12 Volt 5 Amp Power Supply With Mini Light Bar That Draws 6 Amps

[JASII]

Hypothetical question here. With a 12 volt 5 amp power supply, if a mini light bar is plugged in that is rated at 6 amps, what is likely to happen? Will the mini light bar work, but just not be as bright? Will it damage the power supply?

https://www.amazon.com/gp/product/B07K9R65C6/?tag=cpf0b6-20

 

[wtp]

sending a PM

 

[JASII]

12

 

[wtp]

OK the PM was directions to change that
it might be too much for it.
i always think that they over rate power so it sounds bigger than it is.

 

[JASII]

I think it is likely to damage the power supply, unless the supply includes over-current protection.

 

[RFI-EMI-GUY]

Hypothetical question here. With a 12 volt 5 amp power supply, if a mini light bar is plugged in that is rated at 6 amps, what is likely to happen? Will the mini light bar work, but just not be as bright? Will it damage the power supply?

https://www.amazon.com/gp/product/B07K9R65C6/?tag=cpf0b6-20

You are likely to start a fire. It is seldom a good idea to use a lower rated power supply than called for. While it "might work" chances are that it won't under some circumstances.

I bought a 12V 1 amp switching power supply that was rated 85-240 VAC 50/60 Hz. Worked great here in the US all day long for years. Flew to Edinburgh Scotland checked into a hotel, plugged it in and before I even connected a load (radio battery charge base), it exploded. I have no idea why. Was it not really rated for 240 volts 50 Hz? Maybe the mains voltage a bit high?

Look at the warnings the vendor has added: If your light bar is really 6 amps it will not "be great". If your "6 amp" lightbar is incandescent it certainly will draw far more than 5 amps when cold. You will really have a light show!

 

[JASII]

What I am finding is there are two ways to provide over-current protection:

1) Protect the circuit with a fuse or circuit breaker, which opens on overcurrent.

2) A current limiter circuit can be set for the maximum current permissible. Typically a current sensor (low resistance resistor) is in series with the output current, which develops a voltage proportional to the current (Ohm’s Law). A comparator circuit monitors this voltage and compares to a threshold voltage. When the output current rises above the permissible level, the output stage of the power supply folds back, either shutting output off until reset, or limiting the current to the max allowed.

Certainly, a power supply like the one on amazon doesn't have a fuse or circuit breaker. Could it have a current limiter circuit?

(The pessimist in me thinks not.)

 

[kruser]

i always think that they over rate power so it sounds bigger than it is.

Yep, that and the fact that many supplies output current ratings are really for "intermittent" use. These will have a lower "continuous" current rating that is not always listed in a products specs. So a power supply that claims to handle 5 amps may really only handle 4 amps continuously as an example.

 

[JASII]

Yep, that and the fact that many supplies output current ratings are really for "intermittent" use. These will have a lower "continuous" current rating that is not always listed in a products specs. So a power supply that claims to handle 5 amps may really only handle 4 amps continuously as an example.

Great point. I think Astron or other similar power supplies might specify continuous load vs non-continuous load.

 

[RFI-EMI-GUY]

What I am finding is there are two ways to provide over-current protection:

1) Protect the circuit with a fuse or circuit breaker, which opens on overcurrent.

2) A current limiter circuit can be set for the maximum current permissible. Typically a current sensor (low resistance resistor) is in series with the output current, which develops a voltage proportional to the current (Ohm’s Law). A comparator circuit monitors this voltage and compares to a threshold voltage. When the output current rises above the permissible level, the output stage of the power supply folds back, either shutting output off until reset, or limiting the current to the max allowed.

Certainly, a power supply like the one on amazon doesn't have a fuse or circuit breaker. Could it have a current limiter circuit?

(The pessimist in me thinks not.)

Stuff sold on amazon tends to be the cheapest commodity available. Usually a fuse or overtemp device is used and the result is permanent failure of the power supply.

On the other hand I have on my desk a HP E3614A 0-8V 0-6A DC power supply I use for tuning and testing Motorola Saber radios. It is a precision device with adjustable current foldback. If a radio draws too much current, neither the radio or power supply will suffer any damage. It simply shuts down as in your description 2) . This power supply when new was close to 800 US dollars.

 

[a417]

Great point. I think Astron or other similar power supplies might specify continuous load vs non-continuous load.

Most reputable power supplies will give you that informatio on a specification sheet or product description.

 

[K5MPH]

You could over heat the power supply not good idea......................