Forum » Webinar Questions » Rotary Switches - Shorting Vs Non-Shorting

Rotary Switches - Shorting Vs Non-Shorting

Webinar Questions

Ask questions about webinar lessons here. To see the Previous Webinars for a complete list of archives tuning webinars. 

Page 1

Hi Guys

Hope you are all wellI'm looking at buying a couple of rotary switches for the project of fitting a PDU to a Porsche 928. Which application would the benefits of either Shorting or Non-Shorting Rotary Switches. the two I'm looking at are from Farnell and switches are below.Non-Shorting - 56SD30-01-1-AJN - Rotary Switch, 12 Position, 1 Pole, 30 °, 200 mA, 115 V, 56 SeriesShorting - 56SD30-01-1-AJS - Rotary Switch, 12 Position, 1 Pole, 30 °, 200 mA, 115 V, 56 Series

Could I have some guidance in to what switch to choose and some understanding of Non-Shorting Vs Shorting Please.

Regards Liam

Shorting = the two adjacent pins are temporarily shorted (connected) before the first is released (disconnected) --- "make before break" (also noted as MBB)

Non-Shorting = the first pin is entirely disconnected before the second pin is engaged --- "break before make" (also noted as BBM)

A shorting switch ensures that there is *always* a signal to the receiving brain box. During the short, the current will pass through the smaller of the two dividers (least resistance). If a non-shorting switch is used there is a "dead-zone" where no signal makes it to the brain. Non-shorting can cause issues if whatever you're adjusting is quite sensitive in its signal refresh rate. A good debounce code in the brain can take care of that (if you have access to such code/parameters) - but if there isn't any debounce in the signal you run the probability of signal instability (and momentary system chaos). That instability may not be a big deal in your system - it may be huge - especially if you're on the opposite end of your spectrum (say going from position 10 to 9 and 10 is max voltage vs not connected being zero volts to the brain).

If your application is strictly to support on/off connections (e.g. daytime running lamps + fog lamps + rally lamps) then it's likely irrelevant which you choose.

Hi Kenny

Thank you for your reply, I thought that was the case. I was just looking for reassurance. made the use a lot clearer thanks again.

One of the switches is for the exact reason of controlling the lights.

Much appreciated

Regards Liam