Re: AC to DC ?
Dear chmr,
You can use a simple AC-DC conversion circuit.
http://www.kpsec.freeuk.com/powersup.htm
You need the following:
1. A power transformer to step down 240Vac. You can easily purchase a transformer that can step down to as low as 12Vac. Most power transformers operate at 1A and higher.
2. A bridge rectifier to rectify a 12Vac to approximately 9Vrms.
3. An electrolytic capacitor (2000µF, 50Vdc) as reservoir and smoothing capacitor
4. An electrolytic capacitor (330µF, 25Vdc) as reservoir and smoothing capacitor
5. A Linear Voltage Regulator (LM294 or 7805) with 1A output current rating.
This simple chained AC-DC conversion gives 5Vdc and 1A. Since you need 4.5Vdc, there are a number of possible ways:
1. A simple voltage divider, such that the resistive ratio gives you 4.5Vdc
2. A simple zener voltage regulator at 4.5Vdc
3. You can modified (1) to an Linear Voltage Regulator by means of a Comparator using an Op-amp referenced to 4.5Vdc.
NB: Connect some 100nF or 0.1µF Ceramic capacitors as de-coupling capacitors in parallel to the Output Voltage and Ground, either close to the Voltage Regulator or the ICs.