for the current i think it'll need high enough for running the vibrator. is it use a Ampere CLam meter to check the A when the vibrator is running?
this is my modification on this circuit.
i add in a 10k ohm VR and replace the R1, R3 into 320 ohm and R2, R4 into 460 ohm.
wat i get is (input voltage is 28VAC, which outpur from my transformer for doing experiment)
when 2, 5 near to 1, 4, (0%), the voltage is 1.18VAC.
50% = 2.00 VAC
75% = 2.23 VAC
100% = 13.63 VAC
(the R1 and R3 will hot when VR set to 100%), who know the reason?
who know the calculation the suitable R1, R2, R3 and, R4 when 10k VR is used and the input voltage is 20VAC.
p.s.: im no so familiar to the LM317..