[GreenKeys] Use of Volpe Board

[E.]

What kind of a heatsink would you recommend for those big, honking, through-hole resistors ;o ???


> On Sep 6, 2019, at 8:28 pm, epvgk at limpoc.com wrote:
> 
> For people who are considering using this board to interface a TTY loop with a computer, and
> who don't already have an existing current loop, here is what I'm using. 
> 
> This power brick is kind of overkill but not too expensive, and more importantly to me at least
> is very RF-quiet, so if you do radio stuff too it doesn't produce much RFI at all. 
> 
> https://www.aliexpress.com/item/33039935845.html
> 
> You also need to limit loop current to (ideally) 60 mA for 14/15/28/etc type machines, so put
> it in series with a 20+ watt 2K resistor like 
> https://www.parts-express.com/2k-ohm-20w-resistor-wire-wound--017-2k
> (it will get hot, give it a heat sink or space to breathe!)
> 
> For 20mA machines you could use the same resistor but a 48VDC supply and probably be ok, if 
> the teletype doesn't already provide loop current. 
> 
> eric