batteries ->

[Cserny Zsolt]

Welcome,

there is any effect in PI detectors, the changing voltage of the batteries?
(For example IC offset or, especially the delay time, if the coil get not 12,2V but 11,7V)

[Gary]

Re: batteries ->

In my experience, There are some changes on some PI Units as batteries lower in voltage. But not usually frequency or offsets. Most designs are fairly stable in that way. Particularly if they use 555's or some other stable osc device. In my design, "Garys PI Metal Detector", I use a REG1117A Voltage Regulator to stabalize the entire circuit.

But in some detectors, you can get some drift, loss of stability to ground effects and lower sensivity, as the batteries go down.

Take care.....Gary

[Cserny Zsolt]

Re: batteries ->

>But in some detectors, you can get some >drift, loss of stability to ground effects >and lower sensivity, as the batteries go down.

I have similar experiment.
(Sorry, my english is not perfect but i try to explain.)
The PI detector has dual supply. -12 0 +12
The coil is between 0 and -12V this is the high consumed circuit came directly from the battery. The amplifier ICs get +12V stablilized voltage, the monostabile multivibrators get -5V this is stabilized also. When the battery go down, the ICs will not affect for a time, but the coil immidiatly.
I tested my detector with 2 batteries and I used a dual-switch to change the batteries between the high and low consumed circuit, and it seems to me that are minor changes in the shape of the decay curve. Maybe the whole equipment have to separate from the batteries, with stabilizators, I dont know.