Ok, I think I will get this show on the road by taking 76 units and we reach our 100 needed for production. I will set up a pre-order listing in my shop to collect the funds to start this. I am going with a new assembly house this time and they are promising much faster turn around time.
For those who did not commit to the GB2, the pricing of the item in the shop may be a little higher since I had to cover the costs of the majority of the production.
For those who did not commit to the GB2, the pricing of the item in the shop may be a little higher since I had to cover the costs of the majority of the production.
Pre-orders are now being taken here:
RTR SSR Speaker Protection Gen2 | Etsy
Please add a note when placing order what your DIYA screen name is.
Thanks,
X
RTR SSR Speaker Protection Gen2 | Etsy
Please add a note when placing order what your DIYA screen name is.
Thanks,
X
Is the listed price for one channel board? have to purchase 2 for stereo setup, right?
X, Is the draft v1.9 schematic of post 447 referred to above the final schematic for the Version 2? If not, can you post the final schematic please?
I like to know exactly what's going into my builds.
Thanks
Gen 2 RTR SSR schematic attached below.
A simple switch can be put across J1 as a mute switch. Or use an open collector logic from a micro controller to operate the remote shutoff using X1.
A bonus break-away board that is unpopulated for TH components will let one make their own instant off controller; connect X2 to X1.
Screenshot of PDF:
Render of PCB with free breakaway board (unpopulated):
A simple switch can be put across J1 as a mute switch. Or use an open collector logic from a micro controller to operate the remote shutoff using X1.
A bonus break-away board that is unpopulated for TH components will let one make their own instant off controller; connect X2 to X1.
Screenshot of PDF:
Render of PCB with free breakaway board (unpopulated):
Attachments
Last edited:
Thanks.
Regarding the breakout board for obtaining fast-off, is the idea to power the DC regulator from the breakout board (which accepts AC from the transformer's secondary) in lieu of DC from the amp's +ve rail?
Next, regarding the power dissipation of the regulator, the NCP781 doesn't publish an SOA curve or a maximum power rating, oddly. Instead, it publishes RθJA thermal resistance of 125 °C/W and maximum junction temperature of 150 C and provides thermal shutdown. This RθJA is based on a copper area of 645 mm2 (or 1 in2) of 1 oz copper thickness and FR4 PCB substrate. (Your board may have more area.)
Well, it appears the NCP781is running near its max junction temperature for a 250 Watt amp. Such an amp has about 65v rails, minus 15v at the load leaves 50v across the NCP781. At 20 ma this is 1 Watt. Amps internally run hotter than 25 C. I assume 40 C. Adding 40 C internal temperature to 125 C rise from from 1 W is 165 C, apparently exceeding the allowed junction temperature.
What did I get wrong?
Whereas (assuming I'm doing this right) in a 100 W 8R amp with 42v rails we appear to be okay with 27v and 20ma across the NCP781 for .54 watts. Junction temperature would be 40 C + 68 (125*.54) C = 108 C.
To cool things down, can we feed the regulator with a big zener in series?
Thanks again
Regarding the breakout board for obtaining fast-off, is the idea to power the DC regulator from the breakout board (which accepts AC from the transformer's secondary) in lieu of DC from the amp's +ve rail?
Next, regarding the power dissipation of the regulator, the NCP781 doesn't publish an SOA curve or a maximum power rating, oddly. Instead, it publishes RθJA thermal resistance of 125 °C/W and maximum junction temperature of 150 C and provides thermal shutdown. This RθJA is based on a copper area of 645 mm2 (or 1 in2) of 1 oz copper thickness and FR4 PCB substrate. (Your board may have more area.)
Well, it appears the NCP781is running near its max junction temperature for a 250 Watt amp. Such an amp has about 65v rails, minus 15v at the load leaves 50v across the NCP781. At 20 ma this is 1 Watt. Amps internally run hotter than 25 C. I assume 40 C. Adding 40 C internal temperature to 125 C rise from from 1 W is 165 C, apparently exceeding the allowed junction temperature.
What did I get wrong?
Whereas (assuming I'm doing this right) in a 100 W 8R amp with 42v rails we appear to be okay with 27v and 20ma across the NCP781 for .54 watts. Junction temperature would be 40 C + 68 (125*.54) C = 108 C.
To cool things down, can we feed the regulator with a big zener in series?
Thanks again
The add on board provides the open collector signal to shutdown the SSR even if it’s powered by the main (high capacitance) PSU rail. You are probably correct about the regulator exceeding the thermal limit for a high voltage rail. We should advise us of some sort of voltage dropper zener as you suggest for higher voltages. I’ll let Jhofland reply in more detail though. I have used it with 53v rail and it has been ok. Just warm not not. The board probably has an effective area larger than 1 in square.
@charliemb,
The low capacitance little breakout board is intended to supply a 3mA current for the external enable input on the new version speaker protection. When AC power is shut off this supply will collapse well within 100 milliseconds to shut the speaker protection SSR off before the main supply decays.
The low capacitance little breakout board is intended to supply a 3mA current for the external enable input on the new version speaker protection. When AC power is shut off this supply will collapse well within 100 milliseconds to shut the speaker protection SSR off before the main supply decays.