Alison Lewis wrote: >I would like to flip a switch and have everything >powered. > >I have: > >(1) A MP3 player that runs on 1 AAA Battery (1.5V) RIO >FUSE >(2) Pic Chip with one sensor >(3) Audio Amplifier that uses 4 AAA Batteris with >speakers >(http://www.si-technologies.com/frontEnd/cm_productDetail.jsp?productID=28) > >Want them all to run off power from the wall. Should I >just get three different power adapters one for each >device? (which is impossible for the MP3 player)or can >I make them run off of one power supply? How does one >start to think about what is needed? Are there any >good power tutorials out there? > As everything runs on AAA batteries the total current used by your equipment must be small. I would guess total 300mA (0.3 Amp) at the most. Look for a powersupply that can supply 300mA or more. Your highest voltage is 6 or 7 Volt (4 batteries). Check the manual of the audio-player for the max voltage. Check also the printings on the unit itself. Often it is near the powersocket. For the actual voltage measure the voltage of 4 brandnew batteries to see for yourself. You need a meter (universal meter that can measure Voltage AC and DC, Ohm and mA). Check the voltages before you connect anything to your expensive equipment (voltage AND polarity). If you connect wrong (same idea as putting the batteries wrong way around, all 4 of them) you might have to buy new audio equipment. Buy a 6VDC regulated powersupply . 300 mA or more. Maybe one came with your audio-amp ? Maybe friends have a leftover powersupply (equipment broken, powersupply still working). Your requirements are modest, MANY powersupplies (can) supply more milli-amps than you need. (that is OK) A 7Volt or an 8V or a 9V DC regulated supply can be made to work. If you can find a 9Volt regulated powersupply you can put 3 diodes in series. It will drop 2.1 Volt about and you get 7 Volt. To get 5 Volt make a voltage-regulator for 5 Volt. Connect it to any voltage 6V or higher. Directly to 9V is fine. (Google for 'powersupply' 'regulated' 'DC' '78L05' '7805' 'LM317' 'battery eliminator') Or buy a 78L05 voltage-regulator IC. It looks like a transistor and fits easily in the battery compartment. Wrap the circuit for insulation so it cannot touch any metallic part in the battery-compartment. Before wrapping it in insulation, run the equiment at max current (LEDs ON) and feel if the regulator gets hot. You need another regulator for the single battery MP3 player. You need 1.5 Volt (2 Volt max). This is an unusual voltage. Google for it. You could use an LM317T (or a 100 mA version of the same ). It can supply 1.3 Volt and up. With 2 resistors it will give you 1.5 Volt. The input power for this regulator comes from the 6.0VDC (or higher) regulated powersupply. The LM317 can accept up to 10VDC input easily. So now you have all 3 pieces of equipment running from mains power. Only the 6.0VDC powersupply is plugged into the mains. If the 6.0VDC powersupply has an ON/OFF switch and a POWER-ON indicator you got it made ! The audio-amp is connected to the 6.0VDC powersupply. You have a 5 Volt regulator or a diode for the PIC circuit. Power comes from the 6.0VDC powersupply. You have a LM317 type volt.regulator to get 1.5 Volt.. Power comes from the 6.0VDC powersupply. --- WALWARTS. Walwarts are very common. Look in electronic stores and audio-equipment stores. Wal-warts can be AC or DC. They can be dangerous for battery-powered equipment because walwart voltages usually are higher than stated on the label and box. Sometimes much higher. Beware! 9 Volt (nominal) is a common voltage. And a good choice. Be sure to get one with DC output To get a stable voltage from a walwart, add an LM317T voltage regulator. Output 6.0VDC is set with 2 resistors.. For 6 Volt out, the LM317T needs 8 Volt (or more) in. The LM317T can handle high input voltages, way over 20Volt. But gets hot at higher voltages (needs a heatsink). That gives you the 6V for your audio amp. And the 6.0V for the 5V and 1.5V regulator. See up. Careful !! Before you connect the 3 pieces of equipment you have to verify this: Check if the minus battery-trminal is connected to the chassis. I expect this to be true for all 3. In that case, all's fine, no problems. If you do not find the minus battery-terminal connected to common, please check if the Plus terminal is connected to chassis. If not, all is OK (chassis is floating). If you find Plus-battery-terminal connected to chassis you have a very serious problem. You cannot connect that piece of equipment (it causes short-circuit when you least expect it, first-hand experience). You have to use a SEPARATE powersupply for that piece of equipment. This plus-to-chassis case I have never experienced with commercially-made equipment. I do not expect you will find it with yours. Herman in PHL. -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist