Boards ready for testing.
Next step is to connect some power and see what happens.
What kind of programmer are you using?
I'm using this programmer:
FTDI Basic 6 Pin 3 3 5V for Arduino Free USB Cable | eBay
I expected to run into problems with FTDI drivers, especially since I run Win10 that don't aske any questions before updating things, but so far so good.
Maybe the pirates have found a workaround to trick the drivers into believing it's a genuine FTDI chip?
FTDI Basic 6 Pin 3 3 5V for Arduino Free USB Cable | eBay
I expected to run into problems with FTDI drivers, especially since I run Win10 that don't aske any questions before updating things, but so far so good.
Maybe the pirates have found a workaround to trick the drivers into believing it's a genuine FTDI chip?
Your adapter may actually be using a real FTDI chip, but FTDI can't seem to tell the difference. I had them brick some products that had genuine FTDI chips on them, so I'm not going to design using their products any more. This is one company I hope the pirates drive out of business. I can't support a company that destroys some poor kids legitimate new toy.
I've got some adapters using the CP2102 UART adapter waiting for testing.CP2102 USB 2 0 to TTL UART Module 6pin Serial Converter STC Replace FT232 Module | eBay There seems to be no standard footprint to the connection to these and they can't seem to get the reset line right, so I'm planning to design my own rear panel connector board with these installed in them. The QFN-28 looks a little scary to install, but actually goes quite well.
I've got some adapters using the CP2102 UART adapter waiting for testing.CP2102 USB 2 0 to TTL UART Module 6pin Serial Converter STC Replace FT232 Module | eBay There seems to be no standard footprint to the connection to these and they can't seem to get the reset line right, so I'm planning to design my own rear panel connector board with these installed in them. The QFN-28 looks a little scary to install, but actually goes quite well.
I have a suggestion for a new feature. How about a clipping indicator? I like to build my amps fool proof so that I don't destroy anything even when I'm drunk.
A I2C clipping indicator would be nice. The front panel led could flash during clipping and then the speaker could be disconnected if you continue to clip for more then 10 seconds. Drunk mode
I guess this could be integrated in the dc detect board.
A I2C clipping indicator would be nice. The front panel led could flash during clipping and then the speaker could be disconnected if you continue to clip for more then 10 seconds. Drunk mode
I guess this could be integrated in the dc detect board.
Last edited:
Here's the next step in the move to external interface for the amplifier. I've got a proper USB to serial adapter running. It uses the CP2102 USB to UART bridge, which operates at 3.3V. I added proper level shifting for communicating to 5V devices, and some ESD filtering and level shifting on the USB connection. It uses a old style USB B connection, so it's tougher to break too. It should mount nicely into a rear panel for a permanent connection.
Attachments
With requests like Yngves last one, they might need to be! Alcohol induced clipping protection shouldn't be too hard to add, but I think it might be neat to have it interface with a preamp, and automatically adjust the volume.
At the moment this is just going to be a programming interface. We need to be able to communicate with other devices without slowing down the monitoring of the protection systems, so we should be offloading this onto some other device. Using the serial monitor window for example, uses a bunch of interrupts to do the communication with the PC, so there would be short lapses in the monitoring while it passes each bit to the PC.
I've been messing around with a preamp design that uses separate Atmega328s for each part of the preamp, one to read an encoder, one for front panel, one for volume control... If that works well, I'll look into applying the same idea here.
I've got test boards layed out for I2C current monitoring too, but I'm hesitant on relying on them as a main current monitoring sensor, because it can't be directly connected to an interrupt on the Atmega328, but they would give you an actual current reading, as opposed to a good/bad reading. They might be a good redundant add on.
I've been messing around with a preamp design that uses separate Atmega328s for each part of the preamp, one to read an encoder, one for front panel, one for volume control... If that works well, I'll look into applying the same idea here.
I've got test boards layed out for I2C current monitoring too, but I'm hesitant on relying on them as a main current monitoring sensor, because it can't be directly connected to an interrupt on the Atmega328, but they would give you an actual current reading, as opposed to a good/bad reading. They might be a good redundant add on.
I've got a bit further since the last time around, but at the moment I've got a failed DC/speaker relay board, and the system keeps tripping out when in my AV room.
