On Sunday, February 17, 2019 at 3:20:08 AM UTC-5, Sgitheach wrote:
>
>     
>
> The lite placer builds it in 10 minutes (I don't run it at full speed) as 
> against a few hours and serious back ache... So pre-fitted SMD parts is 
> going to be my preferred route.
>

Sounds good.
 

> Your other points:
>
> 1. The E1T needs two pulse inputs. One to reset the tube to zero and one 
> to step the tube forwards. The reset pulse is a a fairly brute force effort 
> and not hard to generate. The step pulse is more tricky requiring a 
> sawtooth waveform for a certain peak voltage, a defined rise time and a 
> defined decay time. 
>
> More info here:
>
> http://www.dos4ever.com/E1T/E1T.html
>

My footprints are all over that article 8-}

My E1Ts are of uncertain age and ancestry. Hopefully they all work. If not, 
I'll have to trade some NIMO tubes for working E1Ts/
 

> 2. The sleep options are to run the heaters at full power 24/7 or shut 
> them down completely when a set period of inactivity has been seen by the 
> PIR (the heater power choice and time periods are all user adjustable 
> without burning the firmware). I know there are various schools of thought 
> on extending heater life including keeping them simmering on low power. The 
> clock doesn't do the latter. My understanding is that the greatest risk to 
> the heater is when its resistance is lowest when fully cold and so the peak 
> current will be highest on switch on. So the 6.3V heater PSU slow starts 
> the output, taking 7 seconds to rise from 0V to 6.3V. If you want a slower 
> rise then it is not hard to change this period by changing single capacitor 
> on the main board. 
>

  That sounds like a good solution.
 

> 3) The selection of WIFI or GPS is made using a plug in board, both cannot 
> be fitted simultaneously. The the plug in board communicates with the SAM 
> using 3.3V TTL (not 5V!). So if you have an external NMEA source it is 
> trivial to feed that into the connector. I use the default 4800 baud speed, 
> another speed would require a trivial firmware change. I have designed (but 
> not built) a RS232 plug in board so that a wider range of external time 
> sources can be accommodated. 
>

I can probably provide 3.3V, but if there's an RS-232 board available that 
is probably a safer bet. 

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