Salas hotrodded blue DCB1 build

[Salas]

No, if it clicks they are well. If they did not become swollen or something.

 

[BigE]

How did you arrive at 2.4A from 600mA? (not 600ma)

Are there not 4 devices each passing 600 ma? 4x600ma = 2.4 A no?

Or are you talking about mA? is mA not equal ma?

A simulation with Duncan Amp tools says that R ought to be 10 ohms.

 

[bullmout]

No, if it clicks they are well. If they did not become swollen or something.

It clicks . And no déformation . The dcb1 work Acctually with m'y aca i enjoy .
Just to finish the wiring , and solder the LCD to arduino.

Big thanks

 

[ghiglie]

I swapped the IRF/IRFP at the first soldering... I admit.

 

[Scorpion]

Hi all

Was wondering if it would be a problem to use some 49,9R resistors (measured at 49,8R with my meter) instead of the recommended 47R in th BOM ?

Just asking since I have NOS Holco H4 resistors on hand that I would like to use if possible...

Or, do I really need to go for 47R ?
Should I expect any differences in measurements should I go for the 49,8R ?

Thanks

Regards

Scorpion

 

[zonker92]

Also jumping in here, would this transformer work:

http://www.mouser.com/ds/2/410/VPT30-1670-224285.pdf

It says the secondaries can be wired in parallel for 15 volts output.

Thanks.

 

[Tea-Bag]

Hi all

Was wondering if it would be a problem to use some 49,9R resistors (measured at 49,8R with my meter) instead of the recommended 47R in th BOM ?

Just asking since I have NOS Holco H4 resistors on hand that I would like to use if possible...

Or, do I really need to go for 47R ?
Should I expect any differences in measurements should I go for the 49,8R ?

Thanks

Regards

Scorpion

Yes, close enough - but you may want to save them for a more critical position, unless you got a lot of them.

 

[Scorpion]

Yes, close enough - but you may want to save them for a more critical position, unless you got a lot of them.

Yes...meaning yes, no problem ? Like it will not affect much measurements (if it does, what should I expect/look for) ? Don't have to save the Holcos H4 for somewhere else. They are the closest value to 47R that I have but, if 47 is really what's needed, I'll order some.

Btw Tea Bag, I received the boards. Thanks A LOT for everything !! Really, very much appreciated !!

Was out for the last two weeks (vacations) and didn't spent much time on DIY...so again thank you.

Will also post some more pics tonight on the "Salas DCB1 resistor tryouts" thread.

Regards

Scorpion

 

[Tea-Bag]

It's close enough here. Measure the V+ and v- when you are done and we can see where we are. This is a 6% variance I think, which is just outside of what a carbon comp resistor might measure in either direction +/- if used.

Thanks for the kind words.

 

[Tea-Bag]

Also jumping in here, would this transformer work:

http://www.mouser.com/ds/2/410/VPT30-1670-224285.pdf

It says the secondaries can be wired in parallel for 15 volts output.

Thanks.

Looks fine!

 

[BigE]

I am stuck, and don't know if I am right/wrong....

I've used 3 ohms for the load in Duncan amp tools, and created a CRC, with a 0.5 ohm resistor between the two 4.7m caps. Starting with an 20.58 unloaded 216 VA transformer, this give 18 volts across at the output of the CRC which I think we are looking for, but 6 amps over the 3 ohm resistor.

I don't know how this relates to the DCB1 as it is a much different beast.

Can someone shed some light on this?

 

[Salas]

There is current sink alternative load in the Duncan. Use one at 0.6A.

 

[BigE]

ok thanks! A fresh look at the board layout, it looks like only the 600 ma goes through that 3 ohm resistor on its way to the shunts?

 

[BigE]

With the existing transformer, a 10 ohm resistor will drop the pre-pregulated voltage to 18 volts. If I use Duncan with a plain capacitor, the pre-regulated voltage is 24 volts.

FYI: the DC output is 10.01 and 10.02 at this time.

 

[Salas]

ok thanks! A fresh look at the board layout, it looks like only the 600 ma goes through that 3 ohm resistor on its way to the shunts?

That resistor sets the CCS its not any kind of load. The load to the raw DC feed and any filter combined is the active CCS itself. That constant current burns off in the shunts in its turn.

 

[BigE]

Thanks! That makes things a lot clearer... I have been clearly confused about how this circuit works.

When using Duncan, it is sufficient for the voltage across the CCS load to be between 17 and 20 volts, but higher will also work; using a straight C filter gives 24 volts across the 600 ma current sink.

I think I understand this better. It is not possible to replace the CCS load in Duncan with a resistor, since a resistor is not a CCS. The 3 ohms has nothing to do with the load, except to set the value of the CCS.

 

[Salas]

Higher will also work but gives a sinking penalty because more DCin-DCout times 0.6A in Watt will be burned across each CCS MOSFET. Has a moderate benefit on parasitic capacitance but not to go after it at such dissipation levels.

 

[BigE]

and the internal temperature is?

max continuous AC current = VA / Vac when feeding a resistor.
Max continuous DC current = VA / Vac / 1.414 * de-rating factor when feeding a capacitor input filter through a bridge rectifier.
The manufacturer will tell you the de=rating factor for that transformer. Expect it to be ~0.7
This results in a max continuous DC current of ~ half the max AC current.

You must check the manufacturer's data on how to use their product.

I have a 80ma 2x18vac secondary transformer (running at 600ma, the secondaries are measured at 17.5 V RMS).

These calculations result in:

VA/vac = 4.4, VA/vac/1.414 * 0.7 = 2.2 amps DC.

The manufacturer specifies the MAX current output to be 2.25 amps.

Does this mean 2.25/1.414 = 1.6 is the actual max DC current that can be safely delivered? or is that maximum just 2.25/1.414 * 0.7 = about 1.125 amps?

 

[zonker92]

Also jumping in here, would this transformer work:

http://www.mouser.com/ds/2/410/VPT30-1670-224285.pdf

It says the secondaries can be wired in parallel for 15 volts output.

Thanks.

Looks fine!

Thanks, Tea-Bag!

So I haven't started my build yet, but I'm thinking of just building it Stage 2 (I think, around 600MV, right?) and being done with it. I have one shiny new Mills 3R5 12W resistor lying around and I could buy a second one. Otherwise, I am using the big bag o' parts from Tea-Bag. I'm going to build a custom chassis with tons of air underneath (it will be on legs in an open cabinet, with a ventilated cover) and the base plate is going to be a large perforated aluminum sheet that's 1mm thick. Transformer will be 50VA 15+15.

Based on some other builds I've seen here, if I bolt the hot bits down to the bottom plate and maybe add some heat sinks to the bottom plate adjacent to the hot bits, I'm thinking I could probably keep the temperatures OK. Any thoughts on why this is a bad idea? Thanks.

 

[BigE]

You're going to attach the hot bits to some perforated steel? Not a good idea -- very poor heat transfer.

You'd do better to attach them directly to a heatsink that is standing upright, then throw the whole thing into the perforated case.