Re: 12v - 5v USB Power Socket
I've had a look into what might constitute a safe 5v power supply for sensitive electronic devices such as iPods & gaming devices that are connected to an automotive system.
Found a few ideas for standard 5v power supplies, but not much really covering the ellimination of electronic noise.
Bear in mind that I have not had a chance to test the circuit, as we do not have breadboarding facilities within the electrical department out here on the rig. So anyone wanting to use this, still needs to verify that the figures listed for the capacitors and inductor are suitible for removing and filtering any transients in the system, and adjust as necessary.
Basically, as we already know, the prados electrical system is 12v, charged by an AC generator (the alternator) and rectified to DC for charging the battery and maintaining voltage throughout the car. However, the filtering on this is crude. Any sensitive electrical system connected directly to the car must perform is own additional filtering to eliminate potential spikes of up to 60vdc, during startup, charging and running. An easy way to eliminate these spikes is to use electronic filters, my circuit uses a capacitor-input filter which is described as a 'Low-pass Pi Filter'.
(Image not entirely clear - can provide a full size PDF version of this if someone wants it)
How the circuit works:
The 7805 voltage regulator should do most of the work so long as at a minimum capacitors C2, C3, C4 & C5 are included.
ZD1 - this zener diode will prevent the output voltage from ever exceeding 5.6v, optional.
R3 & D2 - Power indication LED, optional.
D1 - to disipate any reverse polarity that may occur and damage the regulator, very unlikely - optional.
C1, C2 & L1 - the Low-pass Pi Filter, if not using the filter, C2 should remain in circuit as a decoupling capacitor.
F1 & L1 - marked as 5A rated components, no reason why they can't be 1A rated (smaller & cheaper).
Capacitor values may need to be experimented with, but this system should work ok.
I've included below, some industrial style USB sockets which would be more durable that what can normally be aquired from an electronics store, we have variations of these in our Cyberbase chairs.
Cheers
Matt
I've had a look into what might constitute a safe 5v power supply for sensitive electronic devices such as iPods & gaming devices that are connected to an automotive system.
Found a few ideas for standard 5v power supplies, but not much really covering the ellimination of electronic noise.
Bear in mind that I have not had a chance to test the circuit, as we do not have breadboarding facilities within the electrical department out here on the rig. So anyone wanting to use this, still needs to verify that the figures listed for the capacitors and inductor are suitible for removing and filtering any transients in the system, and adjust as necessary.
Basically, as we already know, the prados electrical system is 12v, charged by an AC generator (the alternator) and rectified to DC for charging the battery and maintaining voltage throughout the car. However, the filtering on this is crude. Any sensitive electrical system connected directly to the car must perform is own additional filtering to eliminate potential spikes of up to 60vdc, during startup, charging and running. An easy way to eliminate these spikes is to use electronic filters, my circuit uses a capacitor-input filter which is described as a 'Low-pass Pi Filter'.
(Image not entirely clear - can provide a full size PDF version of this if someone wants it)
How the circuit works:
The 7805 voltage regulator should do most of the work so long as at a minimum capacitors C2, C3, C4 & C5 are included.
ZD1 - this zener diode will prevent the output voltage from ever exceeding 5.6v, optional.
R3 & D2 - Power indication LED, optional.
D1 - to disipate any reverse polarity that may occur and damage the regulator, very unlikely - optional.
C1, C2 & L1 - the Low-pass Pi Filter, if not using the filter, C2 should remain in circuit as a decoupling capacitor.
F1 & L1 - marked as 5A rated components, no reason why they can't be 1A rated (smaller & cheaper).
Capacitor values may need to be experimented with, but this system should work ok.
I've included below, some industrial style USB sockets which would be more durable that what can normally be aquired from an electronics store, we have variations of these in our Cyberbase chairs.
Cheers
Matt
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