12V DC-DC regulator - suggestions please!

[down...2 greens]

I'm installing an LED strip in the saloon with a simple PWM motor speed controller as a dimmer - the setup seems to work fine when tested. The strip specifies a 12V supply so I'm wondering if it would be advisable to include a cheap 12v-12v converter to ensure the input doesn't exceed 12V (during battery charging etc)? Or would it be enough just to keep the dimmer a bit less than full bright? The strip is intended mostly as mood/courtesy lighting so I would expect to have it dimmed normally anyway.

If the converter is the way to go could someone link to a suitable example, because I'm baffled by the choice!? I did find some older threads on the subject but the links to eBay etc have all expired...

Thanks in advance

 

[Daverw]

Something like this?
Amazon.co.uk

 

[William_H]

I would suggest the controller should be fine on 15volts. However with 15v in the LEDs will also get 15v at full brightness. So best set for a lower maximum setting perhaps a resistor in series with the brightness controller. Or just discipline to reduce brightness when on charge. ol'will

 

[down...2 greens]

That regulator does look like it would do the trick OK, thanks for the suggestion (although maybe it's overkill given that the 5m strip came in at about 4 quid!)

I could just go with Will's idea and avoid having the brightness turned up full - in that case I suppose it would be wise to include a dedicated fuse rather than just rely on the switch panel protection....

 

[PaulRainbow]

Cheap LED strips often don't last long if subjected to charging voltages. 14+V through something that's meant for 12V isn't a great idea. At best, they get hot. I prefer to fit DC-DC converters. My own boat is 24V, but i fitted it with 12V LEDs and a DC-DC converter. The light work perfectly and you don't get fluctuating brightness due to voltage variations. Better quality LED lights often don't have these issues, as they have electronics built in.

This should be OK : DC-DC Step Down Power Module Voltmeter 4V-38V to 1.25V-36V 5A Buck Converter *UK | eBay

 

[down...2 greens]

Great, thanks Paul - I'll give that a go.

 

[Refueler]

Its well to remember that unlike the old wire wound controllers that varied resistance and therefore voltage out ... PWM are digital and they vary the output by 'pulsing' from low to high ... the high is still at the max voltage that is into the controller ...

Therefore the resulting effect is 'virtual' lower voltage due to the timing of the pulses being longer ...

Here is an online explanation :

Understanding the Basics of Pulse Width Modulation (PWM) - Technical Articles

Therefore the DC-DC converter is a good idea anyway. Hopefully your PWM controller is a reasonable one and will work with the converter ...

 

[Alicatt]

Its well to remember that unlike the old wire wound controllers that varied resistance and therefore voltage out ... PWM are digital and they vary the output by 'pulsing' from low to high ... the high is still at the max voltage that is into the controller ...

Therefore the resulting effect is 'virtual' lower voltage due to the timing of the pulses being longer ...

Here is an online explanation :

Understanding the Basics of Pulse Width Modulation (PWM) - Technical Articles

Therefore the DC-DC converter is a good idea anyway. Hopefully your PWM controller is a reasonable one and will work with the converter ...

And that is why I use a nice old fashioned analogue power supply for my ham radio, no nasty harmonics off of it like you get from some of those PWM PSUs, even the new version of my PSU is PWM and they do have some "noise" from them

 

[andsarkit]

Why not use an LM7812 linear regulator with no noise problems? You can get low drop out (LDO) versions which will still give 12V when the battery is down to 12.5v. It is only a small current and small voltage drop so the heat generated can be lost with a small heatsink or bit of aluminium plate.

 

[William_H]

Its well to remember that unlike the old wire wound controllers that varied resistance and therefore voltage out ... PWM are digital and they vary the output by 'pulsing' from low to high ... the high is still at the max voltage that is into the controller ...

Therefore the resulting effect is 'virtual' lower voltage due to the timing of the pulses being longer ...

Here is an online explanation :

Understanding the Basics of Pulse Width Modulation (PWM) - Technical Articles

Therefore the DC-DC converter is a good idea anyway. Hopefully your PWM controller is a reasonable one and will work with the converter ...

I would disagree in that a PWM voltage converter will feed in to a capacitor which will charge on the go pulse but not right up to the supply voltage meanwhile the voltage sensing coming off this capacitor will sense when output voltage reaches the desired output voltage and throttle back the rate of PWM to stabilise.
This is unlike a PWM motor speed controller which does feed pulses of full voltage to the motor but the inertia of the motor means it can not accelerate as fast as the pulses so operates smoothly. ol'will

 

[William_H]

I would disagree in that a PWM voltage converter will feed in to a capacitor which will charge on the go pulse but not right up to the supply voltage meanwhile the voltage sensing coming off this capacitor will sense when output voltage reaches the desired output voltage and throttle back the rate of PWM to stabilise.
This is unlike a PWM motor speed controller which does feed pulses of full voltage to the motor but the inertia of the motor means it can not accelerate as fast as the pulses so operates smoothly. ol'will

Forgot to mention a buck PWM regulator will have an inductor in series with the output before the capacitor and a flyback diode to recover inductive energy on each pulse. ol'will

 

[down...2 greens]

Quick update: all seems to be working ok with a converter of the type suggested above. For info, the dimmer is indeed a PWM motor speed controller.

Thanks everyone!

 

[st599]

Quick update: all seems to be working ok with a converter of the type suggested above. For info, the dimmer is indeed a PWM motor speed controller.

Thanks everyone!

An additional test you need to do is to check your VHF reception - PWM can put a lot of noise out at random frequency ranges.