[fault151]

Am i right in thinking, when addint the heatsinks to the board, you use the sticky pads and a screw and bolt to secure the sinks? I have read the amb site about installing them, i just want to make sue i interpreted it correctly.

I take it, its the same process for installing off board sinks too?

 

[akione]

Quote:

Originally Posted by fault151 /img/forum/go_quote.gif Am i right in thinking, when addint the heatsinks to the board, you use the sticky pads and a screw and bolt to secure the sinks? I have read the amb site about installing them, i just want to make sue i interpreted it correctly. I take it, its the same process for installing off board sinks too?

The sticky pads are for mounting the mosfets to the heatsinks. they're required to isolate the mosfets electrically from the heatsinks.

The heatsinks fasten to the board with 2 screws at the bottom. They will need to be tapped to take whatever screws you use.
There is also a variation of the heatsinks, which have two pegs at the bottom, which can be soldered to the pcb, but most
people use the screw fix ones, I think.

For off-board sinks you're on your own really, as it all depends on what sinks/case etc you use.

 

[fault151]

ok so in the case of the b22 i need to use screw taps to mount them to the boards. When you stick the mosfets to the heatsinks, do you need to put a screw through them?

 

[Pars]

You should be using some TO-220 mounting kits such as Standard Products - Mounting Kits. The important part besides the insulator pad is the nylon shoulder washer, which insulates the screw from the device tab. The pictorial on the link I gave you should help as well. Mount the device to the heatsink, then put the heatsink on the board, before you solder the part in. This will help ensure that you get nice flat contact between the device and the heatsink. Ratshack sella a similar kit BTW.

 

[akione]

Quote:

Originally Posted by fault151 /img/forum/go_quote.gif ok so in the case of the b22 i need to use screw taps to mount them to the boards. When you stick the mosfets to the heatsinks, do you need to put a screw through them?

Hi fault151,

Sorry, I couldn't reply earlier ....... different time zones

I think Pars has sorted you out, though.

Thanks Pars.

 

[amb]

If you're using the default board-mount heatsinks, it's optional to isolate the MOSFETs from the heatsinks because the 'sinks are individual. You just need to take care not to allow the heatsinks to touch each other or to the case. When mounted directly without isolation pads (smear some heatsink compound to the mating surface), you get slightly better heat transfer.

 

[fault151]

Cheers guys, i have a better understanding now. The diagram in the link really helped. I think i'll use the isolating pads and do it as shown in the diagram.

Id like to use the big heatsinks like naaman used in his power supply for mine. I guess that would need insulating with the pads as it is one large unit. How do you support the weight of the off board heatsinks if it can't touch the case? Would it not put stress on the joint and board?

 

[amb]

If you isolate the MOSFETs then a common, shared offboard heatsink can, and should be mounted to the case.

 

[fault151]

Right i see. So if i used something like these, how would i isolate it to the case?

heat sinks

 

[amb]

If you isolated the MOSFETs from the heatsink, then you don't need to isolate the heatsink from the case. Just fabricate your own mounting brackets or drill and tap holes to the bottom of the heatsink for mounting to the case.

 

[fault151]

Quote:

Originally Posted by amb /img/forum/go_quote.gif If you isolated the MOSFETs from the heatsink, then you don't need to isolate the heatsink from the case. Just fabricate your own mounting brackets or drill and tap holes to the bottom of the heatsink for mounting to the case.

Ok thank you for that. I'll isolate them and mount them on brackets.

Thanks for your help, that cleared a lot of confusion!

 

[MrMajestic2]

I finally finished building my headphone/speaker switch that I ordered from Olimex. Its not yet tested in my B22, but at least it switches

It has four Omron G2R-1-DC5 that can handle 10A each. It also has integrated Zobel network for the speaker outputs.

Dont ask me about a schematic, because I dont have one. This is all done by hand.

 

[fault151]

Quote:

Originally Posted by MrMajestic2 /img/forum/go_quote.gif I finally finished building my headphone/speaker switch that I ordered from Olimex. Its not yet tested in my B22, but at least it switches It has four Omron G2R-1-DC5 that can handle 10A each. It also has integrated Zobel network for the speaker outputs. Dont ask me about a schematic, because I dont have one. This is all done by hand.

Nice one mate, looks cool! Hope it works all ok with your b22. Did you create the board design yourself? Or is it a kit?

 

[MrMajestic2]

Quote:

Originally Posted by fault151 /img/forum/go_quote.gif Nice one mate, looks cool! Hope it works all ok with your b22. Did you create the board design yourself? Or is it a kit?

Thanks

Its my own design, but the board was manufactured by Olimex.

 

[fault151]

Does anyone know which way the led goes on the power supply board? Theres no markings.