How to make MCCdec switch an external 4,8v circuit [1 Attachment]

Original sent date : Sat Sep 05 00:17:50 CEST 2009
Hi Leon
 
Thanks for your answer.
 
I've got a technical drawing of the circuit, see attachement.
 
I personaly think that the idea with a mosfet is the best, or do you have another idea?
 
Thanks for thinking with me!
 
Greetings,
 
Gerard van Rekum
 

--- On Fri, 9/4/09, Leon van Perlo <leon@vanperlo.net> wrote:

From: Leon van Perlo <leon@vanperlo.net>
Subject: Re: dinamousers How to make MCCdec switch an external 4,8v circuit
To: dinamousers@yahoogroups.com
Date: Friday, September 4, 2009, 9:35 PM

Hi Gerard,

Good question.

I would not use an opto. Opto's require quite some current to be
activated, which seems waste of energy to me.

Assuming you are working with MCCdec02: Note that MCCdec02 has an
internal operation voltage of (around) 4,15V. It depends on your actual
external circuit, but I think it should not be too difficult to switch
external logic operating at 4,8V with a logic signal of 0V/4.1V. A
simple CMOS logic gate should switch high/low on approx 2,4V given your
supply voltage of 4,8V.

Another option: I don't know how much current your external circuit uses
and wether 4,8V is the minimum required voltage.
An MCCdec02 output can drive approximately 20mA, so if you have a
circuit that makes sound when you simply put 4V on it and it does not
draw more than 20mA, you could drive it directly by the MCCdec.

If your circuit requires more than 20mA and less than 50mA and functions
at 4V, you could also feed it from the Vcc pin on the MCCdec02 and
(de)/activate it by one of the normal outputs. This pin is the internal
power supply for the MCCdec and supplies 4,15V. Note however that the
4,15V is also present during sleep mode, so your circuit must be very
economical in power consumption when not operated. Since the MCCdec02
has a step-up converter on-board, drawing I mA from Vcc draws approx.
5/vbat*I mA from the battery. So on 2,4V battery, 1mA on Vcc will draw
approx 2mA from the battery.

If you need more than 50mA and your horn blows when you simply put 4,8V
on your circuit, switch a logic-level MOSFET (BSS123, BSH103) by one of
the MCCdec outputs (you can connect the gate directly to the output and
the source to gnd/0V. The drain then switches on/off to gnd/0V, so
connect your horn between 4,8V and the drain of the MOSFET. Don't know
exactly by heart, but I think the BSH103 can switch 800mA

Hope this helps,
Leon
> Hallo,
>
>
> Ik wil in een vrachtwagen een extern printje aansturen.
>
> Dit printje gebruikt 4,8v. Nu is dat geen probleem; "gewoon" 4xAAA
> batterijen.
>
> Ik zit alleen met het probleem hoe ik deze module activeer. Het
> printje wordt nu geactiveerd met een drukschakelaar, maar het zou
> natuurlijk mooi zijn dit met de decoder te doen.
>
> Het kan denk ik niet zomaar aangezien we hier met een (externe) 4,8v
> werken.
>
> Hoe kan ik dit het beste aansluiten/ sturen? Misschien iets met een
> optocoupler? Welk type?
>
> Alvast dank voor het meedenken!
>
> Groeten,
>
> Gerard van Rekum
>

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