Basic Inverter Components list:

Notes:

1. Q1 and Q2, as well as T1, determine how much wattage the inverter can supply. With Q1,Q2=2N3055 and T1= 15 A, the inverter can supply about 300 watts. Larger transformers and more powerful transistors can be substituted for T1, Q1 and Q2 for more power.

2. The easiest and least expensive way to get a large T1 is to re-wind an old microwave transformer. These transformers are rated at about 1KW and are perfect. Go to a local TV repair shop and dig through the dumpster until you get the largest microwave you can find. The bigger the microwave the bigger transformer. Remove the transformer, being careful not to touch the large high voltage capacitor that might still be charged. If you want, you can test the transformer, but they are usually still good. Now, remove the old 2000 V secondary, being careful not to damage the primary. Leave the primary in tact. Now, wind on 12 turns of wire, twist a loop (center tap), and wind on 12 more turns. The guage of the wire will depend on how much current you plan to have the transformer supply. Enamel covered magnet wire works great for this. Now secure the windings with tape. Thats all there is to it. Remember to use high current transistors for Q1 and Q2. The 2N3055’s in the parts list can only handle 15 amps each.

3. Remember, when operating at high wattages, this circuit draws huge amounts of current. Don’t let your battery go dead :-).

4. Since this basic inverter project produces 120 VAC, you must include a fuse and build the project in a case.

5. You must use tantalum capacitors for C1 and C2. Regular electrolytics will overheat and explode. And yes, 68uF is the correct value. There are no substitutions.

6. This circuit can be tricky to get going. Differences in transformers, transistors, parts substitutions or anything else not on this page may cause it to not function.

The above diagram is a basic Uninterupted Power Supply (UPS) circuit. This basic UPS circuit is a very simple and inexpensive.

This circuit can be adapted/modified for other regulated and unregulated voltages by using different regulators and batteries. For a 15 Volt regulated supply, you may apply two 12V batteries connected in series (it will become 24V) including a 7815 regulator (will be 15V stabilized voltage output). There is a lot of flexibility in this circuit.

TR1 has a primary matched to the local electrical supply which is 240V in the UK (it might be various for other countries, 110/120V or 220/240V). The secondary winding should be rated at least 12 Volts at 2 Amperes, but can be higher, for example 15 Volts. FS1 is a slow blow type and protects against short circuits on the output, or indeed a faulty cell in a rechargeable battery. LED 1 will light ONLY when the electricity supply is present, with a power failure the LED will go out and output voltage is supplied by the battery.

The capacity to keep up the regulated supply with no electrical supply relies on the load taken from the UPS and also the Ampere hour capacity of the battery. In the event that you were utilizing a 7A/h 12V battery and load from the 5V regulator was 0.5 Amp (and no load from the unregulated supply) then the regulated supply would be maintained for around 14 hours. Greater A/h capacity batterieswould give a more drawn out standby time, and the other way around.

The complete explanation about this basic UPS circuit, please go to this page.