Help please. Dip switches and mach 3 settings

[john swift]

great to see you have it working even if your not 100% sure which connection you re-made during your investigation

your connection to the VFD looks correct

in practice using the 12V supply probably will work

while the LM317's data sheet gives the minimum supply voltage as V out +3V this will be the worse case accounting for the production spread in the IC's parameters

even if the supply is too low for the regulator to regulate the output as intended

the fact you have a regulated 12V supply
the voltage is likely to be near to 10V and not change too much and
cause the calibration of analogue control voltage to the VFD to vary

John

[Radu_Andrei]

I have another identical supply, so wiring it in series might give me 24v, or 20 due to what you said. I might have a spare laptop charger somewhere, which is 17 or 19v.
If it is a requirement, I.ll do it.
Thanks again for the detailed answer. :)

[cropwell]

I have another identical supply, so wiring it in series might give me 24v, or 20 due to what you said. I might have a spare laptop charger somewhere, which is 17 or 19v.
If it is a requirement, I.ll do it.
Thanks again for the detailed answer. :)

Leave it alone at 12v - if it ain't broke, don't fix it. If you get 0 - 10v on the analogue output, you'll be fine.

[Radu_Andrei]

Ok. Thank you. And yes, the 5v usb cable is run from the pc. I have a phone charger available as well. It reads 4.74v at pc5v and pcgnd.
Does it matter?

[john swift]

phone chargers are not regulated very well
so you will be better off either using the PC's USB port or using a regulated 5V power supply to power the 5V side of the breakout board

John

[cropwell]

phone chargers are not regulated very well
so you will be better off either using the PC's USB port or using a regulated 5V power supply to power the 5V side of the breakout board

John

I use exactly that BoB with a 12/5v dual power supply from a defunct external hard drive. It works fine !