24VDC to 12VDC using LM317T questions

[ericgibbs]

Hi Sarma.

in the case of series resistor, the input voltage available for LM317 will change as per the load current.
Yes it will vary as the load current changes, but will not be a problem as long as the current drawn is <=0.6Amp

In view of power economy, i feel the switch based solutions are efficient and perhaps may not be so costly. with an additional 5 or 6 components the job is done.
With regard to efficiency I agree!

Datasheet of MC34063 attached.pehaps there are cheaper Switches available off late.

as the power requirement is more than the capacity of this IC , an additional pass transistor may be required.

As its a 'one off' project I would still use the cheapest option, resistor.

In the past I have reduced 'excess' voltages by removing a few turns off the transformer secondary,
thats a 'zero' component cost way of doing it

 

[mvs sarma]

Lovely Eric--the Zero component way..

 

[qsiguy]

Loving all the feedback and discussion. This project is experimental but may not be a one off. If I can get it to work efficiently and reliably for a low cost we may integrate this circuit into quite a few of our panels. A majority of our panels utilize 24VDC and these lights are all 12VDC. Some of the simple panels that can run entirely on 12V it's not needed or larger panels where there is ample space we just add a 12V power supply to run them but where space is tight or cost if a factor, adding a 2nd power supply just for the neon light isn't an option.

Would that 10W resistor need a heat sink of any kind?

 

[ericgibbs]

Loving all the feedback and discussion. This project is experimental but may not be a one off. If I can get it to work efficiently and reliably for a low cost we may integrate this circuit into quite a few of our panels. A majority of our panels utilize 24VDC and these lights are all 12VDC. Some of the simple panels that can run entirely on 12V it's not needed or larger panels where there is ample space we just add a 12V power supply to run them but where space is tight or cost if a factor, adding a 2nd power supply just for the neon light isn't an option.

Would that 10W resistor need a heat sink of any kind?

hi,
The resistor should be mounted so that it get rid of the heat, not tight down onto a pcb, standing clear and away from heat sensitive components.

Some types have a 'brass' type body, that are designed to bolt to the metal enclosure