Your code is correct but the Time Interval is incorrect. AlarmManager accepts value in miliseconds. So for 15 minutes, you need to calculate like below,
15 * 60 * 1000
Try this code,
public void onReceive(Context context, Intent intent)
{
PowerManager pm = (PowerManager) context.getSystemService(Context.POWER_SERVICE);
PowerManager.WakeLock wl = pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, "");
wl.acquire();
Intent App = new Intent(context, LoginActivity.class);
App.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
context.startActivity(App);
Toast.makeText(context, "instantmeter waking restart", Toast.LENGTH_LONG).show(); // For example
wl.release();
}
public void SetAlarm(Context context)
{
AlarmManager am=(AlarmManager)context.getSystemService(Context.ALARM_SERVICE);
Intent i = new Intent(context, PollReceiver.class);
PendingIntent pi = PendingIntent.getBroadcast(context, 0, i, PendingIntent.FLAG_UPDATE_CURRENT);
am.setRepeating(AlarmManager.RTC_WAKEUP, System.currentTimeMillis(), 15 * 1000 * 60 , pi); // Millisec * Second * Minute
}