telescope control

LCD frequency counter telescope control elektor november 1981 — 11-21 regulator is used as the maximum current consumption for the entire counter is not more than 30 mA. In the first case, power can be provided by an ordinary PP9 dry battery which will give approximately six hours of contin- ual operation. Resistor R9 will not be needecl. If on the other hand the PP9 is to be replaced with a NICAD, R9 will be required since this provides a path for the NICAD charging current when the counter is supplied with an external 8 ... 12 V AC source. The value of R9 is dependant on the NICAD used and must be calculated to provide a charge current of 20. . . 25 mA when the NICAD is discharged. Resistor R8 acts as a limiting resistor to prevent excessive dissipation in the regulator. The final option is an external DC power source and this wilt appear in greater detail in a future article. Construction Having said all there is to say about the relatively simple circuit we can move on to co...