Stepping down power supply

Using Arduino General Electronics
1

Hi,

I currently have a circuit that is powered by a 12V supply that I step down using a 7806. I take 12V to power some solenoids and I also use it to as an input to a 7806 with the 6V going to an Arduino Nano. This works fine but after a while the 7806 gets quite hot (It has a little heat sink on it).

I now want to upgrade to 24V solenoids and so change the 12V in to 24V in. I believe I can use the same 7806 (the specs say it can take up to 30V) but I assume it will get even hotter from 24V. Can I use a double stage step down; 24 to 12, 12 to 6? Is this the best way or is there a better way to go from 24V to 6V.

Thanks in advance.

2

MartynC:
I now want to upgrade to 24V solenoids and so change the 12V in to 24V in. I believe I can use the same 7806 (the specs say it can take up to 30V) but I assume it will get even hotter from 24V. Can I use a double stage step down; 24 to 12, 12 to 6? Is this the best way or is there a better way to go from 24V to 6V.

It will get much hotter, yes. It will be converting 18V into heat instead of 6V.

A switching converter is much better for large voltage changes: 5v dc buck converter for sale | eBay

3

Like fungus said,use a switching regulator. I have this type:

http://www.ebay.com/itm/10pcs-LM2596S-Power-Module-DC-DC-Buck-Converter-Step-Down-Module-DC-5V-3A-LM2596-/251511437338?pt=LH_DefaultDomain_0&hash=item3a8f3ff81a

and until now I had no problems with it.

4

Hi, with your existing circuit do you have bypassing capacitors around the 7806?
If you go to 24V , switch mode supply will be the best.

Tom.... :slight_smile:

5

Thanks,

luisilva,

this is the one you pointed to:

These are the ones I can get locally. Similar but not exactly the same.

  1. US$0.47
    Input: DC 3 V to 40V. Output: DC 1.5V to 35V

  2. US$0.56
    Input DC 3.2V to 40V. Output: 1.25V-37V

The first only has one diode while the second has 2. Does this make a difference?
Does the 50V capacitor on the first one make it better or worse?
The first one does have noise suppression though.

are the modules based on the LM2577-PK also OK?

6

TomGeorge:
Hi, with your existing circuit do you have bypassing capacitors around the 7806?
Tom.... :slight_smile:

yes. I took the circuit from Derek Molloy’s video on Youtube

I use a 7806 and an extra diode on the output though.

7

I actually have several of these regulators. I bought to invert voltage (input +12V and get in the output -9V, for example), but I bought several because I thought that they can be useful to other things (and they are cheap).

About the question of the diodes, I really don't know (I don't have the schematic). The question about the voltage of the capacitors you mus choice a capacitor with a few volts more than your application. If you say that your application will have 24V, then the 35V capacitor is OK, but you can chose too the one with 50V.
If they said in the specs that the input is up to 40V the capacitor may not be 35V only, so, they can be only different in the picture, but in reality be exactly the same.

8

Thanks for the quick reply.

I usually pad my orders to make the postage worth while. US$5 for a 50c item doesn't make sense to me so I will buy a range of different ones and I see what I get.

9

I have now found many step down converters that do not say they are buck converters. Are they the same?

They seem to have the same components / look the same.

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