5-volts DC regulator for portable MP3 player on motorbike

This  is USB motorcycle power supply circuit. Motorbike repairman came to my house. Said, you know the story of how I like to build various electronics projects are always. And Talk to exchange knowledge with each other.

During this time, he had been installed the stereo in a motorcycle. Can turn to music Sound of reasonably good.

The regular budget, $ 50, depending on the speaker. (The bass -treble as you like) And small amplifier but high power (around 50 watts)

The source of of music. He chose a portable MP3 player. Since there are several advantages as follows:
– small, easy to install.
– Battery built-in so not require a external power supply. When power is applied to charge it with the home AC power.
– Withstand vibration better
– Music store has hundreds of songs or more.
– To listen to FM radio.

Typically, he allow customers to buy into it. Since there are many to choose price under 20 $.

However, using this a portable MP3 player (as example Figure 1) It is not easy, because the battery runs out of power fast. Listening to music is not long or discontinuous, it must be removed to renew to charged.
Figure 1 The portable MP3 player

He had the idea to adapt draw power from the battery of the motorcycle used as a power supply of this portable MP3 player instead.

Based such a problem, I see that is interesting so Thus volunteered to help him, by Appropriate focus on quality, ease of build. and saving budget (lower than 20$)

Figure out a way to match

He has further commented that the battery provide voltage of 12-volts. But this MP3 player use 5-volts power supply so must to have to the device to reduce voltage to 5-volts fixed. Because too much voltage may damage or permanently destroy the semiconductor chip in this MP3 player.

The current use he not tell me but I think do not many current because it use small LCD display and use one 1.5V battery only.

I think that the good device reduce voltage, is a steady 5V regulated power supply there. In In mind that use IC-7805 pay fixed voltage 5V 1A, Thus try to think of ways to make the design work, as Figure 2 appear to be more effective available.

Figure 2 the 12VDC to 5VDC regulator circuit using IC-7805

The working principle.

We try to understand the circuit better. When connented the battery the current will flow through D1-diode by it serves to protect the connecting wrong polarity,is allow the positive only.

Also, while the 12-volts battery very weak, may be noise mix with voltage battery. But when has D1 will has new rectifier on positive voltage only that can get with them.

Then the current flow to C1. Which serves as filter to smooth. And The C2-capacitors acts reduce high noise frequency.

Then the input of IC1 and supply voltage of 5V regulated at output. By has C3 to filter voltage to smooth and has C4 reduce noise other on level.

Although IC1 would then overcurrent protection. But as a precaution. I insert F1-fuse protect over current of 0.5 A.

And I added ZD1 to protect over voltage., If the voltage exceeds 5.6V. Would be current flow through ZD1 lot. Makes F1 lacking in the end.

For LED1 to show the performance of circuit., If a 5-volts LED1 will light up. Except F1 lack or no power input. The R1-resistors connect to limited current of LED1 perfectly.

How to builds
For the prototype. I assembled two sets him, both on the universal PCB board and on PCB as Figure 3 is Actual-size of Single-sided Copper PCB layout and has components layout as Figure 4 same generally projects.

Figure 3 the Actual-size of Single-sided Copper PCB layout.

Figure 4 the components layout.

Figure 5 The prototype based on this projects.

You should wiring and components for errors. Rub pin devices, to help soldering easier, and leg positioning device correctly. In particular the electrolytic capacitors and diode.

Also, proper soldering with a soldering iron, no larger than 30 watts and use the lead for good.

Until success is a prototype based on Figure 5.


When soldering equipment and review their completed successfully. To take the 12-volts battery to enter in this circuit will see that LED show power on is indicated circuit works so well.

Then, try to take the portable MP3 player to the Motorbike as Figure 6 It turns out that a good result he let the fire is not left open several hours before this circuit that actually works. No problem

The parts you will need.
IC1———-IC-7805 DC voltage regulator
D1———– Diode 1N4007
ZD1——— Zener diode 1N4007
LED1——- LED as you need
C1———– 1000uF 25V Electrolytic
C2, C4—— 0.01uF 100V Mylar capacitors
C3———– 100uF 25V Electrolyte
R1———– 220 ohm 10K 0.25W -5%
Heat-sink 1 pcs.
PCB 1 pcs.


  1. Paul Brace January 10, 2014
  2. pete September 21, 2016

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