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vinrads 29th Apr 2019 8:09 am

1.5Volt supply
I have a Panasonic cassette player used to play my talking books , this uses just one 1.5volt battery , I was thinking could I utilise the 5 volt from the USB socket on the JVC DAB radio/CD player as I play the cassette through this via the jack socket, I supose the question is how to drop the 5volt to 1.5volt?


FIXITNOW 29th Apr 2019 8:47 am

Re: 1.5Volt supply
LM317. Can get a kit from ebay cheap I use them for battery valve portables to do the heater current.

lesmw0sec 29th Apr 2019 8:48 am

Re: 1.5Volt supply
Assuming that the current draw is within reason, I would have thought an LM317 would do, as it can be adjusted down to 1.2V. Not sure what the minimum input votage is for it though.

pip5678 29th Apr 2019 10:38 am

Re: 1.5Volt supply
I have one of those modules from an eBay merchant in China. I've just tested it and will give 1.5V off a 5V supply, claimed current rating is 1.5A but I tested it with no load on a meter.

Herald1360 29th Apr 2019 11:10 am

Re: 1.5Volt supply
Presumably the current draw issue is as relevant to the USB source capability as the LM317? Without a heatsink, a TO220 317 should be OK for about 300mA for 5V in and 1.5V out.

Edit: Looking at the likely module, it should be OK for about an amp with the 3.5V I/O differential. I would think for 1.5A it would need the I/O differential kept very close to the 317 dropout value!

mitajohn 29th Apr 2019 11:34 am

Re: 1.5Volt supply
May be this is interesting:


Input Voltage :

AC 230V-50Hz 14W

Output Voltage :

DC 1.5/3/4.5/6.0/7.5/9.0/12. OV, 6.0VA(Max)

pip5678 29th Apr 2019 11:40 am

Re: 1.5Volt supply
The 99p eBay module I have does have a heatsink. Agreed if anything like 1.5A was being drawn the available current from the USB socket would need to be borne in mind!

vinrads 29th Apr 2019 6:32 pm

Re: 1.5Volt supply
Just checked the lm317t min input is 4.2 v so this should be ok with 5 volts in to 1.5 volts out . The cassette player probably uses a DC to DC converter ,the battery lasts a good while ,I think I could just about squeeze the LM317 and other bits in the battery compartment . Thank's for all the suggestions . Mick.

emeritus 29th Apr 2019 9:46 pm

Re: 1.5Volt supply
Have you tried measuring the current drawn by the player in its various operation modes? The Philips EL3302 draws a pretty constant current of circa 100mA in play, record, fast forward and fast rewind modes, so a simple wire-wound series resistor of suitable wattage rating to drop the excess voltage was all that was needed to use it from a 12V car battery. They did sell a car kit consisting of a resistor in a ventilated metal box with some leads and a plug for which AFAIR they charged about a fiver in 1969: I made up my own.

vinrads 30th Apr 2019 7:56 am

Re: 1.5Volt supply
I did consider that option ,but I would like to fit it inside the battery case hopefully the reg won't get hot maybe a bit warm warm , I think some experimenting is needed ,Mick.

snowman_al 30th Apr 2019 8:21 am

Re: 1.5Volt supply
Or maybe look at the tiny adjustable DC-DC (buck) converters?
(''Mini DC-DC step down converter volt regulator'' has 4.75 to 23 volts in, 1.0 to 17 volts out, @ 3A, for example. Less than 2.)

Herald1360 30th Apr 2019 8:25 am

Re: 1.5Volt supply
Wheeeeeeee! ???

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