Salas hotrodded blue DCB1 build

[merlin2069er]

do you mean that the CCS sets the current draw for the regulator circuit, or do you mean how to set the CCS current draw?

hmm, what I mean, is how is the 300ma current set.

 

[AndrewT]

look at a standard two BJT transistor CCS.
The resistor in the supply route has a Vbe across it from the control transistor.

The pass transistor is controlled by that second transistor.

A BJT has nearly constant Vbe over a wide range of Ic. This allows the resistor that is parallel to Vbe to see a nearly constant voltage and thus pass a nearly constant current.

The resistor sees a voltage and passes a current based on Vbe / R, eg. 620mV/ 220r ~ 2.8mA

The FET type CCS works the same way.
The resistor sees a nearly constant voltage and the FET passes that constant current to the load.
In the SALAS style, the voltage across the resistor is not from a second transistor.

The resistor voltage comes from the Vgs of the FET and the Vf of the LED string. Vgs of a FET is substantially constant over a wide range of Id.
Current is defined by [Vfleds-Vgs] / R, eg [(1.8*3)Vfleds-4.1Vgs] / 33ohms = 1.3/33 ~ 0.039A = 39mA

The supply transformer+rectifier+smoothing caps sees a near constant load of ~39mA + [the current through the LED string that runs initially parallel to the setting resistor and then to Ground].

 

[RichLund]

Nearly finished my DCB1, just waiting for a few bits.

Salas - is it ok to use 2R resistors in place of the 2 x 1R?

Cheers

 

[Salas]

Yes, its OK.

 

[merlin2069er]

Are these the right size for the PS section?

4700uf / 63VDC, MLytic® Audio Grade Snap-In, 30mm x 40mm

I'm going to order a few...

 

[RichLund]

Are these the right size for the PS section?

4700uf / 63VDC, MLytic® Audio Grade Snap-In, 30mm x 40mm

I'm going to order a few...

They are still too big. The caps need to be 25mm max diameter. You need the 40V version of those caps, if you can find them.

Unless you are absolutely commited to having Mundorf caps, Can I recommend the 4700uF / 63V, Nichicon KG Series, Gold Tune, 25x50 from PX:

https://www.partsconnexion.com/capacitor_ele_nichicon_kg.html

Or Panasonic TSUP are excellent PS caps.

 

[Nick77]

Isnt this Mundorf cap at partsconnextion a good fit?

https://www.partsconnexion.com/capacitor_ele_mundorf_snapin.html


MUNDORF-71841

4700uf / 40VDC, MLytic® Audio Grade Snap-In, 22mm x 30mm, 68 ESR (mOhm) 10 ESL(nH)

 

[merlin2069er]

I bought antek's 0512 transformers for my older (not blue edition) dcb1 buffer. I was going to use them for my blue edition, but I don't think they can power the blue edition buffers.

 

[Tea-Bag]

I bought antek's 0512 transformers for my older (not blue edition) dcb1 buffer. I was going to use them for my blue edition, but I don't think they can power the blue edition buffers.

depends on what kind of current your going for.

 

[Ed LaFontaine]

Omron G6H-2 12VDC relays

Greets,

In support of stuffing these boards I have started an interest thread in the Swap Meet to supply the Omron G6H-2 relays. Express your interest there.

It appears there is sufficient stock currently available. However they are no longer being produced.

Omron G6H-2 12VDC relays

Thanks for all

 

[knassiri]

Salas,

This is my first build so please bear with me. I'm a little confused with what I'm seeing printed on the board relative to the BOM. I see mur820 on the board but no mention of these rectifiers in the BOM. Is this the location on the board where I use the recommended mur840's for the 'stage 1' build?

 

[Rodeodave]

Yes, there (at the edge of the board) is where the bigger TO-220 style diodes go. The BOM lists MUR840 or MUR860, which are higher voltage versions of the MUR820.

 

[Tea-Bag]

Yes, there (at the edge of the board) is where the bigger TO-220 style diodes go. The BOM lists MUR840 or MUR860, which are higher voltage versions of the MUR820.

and importantly, higher current.

 

[knassiri]

Thanks guys.

 

[Rodeodave]

😕 I think the 8 in MUR820 is for 8A and the 20 is for 200V. 40 is 400V and 60 is 600V.

The datasheet suggests that they benefit from a heatsink, but I doubt that it's an issue at currents needed for the DCB1...

http://www.datasheetcatalog.org/datasheet2/c/0g2qhxh8rrj7kilisa8ed5gzfe3y.pdf

 

[knassiri]

Sorry for the rudimentary questions. Is the higher voltage of the MUR860's going to be an issue if I'm hotrodding to 200mA? These were the only values I could find that weren't back ordered.

 

[Tea-Bag]

Sorry for the rudimentary questions. Is the higher voltage of the MUR860's going to be an issue if I'm hotrodding to 200mA? These were the only values I could find that weren't back ordered.

It will be fine. They are just nice diodes. Lot of stuff uses them with low current.

 

[knassiri]

Great, thank you Tea-Bag. I went ahead and splurged for the naked Vishay's you referred to earlier in the thread. I ordered directly from Texas Components and was quoted a two week lead time. Curious to hear how the tx2575's compare to the Takman's that are in the board.

 

[rothay]

It will be fine. They are just nice diodes. Lot of stuff uses them with low current.

I'm looking to hot-rodded the mesmerize board to 600mA with MUR820. I'm looking to mount MUR820 off-board a thick aluminum plate beneath the board. Would there be any noise or performance issue running wires between the diodes and board?

 

[merlin2069er]

Hey,

I got my caps mkp-1837, so I mount these in these in the 100uf position on the top and bottom.

Just double checking...

Thanks,
JG