Help connecting 4 ch remote RX with voice recorder module.

[RobMW]

Hi Collective brains trust.
I am trying to use a 4ch 315MHz remote control module (http://www.suntekstore.co.uk/produc...remote_control_transmitter_and_receiver_.html) to work with a 45 Second Voice recorder module (http://www.siliconchip.com.au/Issue/2007/December/An+Enhanced+45-Second+Voice+Recorder+Module) so that I can playback any of the first 4 recorded sounds.
To playback a chosen sound the voice recorder just has to have a momentary connection from the Message Control "link" M1,M2,M3 or M4 to the GND. After the link is made the sound plays to the end. It all works well with press button switches so I know thats all working.
When I connect any one M1-4 wires to the D0-3 pins on the remote RX unit the sound plays fine. (GND from the voice recorder connected to the GND on the RX ) If I try and connect a second M* everything stops working. I connected a diode between the D pins and the M wires thinking there was some electrical signal being fed back into the RX module but this didnt help.

Im considering forking out for another remote with relays but the beauty of the first module is that is so small, about the size of a matchbox.

Any help greatly appreciated.

There is a info sheet download at the bottom of the suntekstore page but it doesn't help much.
http://iw.suntekstore.com/attach.php?id=10011352&img=RF208PC.doc

 

[Harald Kapp]

Welcome to our forum.

I think the description of the receiver is misleading. I can't see any relays. DO0...DO3 are most probably only logic level outputs.
The remote operates from 5V, what is the internal operating voltage of the voice recorder (not the externally applied 9V-14V)? If it is not 5V, then there is a possibility of stray currents upsetting the circuits when connected.

You could use 4 photocouplers, driving the LEDs from the receiver board and using the transistors as switches to select the voice channel. This wil completely decouple receiver and voice module (no need for a common ground).

 

[RobMW]

Thanks Harald. I'll give that a go. Now to learn how to wire them up.
I found some on the local component website (JayCar) but they have six pins.
I think it will be something like the attached. I just have to work out the pins and value of any resistor.

 

[Harald Kapp]

Looks o.k.
The resistor is calculated as any LED seres resistor. If in doubt, see the LED tutorial in our tutorial section.

 

[RobMW]

Unfortunately the optocouplers didn't work. As soon as I connect the second optocoupler to the common GND of the RX it stops working. So its not the voice recorder causing the problem. Ill keep experimenting with that.
I have asked the supplier of the remote for any schematic diagrams they may have to support their claim that it can be used to control TV's, lights, fans ....etc
Im thinking for it to do that it needs to be hooked up to some beefy relays.

 

[Harald Kapp]

Could you sketch the setup with two optocouplers? I'm wondering what may go wrong since the vouce rec works with switches.

 

[RobMW]

Will do. BTW I didn't bother connecting up the voice recorder. I just connected an old style needle deflection multimeter to the optocoupler outputs. Ill try and do some more testing tonight. In a couple of hours here in Oz.

 

[RobMW]

I did some further investigating and discovered that the D0-D3 are not latching but are passing 5V !
I rewired the optocouplers as per my first schematic and ta da!. It Works (using a multi meter anyway)
So it was "Carbon Based" error ie human... me. Not following my original diagram. I was thinking the optocouplers needed power from the 5V battery and a connection to the RX would close the circuit but it was in fact shorting. I should have paid attention to my first schematic.
Thanks for your help Harald. I would never had known about the optocouplers otherwise.

 

[Harald Kapp]

Good it works.