what resistor for 445 diodes in parallel?

[norty303]

So, I'm going to ask the question thats just hanging out there, waiting to be asked...

If wiring in parallel is so much more fiddly, requiring more components, and greater risk of damaging all the diodes in the event of one failing (growing greater the bigger the build), why would you want to do this in the first place?

If its to keep overall currents required down, would the best compromise be pairs of diodes in series together (with appropriate resistor), and then parallel as many pairs as you need?

I think I'd be more inclined to just series wire up to the driver limit and then add another driver (and so on, etc)

[Doc]

Wait a minute....what?

Only multiple diodes wired in parallel do we need to put resistors in? Wired in series no resistors needed?

I'm going to borrow Andy's word. WTFook?

Correctamundo, the current in a series circuit is the same anywhere in said circuit.

The voltage in a parallel circuit is the same anywhere in said circuit (not counting
losses).

[Doc]

So, I'm going to ask the question thats just hanging out there, waiting to be asked...

If wiring in parallel is so much more fiddly, requiring more components, and greater risk of damaging all the diodes in the event of one failing (growing greater the bigger the build), why would you want to do this in the first place?

If its to keep overall currents required down, would the best compromise be pairs of diodes in series together (with appropriate resistor), and then parallel as many pairs as you need?

I think I'd be more inclined to just series wire up to the driver limit and then add another driver (and so on, etc)

That's how I've done my 445s using a 12v supply to the drivers, however no resistors are required.

[dnar]

So, I'm going to ask the question thats just hanging out there, waiting to be asked...

If wiring in parallel is so much more fiddly, requiring more components, and greater risk of damaging all the diodes in the event of one failing (growing greater the bigger the build), why would you want to do this in the first place?

Hi Norty. One simple answer. the choice to wire in parallel with a single driver is to avoid having to insulate the diodes, which simply moves to another set of challenges (electrical insulation while providing thermal conduction).

You simply trade one set of compromises for another. That is why case isolated diodes are a win-win.

You right, the perfect solution is 1 diode per driver, although that is more $$$, more adjustment, more space ra de ra de ra.

[Phredy1]

Hi Norty. One simple answer. the choice to wire in parallel with a single driver is to avoid having to insulate the diodes, which simply moves to another set of challenges (electrical insulation while providing thermal conduction).

You simply trade one set of compromises for another. That is why case isolated diodes are a win-win.

You right, the perfect solution is 1 diode per driver, although that is more $$$, more adjustment, more space ra de ra de ra.

Finally the light in my head turned on (and it was blue). Everything makes sense now. Thanks Doc and dnar for all the good advice!!!

[andy_con]

can someone help me?

i need some 1.1ohm resistors i can only seem to find 1k resistors.

can someone in the know hook me up with an ebay link?

[LaNeK779]

search for 1r1 resistors sir andy

but it is not a common figure

so either go for 1r or 1r2 (1.2 ohm), something around tge 2-3 watt mark
http://cgi.ebay.co.uk/2W-Metal-Film-...#ht_1781wt_905

or http://cgi.ebay.co.uk/10-x-1R-1W-1oh...#ht_1142wt_905


if you insist on 1.1 ohm, i found some, but only at 1/2 watt http://cgi.ebay.co.uk/10pcs-1-1-OHM-...4#ht_599wt_905

[andy_con]

umm suppose 1ohm will do but i only need 1/4 to 1/2 a watt.

will google them now, thanks for ya help

[LaNeK779]

in that case, try to get metal film resistors, they are smaller than the carbon film ones. and better quality

[andy_con]

just brought these

http://cgi.ebay.co.uk/ws/eBayISAPI.d...=STRK:MEWNX:IT