Connecting toggle switches to Bodnar card

[fordgt40]

Jack

The potentiometer is not rquired to be a specific value, as it acts as a voltage divider to give a varying voltage to the a/d converter. So it makes no difference whether it is 10k or 100k, it is the voltage difference which is important. I generally use 10k. There may be a reason why 2.7k is not suitable, but if I was you, I would adopt the empirical solution and try it first.

David

[Boeing 747 Flyer]

Thanks Daivd, but I'm worried incase I'll blow the card. Using Ohms law, we can take voltage (5) divided by resistance (2.7k) = 0.02 Amps, which is a fair bit of current.

[fordgt40]

Jack

Ohms law says:-

I (current in amps) = V (volts) divided by R (resistance in Ohms)

In this case I = 5/2700
= .0018 amps

There are probably other factors at play here, but too much current is not one of them

David

[Boeing 747 Flyer]

Hi David,

Thanks for your reply... Just to confirm, is the card current protected (eg incase 5V is shorted to ground for the pot input).

[fordgt40]

Jack

Sorry, but I have no knowledge of this card

David

[iwik]

Hi,
As David says 10k or greater is preferred as the more pots you connect across the ref supply the resulting resistence reduces and a limit maybe reached dependant upon where the ref come from. Please make sure you have the correct terminals connected. The wiper or USUALLY the middle terminal
should go to the input of the Board. The other two to 5v and grnd. If the moving contact of the pot is connected to 5v then when the pot is turned to max
there will be a puff of smoke from the Pot as you will have connected 5v thru the pot to gnd and overloaded the pot. Its been done many times before.
So beware.
Les

[fordgt40]

Les

Now there speaks the voice of experience

David