Now that I have been lazy about working on my pinball machine for a while, I got mad enough to motivate myself to work on it. The solenoid driver board is being re-hashed, again but in the meantime I am trying to put together a 6-channel audio mixer and stereo amp.
Just quickly, to update on the solenoid driver board I've been working on the schematics for it. I am at least doing a better job of documenting my work. I will be posting the schematics and my first board layout soon. Due to the board sized limitation on EagleCad freeware, I can only fit (at least I think I can) the circuitry to drive six solenoids. I am fine by this. It makes my solenoid power distribution more modular. I will likely use three boards for 18 solenoids. The EagleCad freeware is limited to a board size of 8 x 10 cm. I could have used KiCad as it is unlimited but from what I have heard it is not as user friendly and everyone has EagleCad which makes sharing much easier. I think I will try KiCad out in the future when the limitations of EagleCad frustrate me enough but the biggest problem I found with it was finding complete libraries for components. Maybe I'm missing something, I do not know. In any case, more posts coming.
Now for the audio mixer and amplifier. I found this circuit diagram and I am planning on using the bottom right one. Instead of the two mono channels, I will change them to a third stereo input.
I will be using the following components for this circuit:
MC33202 - Low Voltage Rail to Rail Operational Amplifier
PDB182-K425K-103A - 10 KOhm Rotary Pot (Log/Audio Taper)
P160KNP-0EC15A25K - 25 KOhm Rotary Pot (Log/Audio Taper)
SPC21349 - Audio Jack
This is the amp that I will be using. The circuit diagram is provided in the datasheet:
TDA7269A - 14W Audio Stereo Amplifier
My speakers:
4899 - Viston Speaker 8 Ohms 30W RMS
I think I may have made a mistake on the speakers or perhaps picked the perfect one out. I read that speakers are typically 6 to 8 ohms. The 4 ohm ones require a larger amp to drive it. This makes sense. These speakers are rated for 30W RMS at 8 ohms. My amp is only 14W so I won't blow the speakers. There is a lot of 'rules of thumb' when it comes to audio as there are a lot of people trying to put in crazy sound systems in their Honda Civics. I do not understand the fascination with that car and it is so over priced for what it is. One rule of thumb I found was that the speaker power rating should be twice that of the amp. This makes sense to me though I found others that said the opposite. I think those other people have blown a few speakers. To summarize, get the 8 ohm, not he 4 ohm or you will draw too much power from your amp.
If you have clicked on any of the links bar the one for the op-amp, you will see that I purchased from Newark. They were recommended to me. I am still waiting on my order but it has only been a couple of days.
Just quickly, to update on the solenoid driver board I've been working on the schematics for it. I am at least doing a better job of documenting my work. I will be posting the schematics and my first board layout soon. Due to the board sized limitation on EagleCad freeware, I can only fit (at least I think I can) the circuitry to drive six solenoids. I am fine by this. It makes my solenoid power distribution more modular. I will likely use three boards for 18 solenoids. The EagleCad freeware is limited to a board size of 8 x 10 cm. I could have used KiCad as it is unlimited but from what I have heard it is not as user friendly and everyone has EagleCad which makes sharing much easier. I think I will try KiCad out in the future when the limitations of EagleCad frustrate me enough but the biggest problem I found with it was finding complete libraries for components. Maybe I'm missing something, I do not know. In any case, more posts coming.
Now for the audio mixer and amplifier. I found this circuit diagram and I am planning on using the bottom right one. Instead of the two mono channels, I will change them to a third stereo input.
I will be using the following components for this circuit:
MC33202 - Low Voltage Rail to Rail Operational Amplifier
PDB182-K425K-103A - 10 KOhm Rotary Pot (Log/Audio Taper)
P160KNP-0EC15A25K - 25 KOhm Rotary Pot (Log/Audio Taper)
SPC21349 - Audio Jack
This is the amp that I will be using. The circuit diagram is provided in the datasheet:
TDA7269A - 14W Audio Stereo Amplifier
My speakers:
4899 - Viston Speaker 8 Ohms 30W RMS
I think I may have made a mistake on the speakers or perhaps picked the perfect one out. I read that speakers are typically 6 to 8 ohms. The 4 ohm ones require a larger amp to drive it. This makes sense. These speakers are rated for 30W RMS at 8 ohms. My amp is only 14W so I won't blow the speakers. There is a lot of 'rules of thumb' when it comes to audio as there are a lot of people trying to put in crazy sound systems in their Honda Civics. I do not understand the fascination with that car and it is so over priced for what it is. One rule of thumb I found was that the speaker power rating should be twice that of the amp. This makes sense to me though I found others that said the opposite. I think those other people have blown a few speakers. To summarize, get the 8 ohm, not he 4 ohm or you will draw too much power from your amp.
If you have clicked on any of the links bar the one for the op-amp, you will see that I purchased from Newark. They were recommended to me. I am still waiting on my order but it has only been a couple of days.
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