Power supply problem

Hi. I am having trouble making a power supply work, and I'm hoping someone can help. I bought several fiber optic lights - they have LEDs in the base that alternately blink 3 colors, and the light goes up numerous fiber optic strands and makes a nice pattern. Each time you push the on/off button, it cycles through a variety of blink programs. Each light runs on 3 AAA batteries (i.e. 4.5 volts DC). The batteries last one night if left on all night and I need to run them for a week, so that is a lot of battery changing. So I decided to try powering them from a deep cycle car battery (12 Volt, 100 Amp hours).

I purchased a regulated power supply that has a 12 V DC input and a 4.5 V DC output with a 2 amp fuse on the input side. I tested the output voltage and it is, indeed, 4.5 volts. I then soldered wires to the points where the batteries connect to the lights and connected them to the output of the power supply. The lights came on - in fact I ran three of the fiber optic lights and combined they drew less than 500 mA. However, when the lights started their blinking program, they went off one by one. I turned the power off and back on, and everything was fine again - no blown fuses, no blown LEDs. However, after a minute or so of blinking, they went off again. This happened whether I had one light or 3 lights connected to the same power supply.

I thought perhaps the blinking was sending interference back to the power supply, so I tried putting a diode in the circuit. That didn't work. I'm still thinking that somehow the blinking is causing a momentary lapse in the power, which is enough to cause the circuit to go off.

Can anyone tell me what the difference is between having batteries and a regulated power supply? Is there anything I can do to this circuit to make it act more like a battery? For example, does it need a capacitor? If so, I'm assuming it needs to be 4.5 volts but I have no idea how many uF it needs or where to put it in the circuit. Or, is it something else?

Thanks for any advice you may have.

hi,
Its sounds as though the regulator inside your power supply is going in to thermal shutdown, from which it recovers when its allowed to cool down.

You could try connecting a large capacitor, say 1000uF at 10Vwkg across the output of the psu.
Ensure that you have the capacitor connected correctly ie: +Vcap to +Vpsu.

Does this help.

It could be related to mains borne hum.
a 4700µF 16 volts cap and a 100 nF despiking cap may help across the 4.5 volts dc.

What is the capacity of your powersupply ?

Thank you, Rodalco and ericgibbs, for the suggestions. I happen to have a 1000uF 10 V capacitor, so I tried it. Unfortunately, it didn't work. Since it is used, I'm not 100% sure it is good. I also had a 1000 uF 35 V capacitor and that didn't work either. They didn't do any damage, but the circuit still went off after the lights started blinking rapidly. Should I try a 4700 uF capacitor and a 100 nF despiking capacitor next? I'll have to buy those, so it may take a few days before I can test that.

Just to be sure I'm hooking this up correctly, the capacitors have negative signs with arrows. I'm assuming the arrows point from the positive to the negative - is that right? Is there a way to test a capacitor to see if it is working?

Rodalco, the power supply is rated for 2 amps. It has a 2 amp rapid blow fuse that hasn't blown. The circuit is only drawing less than 500 mA, so I doubt it is being overtaxed if that is the reason for your question.

Any other parts I should get for future tests as long as I'm going to the store?

Thanks again for the help.

Google has images of things.

Can you give us the model of the power supply?

You mention that these LED/Fiber optic bundles cycle "through a variety of blink programs" when you press the ON/OFF button. This would imply that there is some supporting circuitry that controls this behavior. Is there any indication that this other circuitry is damaged/malfunctioning? It just sounds like a wild card that you haven't considered yet.

Here is a link to the powersupply: https://www.powerstream.com/. Click on DC to DC converters, and then scroll down to PST-DC292, which is a low current DC/DC converter 12 V to 1.5, 3, 4.5, 5, 7.5 or 9 V. If you click on that link and scroll down, there are some specifications.

Thanks.

There is supporting circuitry in the LED lights, but they are working OK. I have about 5 of them, and they all work with batteries but not with the regulated power supply. At first, I thought they might be interfering with each other since I had several connected to the same power supply. But then I tried to hook up just one to the power supply and the same problem happened. If you press the power button on the LED units several times, it cycles through several programs (which are either solid on or blinking at various rates, all one color or alternating among three colors) and then to off (in other words, if you want to turn it off, you have to press the button several times). It seems like this button doesn't work as well when hooked up to the regulated power supply (if I press it, it might or might not move to the next program). If I can get it to a non-blinking program, it stays on. But it always starts on a blinking program when first powered up so that isn't a good solution. I'm pretty sure that there is something different about the quality of the power it is getting from the regulated power supply vs. batteries. Thanks.

Maybe the voltage of the regulated power supply comes up slowly when turned on. Then the supporting circuitry is not automatically reset like when a battery is used and its voltage comes up instantly.

I would definitely try the cap across the 4.5 VDC output as Rodalco suggested. It is usually a good idea to add something like that on the output of a DC/DC converter in custom applications. It looks like the converter you have was designed mostly for equipment that has inherent power regulation/filtering that would take care of this, but your custom application doesn't yet. And since direct battery power is very clean, that may explain why it works with the batteries but not with an un-filtered converter output.