This may well not be the right forum, but I'm wondering if the tripping is because my power supplies for both the amp and control are floating. Should the 0V leads of the transformer be earthed to the chassis earth?
I've noticed the trips seem to be either overload or DC as the light is flashing constantly and rapidly. Normally they are caused by any component in the system being turned on or off such as the TV. One time it was when I connected the cable coax input to the set to box. I should be said in the less harsh environment of my office where its connected via a DAC to my laptop, I've not seen any unexpected events.
I've also got one perfectly functioning DC protect board and one broken one, I'm going to do some diagnostics on that separately. On my scope I'm seeing that at low volumes it outputs nothing, but as the power increases, it starts to output a half wave signal. I suspect either a bad MOSFET or opto.
It should be said despite these issues it's functioning (sans one DC protect) in the office.
Thanks,Dave
This may well not be the right forum, but I'm wondering if the tripping is because my power supplies for both the amp and control are floating. Should the 0V leads of the transformer be earthed to the chassis earth?
I've noticed the trips seem to be either overload or DC as the light is flashing constantly and rapidly. Normally they are caused by any component in the system being turned on or off such as the TV. One time it was when I connected the cable coax input to the set to box. I should be said in the less harsh environment of my office where its connected via a DAC to my laptop, I've not seen any unexpected events.
I've also got one perfectly functioning DC protect board and one broken one, I'm going to do some diagnostics on that separately. On my scope I'm seeing that at low volumes it outputs nothing, but as the power increases, it starts to output a half wave signal. I suspect either a bad MOSFET or opto.
It should be said despite these issues it's functioning (sans one DC protect) in the office.
Thanks,Dave
The amp and the control board are optically isolated from each other allowing them to work with floating grounds. Your amplifier star ground should be connected to chassis ground through a ground loop breaker for safety though.
Rapid flashing of the LED means DC protection tripped it. Overload will show as a slowly flashing LED.
One thing to try is operating the amplifier one channel at a time and verify which channel is bad, them swap the speaker relays and try again. This will tell you for sure if it's the speaker relay acting up. The issue could be a cold solder joint in the speaker relay, but what you are describing actually sounds like an unstable amplifier channel.
I've attached a wiring scheme that shows how your amplifier ground should be connected to earth ground.
Rapid flashing of the LED means DC protection tripped it. Overload will show as a slowly flashing LED.
One thing to try is operating the amplifier one channel at a time and verify which channel is bad, them swap the speaker relays and try again. This will tell you for sure if it's the speaker relay acting up. The issue could be a cold solder joint in the speaker relay, but what you are describing actually sounds like an unstable amplifier channel.
I've attached a wiring scheme that shows how your amplifier ground should be connected to earth ground.
Thanks Jeff, given I've got one working channel and one faulty I can compare by switching the board over as you said. Comparing output between the two.
But before proceeding further with diagnosis I will build the safety earth circuit as safety comes first. Do the diodes in star earth safety have to be high current or should they be signal types?
But before proceeding further with diagnosis I will build the safety earth circuit as safety comes first. Do the diodes in star earth safety have to be high current or should they be signal types?
The grounding diodes need to be high enough current handling to be able to blow the mains fuse/breaker without damage. A 30 amp bridge is usually used. http://ca.mouser.com/ProductDetail/...=sGAEpiMZZMtQ8nqTKtFS/LDhWhDI65nsPTtCZsZfMvU=
On a couple of the speaker protect boards I put together I needed to increase the time delay between turning on the amp and checking for DC at the output. They were for some reason a bit more sensitive and the amps needed a couple more seconds to settle before the board would except that DC was OK and connect the speaker. I tried multiple speaker protect boards on the same amp channel... some tripped some didn't. All the boards were built using parts from the same "bags"
I designed these to be very sensitive to DC (+/- 1.2 - 1.6V trip points). Some may be a little too sensitive due to part variations, but I've actually never been able to make any of my prototypes, or installed versions to false trigger. I designed some newer SMT versions that operate at much lower current and had some issues with them false triggering when more than one relay engaged at the same time. I've got that figured out, and have some through hole versions of the same design waiting for testing.