Remote input switching with relays : Will this work
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Doh

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Hello,
First off, I have to explain that I know practically nothing about electronics. What appears is a rough schematic of what I would like to do to use remote controlled input switching in my slowly progressing KG Dynanamic Preamp/Headphone amp.

What appears is sorta hacked together from what I can glean from schematics found elsewhere, but it is my best attempt at coming up with a circuit that half way makes sense. Design goals as following:

1) Implement a practical way to switch inputs in my preamp using a remote control.

2) Use up some parts that I have left over such as the 2SC1815 NPN's from the KG amp.

Some specifications:

1) The relays I plan to use are NAIS DS2Y seriesDPDT relays. 5V, coil resistance of 125 ohms, Nom Operating current 40mA

2) Values for R1 and R2 are not determined. I don't think they need to be very high if they need to exist at all.

Questions:

1) Will this thing even work?

2) Do I have things like the diode pointed the right way?

3) Is this an OK use for the 2SC1815 transistor?

4) What the heck should I make the values of R1 and R2?

I would appreciate any and all help I could get with this. Thanks!

-Doh
 
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aos

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The diode around the relay should be turned around. Its purpose is to protect the transistor from spikes of reverse polarity current that occur when relay is turned on/off (since it's a big inductor).

Otherwise it should work, though the resistor values are where the trick really is. They need to set the transistor's current to whatever is needed by the relay, and so that the voltage drop from base to emitter is correct (all this can be read from various graphs of current versus voltage in the datasheet for particular transistor). If you tell me what that current is for your relay, I could look it up in 2SC1815 datasheet. Possibly another resistor in series with base of the transistor could be added.
 
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Doh

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Thanks for the reply!

The data regarding the relays is as follows:
Pick-up voltage: 3.5 VDC
Drop-out voltage: 0.5 VDC
Nominal Operating current: 40mA +/- 10%
Coil resistance: 125 ohms
Nominal Operating Power: 200mW
Max Allowable Voltage: 10 VDC

The datasheet can be found at:
http://ctlgserv.mew.co.jp/acg/e_nais...e_pdf/ds2y.pdf

I've attached a schematic where I've flipped the diode around and added another resistor before the base of the transistor.
Please let me know what you turn up with the datasheet. Unfortunately, the datasheet is all greek to me. Thanks again for your help!

-Doh
 
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