5.0V 250mA Linear Voltage Regulator - L4931-5.0 TO-92 (ADA2236)

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I am trying to find a power supply for a Nixie Tube/Valve Clock. I need to convert 240v ac down to 5v dc with a maximum 250ma output, preferably with a mini USB plug. Have searched every where I could think of but have not found anything 250ma or below. Could anyone assist me. Cheers GIBBO

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You would be better off with a small 240VAC to 5VDC plug pack or as the Americans call them Wall Warts. They are quite common and most come with 1 or 2 USB A outlets. Just plug in a USB A to what ever you need cable and off you go. I don’t know if Core stock such a thing but they are probably available at Woolworths or the local chemist. Something like your Phone charger. One of these would do if you have a spare one laying around.
Cheers Bob
EDIT: The 250mA is the Maximum current a supply can provide. I doesn’t matter if your power source can supply more. Phone chargers can supply typically 2A. This does not matter. If your clock only requires 250mA that is all it will use. The clock or power supply will not be damaged.

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You might have some luck with sticking a USB connector on an old phone charger. You won’t find anything off the shelf as the USB specifications require at least 500mA be available.

That said, it probably won’t help you much as it sounds like you need current limiting? If a supply limits current on a low impedance load, the voltage MUST decrease proportionally, and if the supply isn’t designed for constant current mode, you’ll just overload the supply.

So do you have some more details about the components you’re trying to power? Because what you’re asking for is physically improbable.

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Hi Oliver
Pretty unlikely something like Nixi clock would require a constant current supply I think.
Cheers Bob

Thanks for your quick reply. I built a Nixie Valve Clock many years ago when I completed Industrial Electronics. Things were a lot bigger and easier then. I just received a new one from overseas knowing I would not have a problem getting the 5vdc supply, but on reading the specs it stated a maximum input of 250ma. I am aware that most USB supplies are 1 or 2 amp and thought that delivering that amount to a 250ma unit may cause a problem. Thanks for clarifying.

Regards GIBBO

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It’s likely that the description means that the device will draw a maximum of 250mA, and the supply must be able to provide at least that. So anything that can supply 250mA or more would work with the device. Do you have a reference for the specifications?

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Thanks for the quick reply Oliver33

I also received the below message from Robert93820 and my reply to him below.







Robert93820
11 September

You would be better off with a small 240VAC to 5VDC plug pack or as the Americans call them Wall Warts. They are quite common and most come with 1 or 2 USB A outlets. Just plug in a USB A to what ever you need cable and off you go. I don’t know if Core stock such a thing but they are probably available at Woolworths or the local chemist. Something like your Phone charger. One of these would do if you have a spare one laying around.
Cheers Bob
EDIT: The 250mA is the Maximum current a supply can provide. I doesn’t matter if your power source can supply more. Phone chargers can supply typically 2A. This does not matter. If your clock only requires 250mA that is all it will use. The clock or power supply will not be damaged.

Thanks for your quick reply. I built a Nixie Valve Clock many years ago when I completed Industrial Electronics. Things were a lot bigger and easier then. I just received a new one from overseas knowing I would not have a problem getting the 5vdc supply, but on reading the specs it stated a maximum input of 250ma. I am aware that most USB supplies are 1 or 2 amp and thought that delivering that amount to a 250ma unit may cause a problem. Thanks for clarifying.

Regards GIBBO

Thanks for the reply Jeff105671.

I received a similar reply below from Robert93820. I think you are right on the ball. Badly worded instructions I think. I believe it should have read: “Requires 250ma”.

Regards GIBBO

You would be better off with a small 240VAC to 5VDC plug pack or as the Americans call them Wall Warts. They are quite common and most come with 1 or 2 USB A outlets. Just plug in a USB A to what ever you need cable and off you go. I don’t know if Core stock such a thing but they are probably available at Woolworths or the local chemist. Something like your Phone charger. One of these would do if you have a spare one laying around.
Cheers Bob
EDIT: The 250mA is the Maximum current a supply can provide. I doesn’t matter if your power source can supply more. Phone chargers can supply typically 2A. This does not matter. If your clock only requires 250mA that is all it will use. The clock or power supply will not be damaged.

Thanks for your quick reply Bob. I built a Nixie Valve Clock many years ago when I completed Industrial Electronics. Things were a lot bigger and easier then. I just received a new one from overseas knowing I would not have a problem getting the 5vdc supply, but on reading the specs it stated a maximum input of 250ma. I am aware that most USB supplies are 1 or 2 amp and thought that delivering that amount to a 250ma unit may cause a problem. Thanks for clarifying.

Regards GIBBO

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