. Its a juggling act depending on specific load reactivity also. Layout issues stopper too. Its doing rather well for a biggish gamut as it is. There was careful balancing, subjective also. If you have it sounding worse than a 317 then there is something wrong with interfacing or EMI is abundant coupling over long sense runs. If all is well its "wow!" better than a 317. That's an easy test for all, mainly for the non techies. Its a wide bandwidth shunt reg not a series chip or a discrete passer, this one is as plug and play as a shunt goes, still look twice when applying.
Hi all,
I've just built 3 of the Salas BiB modules from the latest GB, 2 Irf +- and 1 Bjt based. These are to power twisted pear kit: a buffalo II dac and legato 3.1 IV (previously powered by placid HD's).
I have been working to 5v/580ma on bjt for the dac and 15v/300ma for each IV channel, shunting around 80/100ma based on previous measurements (from placids). The dac bjt is up and running and appears to be stable, all as you would expect.
The IV Irf shunts are not behaving as I would expect though. It is quite likely that I have got something wrong in the calcs as this was a bit of a learning curve for me, but anyway. At the moment I only have the resistors to test with a dummy load of 90r for each: 166ma load (not ideal but) and this all appears to work ok (all leds/correct V) and I measure r101 (8r2) and get 304ma (2.5v/8r2). However, on connecting to the legato, for both shunts, the out V drops to 2v and current out is at 0.
Would I be right to suspect that this is saying - 'not enough current' for the legato?
[An anomaly is that with the placid BP in, that will do a similar thing if too much current goes in (more than 100ma over), V drops to 6-7v]
Someone has already pointed me towards separating the two circuits (as Andrew T discusses somewhere here) and testing the CSS. Im have not looked in depth about where exactly to disconnect/short ATM, but I am not in a rush and will take time to understand it before attempting. I could try some other r101 resistors of course, but would like to understand what is going on before messing about. If I have made any errors in what I have said I would be very grateful to hear your comments.
Many Thanks,
Lucas
I've just built 3 of the Salas BiB modules from the latest GB, 2 Irf +- and 1 Bjt based. These are to power twisted pear kit: a buffalo II dac and legato 3.1 IV (previously powered by placid HD's).
I have been working to 5v/580ma on bjt for the dac and 15v/300ma for each IV channel, shunting around 80/100ma based on previous measurements (from placids). The dac bjt is up and running and appears to be stable, all as you would expect.
The IV Irf shunts are not behaving as I would expect though. It is quite likely that I have got something wrong in the calcs as this was a bit of a learning curve for me, but anyway. At the moment I only have the resistors to test with a dummy load of 90r for each: 166ma load (not ideal but) and this all appears to work ok (all leds/correct V) and I measure r101 (8r2) and get 304ma (2.5v/8r2). However, on connecting to the legato, for both shunts, the out V drops to 2v and current out is at 0.
Would I be right to suspect that this is saying - 'not enough current' for the legato?
[An anomaly is that with the placid BP in, that will do a similar thing if too much current goes in (more than 100ma over), V drops to 6-7v]
Someone has already pointed me towards separating the two circuits (as Andrew T discusses somewhere here) and testing the CSS. Im have not looked in depth about where exactly to disconnect/short ATM, but I am not in a rush and will take time to understand it before attempting. I could try some other r101 resistors of course, but would like to understand what is going on before messing about. If I have made any errors in what I have said I would be very grateful to hear your comments.
Many Thanks,
Lucas
My methodology is to leave the load resistor in place, assuming enough 'free' current, and jumper to the device itself, see if it powers up appropriately.
I've lost a few volts in one project, and it was oscillating. It did not drop as much as yours by percentage. if you have a scope you could try that.
I've lost a few volts in one project, and it was oscillating. It did not drop as much as yours by percentage. if you have a scope you could try that.
