Do you have to use a relay or can you just use another transistor or just one transistor? Relays that have to switch fast dont last as long. Better to use a transistor.
Do you have to use a relay or can you just use another transistor or just one transistor? Relays that have to switch fast dont last as long. Better to use a transistor.
I'm sure I posted this question before but when it's "fading", what is the battery voltage ? It may start off at 12v but it could be you have a weak or discharged battery.
I'm sure I posted this question before but when it's "fading", what is the battery voltage ? It may start off at 12v but it could be you have a weak or discharged battery.
I use 12v Wheelchair batteries, and they are staying at 12V.
The input to the interface is a miniature transformer Maplins LT44 side one, 2 wires 1000 ohm side two, 3 wires 100 ohm ?? each side. I didn't exactly know which way round to put it, and guessed from earphone 1 tap to centre tap (100 ohm) then towards the transistor 1000 ohm. I'm just thinking that this might be the wrong way round. I'm not sure which way round matching transformer should be. If this was wrong would it fade my computer output?
I'm wondering if the capacitor is building up a charge as it's used. Maybe try a resistor connected across it to pull the voltage down between keystrokes.
(edit) Actually, re-reading your original post, you say you've substituted C1 with two 1uF caps connected -++- ? Unless you've made a typo, that means one of them is connected in reverse. Not good.
The input to the interface is a miniature transformer Maplins LT44 side one, 2 wires 1000 ohm side two, 3 wires 100 ohm ?? each side. I didn't exactly know which way round to put it, and guessed from earphone 1 tap to centre tap (100 ohm) then towards the transistor 1000 ohm. I'm just thinking that this might be the wrong way round. I'm not sure which way round matching transformer should be. If this was wrong would it fade my computer output?
Actually, re-reading your original post, you say you've substituted C1 with two 1uF caps connected -++- ? Unless you've made a typo, that means one of them is connected in reverse. Not good.
Really though a relay is not needed here a transistor or two would be better. No clicking, no wearout, even if the circuit works as it is getting rid of the relay would be a good idea.
Really though a relay is not needed here a transistor or two would be better. No clicking, no wearout, even if the circuit works as it is getting rid of the relay would be a good idea.
Yes that is an acceptable way to make a non-polarised cap from twp polarised caps. However the circuit does not need a non-polarised cap! Just use a normal 1uF cap with it's - lead to ground.
You are only half wave rectifying the transformer signal, so you are getting all the power transferred as DC. This will be causing issues over time with the sound card output as it is capacitor coupled.
Replace the diode with a 4 diode "bridge rectifier" so that balanced AC is used from the soundcard->transformer->transistor base. Also you need a resistor across the transistor base (base to gnd), try about 470 ohms to 2.2k. That will give a more defined ON/OFF point and give better relay turnoff.
Yes that is an acceptable way to make a non-polarised cap from twp polarised caps. However the circuit does not need a non-polarised cap! Just use a normal 1uF cap with it's - lead to ground.
You are only half wave rectifying the transformer signal, so you are getting all the power transferred as DC. This will be causing issues over time with the sound card output as it is capacitor coupled.
Replace the diode with a 4 diode "bridge rectifier" so that balanced AC is used from the soundcard->transformer->transistor base. Also you need a resistor across the transistor base (base to gnd), try about 470 ohms to 2.2k. That will give a more defined ON/OFF point and give better relay turnoff.
I must admit, I am a bit worried about the soundcard being the bit that's fading.
Your suggestions seem interesting, I will try them, including changing the relay to an output Transistor instead of the relay as suggested by a couple of people. Can someone let me know how to do it, or perhaps use a different transistor that will act as a relay.