[GreenKeys] Use of Volpe Board

[Charles]

www.bigassfans.com
:)


-----Original Message----- 
From: E.
Sent: Friday, September 06, 2019 8:43 PM
To: Robert Downs via GreenKeys
Subject: Re: [GreenKeys] Use of Volpe Board


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
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