> I don't know why this isn't working. What's the coil current of your relay?
> Maybe the transistor isn't sinking enough current? Try making the resistor
> 1k instead of 10k.
The relay is an omron g5v-1, 150mA. I tried using just about every value for
the bias resistance. I found three levels of resistor values. If the
resistance is too high, it wont switch. If the resistance is what seems to be
the right value, it oscillates. If the resistance is too low the output of
the xc95144 shuts off, possible a protecting circuit? I feared I could have
damaged the part so I tried news pins and new parts, same reaction. My wiring
has been check one million times.
> Yes you can use a MOSFET. Maybe a 2n7000 or something similar. BTW,
> what do you mean by 5v applied to the mosfet from both sides?
My cart has its own power source, a wall wart (500mA) and a 5V regulator.
When I go to dump a cart, I want my cart to power the dumped cart through the
card edge. This has to be a switched connection, because when my cart is
placed in the VCS, both my cart and the VCS would be applying 5V. So If I
used a MOSFET, it would have 5V from 2 sources, one on each end. Is this ok?
I dont want to damage my VCS.
> If it were me, I'd just use a PNP transistor as a switch. Try a 2n3906.
> Connect the emitter to 5V, and put a 1k resistor from the base to your
> XC95144 pin. The collector will be the VCC output. Note that this is
> an inverter, so the control pin should be low to turn on VCC....
I thought of using a PNP but didnt try because the XC95144 is setup to output
5V, but it really only outputs max 3.7V, which wouldnt switch the transistor.
I think the problem lies in the XC95144. I have a 20Mhz clock running the
logic and I think I am getting some funky feedback or RF interference.
I dont really want to try the MOSFET idea until I know I wont harm anything.
Thanks for the help guys,
Vern
>
> I don't know why this isn't working. What's the coil current of your relay?
> Maybe the transistor isn't sinking enough current? Try making the resistor
> 1k instead of 10k. Also double check your relay wiring...there are ways
> to build an oscillator with just a battery and a relay. Yes you can use a
> MOSFET. Maybe a 2n7000 or something similar. BTW, what do you mean by 5v
> applied to the mosfet from both sides?
>
> If it were me, I'd just use a PNP transistor as a switch. Try a 2n3906.
> Connect the emitter to 5V, and put a 1k resistor from the base to your
> XC95144 pin. The collector will be the VCC output. Note that this is
> an inverter, so the control pin should be low to turn on VCC....
>
> Oh wait. Is the XC95144 a 5v part or a 3v part? If it's a 3v part, this
> won't work. The output has to go all the way to 5v to turn off the PNP.
> And it could cause the oscillations in your relay driver if the pullup
> is weaker than expected by the designer of your circuit. So try a smaller
> resistor (1k) if you use that circuit, etc...
>
> Hope this helps!
> -Chris
>
>
> On Mon, 27 Jan 2003 mickey_m@xxxxxxxxx wrote:
>
> > Anyone willing to help with an analog question? I am ok with digital, just
> > not analog.
> >
> > I have a cart I made that allows me to download games to it so I can play on
> > the 2600. I am trying to add a cart reading function to it (you plug a cart
> > into my cart and you can dump it to pc). Which means I need to apply power to
> > the line that normally is the VCS power (I do not use VCS for power). My
> > logic is all handled in a CPLD XC95144 and I would like the power to be
> > applied when it says. Pins on it can only supply 24mA. I tried using a relay
> > with a switching transistor (something like this:
> > http://www.rentron.com/images/rely-drv.gif), but I cant get it to work right,
> > the relay oscillates on and off. I tried manipulating the bias resistor and
> > tweaking it other ways, but no go. So I am guessing that I need to to it
> > another way.
> >
> > Can I use a MOSFET? If I do, is there going to be an issue when my cart is in
> > the VCS, there will be 5V applied to both sides of the MOSFET from separate
> > power sources. Is this a problem?
> >
> > Thanks
> >
> > Vern
> >
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