dc -dc convertor help.

[jorjo]

hi every body.
I'm working around a circuit , but now I have a problem.
In my circuit outlet there are below constants:

5VDC ,5mA

I can't use these parameters foy any purpose becouse they are too low.
I need a DC/DC convertor and current buffer to drive 24VDC & 250mA relay.

I have 24 VDC in another positon and can use it.

pls suggest an IC or circuit.

thanks.

 

[Hero999]

You can't convert 5VDC @5mA to 24VDC@250mA because there isn't enough power.

**broken link removed**

Change the following:

R1 = 680R
T1 = BC337

 

[jorjo]

what about 24VDC @100mA?

 

[ronsimpson]

?????You need 24V at 100mA and you don't have any power?????
A DC/DC converter will not fix this problem.

 

[Hero999]

what about 24VDC @100mA?

Change the 12V in the circuit to 24VDC.

As mentioned above, you need a 24VDC supply, which you said you already have in your first post.

 

[jorjo]

I have 24 VDC from another position in circuit.so I can have enough power .
Isn't it?

 

[jorjo]

also unlimited current.

 

[Hero999]

Please post a schematic.

You don't need to limit the current, the relay will only draw as much power as it needs.

If your power supply is only rated to supply 100mA and the relay requires 250mA, then you're out of luck. You either need to get a power supply which can provide 250mA or get a relay which uses less power.

 

[jorjo]

I draw your recommended circuit in proteus.

but it didn't work properly.
where is output?
answer: collector, I think.

when input is hi or low collector didn't change,becouse you used inductor in collector.

 

[rmn_tech]

The 'inductor' in the Circuit is your relay coil.

Read the current through it in proteus.

 

[jorjo]

he.he.
yes.it is.!!!!!

It isn't my desired solution, becauce i want to use relay out of my designed circuit. my circuit have 3 wires:
IN ,GND,OUT
but i think transistors are good idea.
pls another way .

 

[Electronworks]

Hero's circuit is the best way to do this. Hero's circuit does not have any relay contacts though which could be where you are getting confused. What Hero's circuit is doing is energising a coil (the inductor) that then closes the relay contacts. These contacts are a completely isolated set of contacts and can be though of as just a normal switch that close when the relay coil is energised (when the transistor is ON) and open when the relay is de-energised.

Does this help clarify things?

 

[Hero999]

Here's the circuit with all the modifications.

 

[blueroomelectronics]

also unlimited current.

Where do you get unlimited current?

 

[Hero999]

I missed that, of course you can't have an unlimited current.

 

[tcmtech]

He probably means he has far more power available on the 24 volt circuit than what is likely to be needed.
Mains source Vs a 9 volt battery type situation.

 

[mneary]

He probably means he has far more power available on the 24 volt circuit than what is likely to be needed.
Mains source Vs a 9 volt battery type situation.

More like simulator vs reality.

 

[Vizier87]

Probably he meant max current that can be drawn.

 

[jorjo]

Dear hero999

I need this out also for another purposes.
one of my goals is relay.

 

[jorjo]

i draw a circuit to show my will.
how can I attach a picture file from my PC?