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nishant's β24+α10 integrated amp build log

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Re: nishant's β24+α10 integrated amp build log

Postby Pinnocchio » September 27th, 2013, 6:46 pm

Be careful with large VA toroids and SSR... If you're using the Plitron transformer exactly as in the b24 project you will be fine since it is very well shielded but I have tried with less expensive transfos and there huge mecanical hum from the transfo (not really audible in the speakers) and loud enough to hear it from your listening position. You can read about SSR and large transfos but I have done many experiments using Crydom SSR and had to remove them and use a mechanical relay which then was perfect, the transfo became totally quiet. I tested this with 4 different transfos and two different brands with same results. Even the mightly Plitron is making a very small amount of noise with it but very low noise. I attached a mechanical relay on it and it became totally dead silent!

If you still want to use a SSR, I have a barely used one I can sell to you. It is the same one as in the B24. It was used for less than 2 hours in a different Class A amp.

Ciao!
Do
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Re: nishant's β24+α10 integrated amp build log

Postby tommarra » September 30th, 2013, 7:31 am

dsolodov wrote:My understanding is LCDuino is 5VDC, and the listed Omron relay needs 12VDC for the coil and the listed Crydom SSR needs >= 3VDC. What will source the 12 VDC for Omron relay?


Whew. Thanks for catching that! I am sure I would have built the power supply and then wondered why is the amp not working the way it should :-)

amb wrote:Good catch, dsplodov. A 5V relay is needed there.



Since I dont have a 12V power source, can I use a 12VDC wall off the shelf power supply to power the bleeder relays. (Since with I don't need the momentary switch functionality). Do you think this would be safer and less error prone?

Something like this: http://www.amazon.com/Power-Adapter-Sup ... 12+v+power

The bleeder relay should draw 0.1A (1.2W nominal could power at 12V) so the cheapo power supply should be good..right?

B24+A10 Power control - Alternate.jpg



Alternatively, I can use the following 5V bleeder relay

http://www.mouser.com/ProductDetail/Pan ... f1TyiXQ%3d

Please advice!!!

Also Ti, on the thermal breakers, where do you place them, somewhere close to the Beta 24 boards, power supply or both?




Pinnocchio wrote:Be careful with large VA toroids and SSR... If you're using the Plitron transformer exactly as in the b24 project you will be fine since it is very well shielded but I have tried with less expensive transfos and there huge mecanical hum from the transfo (not really audible in the speakers) and loud enough to hear it from your listening position. You can read about SSR and large transfos but I have done many experiments using Crydom SSR and had to remove them and use a mechanical relay which then was perfect, the transfo became totally quiet. I tested this with 4 different transfos and two different brands with same results. Even the mightly Plitron is making a very small amount of noise with it but very low noise. I attached a mechanical relay on it and it became totally dead silent!

If you still want to use a SSR, I have a barely used one I can sell to you. It is the same one as in the B24. It was used for less than 2 hours in a different Class A amp.


Thanks Do...this information is very insightful. I have already ordered the SSR from Mouser. Let me see how it behaves in my build. I am using Richard Sumr's encapsulated toroidal trafo, Hoppefully it wont have a lot of hum.

Although I wonder what causes the hum from the trafo when using a SSR? Any thoughts?
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Last edited by tommarra on September 30th, 2013, 8:53 am, edited 4 times in total.
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Re: nishant's β24+α10 integrated amp build log

Postby Pinnocchio » September 30th, 2013, 7:57 am

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Re: nishant's β24+α10 integrated amp build log

Postby amb » September 30th, 2013, 12:05 pm

Using a separate wallwart seems so inelegant... Also, depending on how you wire it, if the wallwart loses power while the amp is on, the bleeder resistors will smoke and the relay may be damaged.

How about using two Omron G6B-2014P-US DC5 relays? Each one has two DPST-NC contacts which you should connect in parallel to increase the contact current capacity. This relay is also relatively inexpensive. They are for PCB-mount, though, so you'll have to fashion a little mounting board to hold the relays and connectors suitable for wires. Don't forget that the two relays coils in parallel adds about 80mA of load to the 5V supply, so you need to size the transformer accordingly.

The thermal breakers should be mounted to the main heatsinks near the output MOSFETs.

Btw, the links Pinnochio provided explains why there may be a large turn-on surge with SSRs and inductive loads, but it does not explain why the transformer would mechanically hum continuously while it's on. If you're concerned about the surge current, use a non zero-crossing version of the SSR.
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Re: nishant's β24+α10 integrated amp build log

Postby tommarra » September 30th, 2013, 1:05 pm

amb wrote:Using a separate wallwart seems so inelegant... Also, depending on how you wire it, if the wallwart loses power while the amp is on, the bleeder resistors will smoke and the relay may be damaged.

How about using two Omron G6B-2014P-US DC5 relays? Each one has two DPST-NC contacts which you should connect in parallel to increase the contact current capacity. This relay is also relatively inexpensive. They are for PCB-mount, though, so you'll have to fashion a little mounting board to hold the relays and connectors suitable for wires. Don't forget that the two relays coils in parallel adds about 80mA of load to the 5V supply, so you need to size the transformer accordingly.


Thanks Ti for the reply.

Based on yours and others responses I have created two more schematics for my power supply. Would you please take a look when you get a chance.

Option#1 : Use two Omron G6B-2014P-US DC5 relays in parallel. The main concern is the capacity of the S25 to support LCDuino and 2 D1, 2-D2 boards as well as the three relays. My transformer is a 25VA toroidal, so I am confident that the transformer will not be the limiting factor in this configuration. But I worry that S25 / LCDuino itself be the limiting factor.

In S25 write up, Ti has mentioned that S25 not be used for more than 300mA continuous load. Will the S25 while powering all the other components as well as the three relays get overwhelmed. Also I must add, given the discussion about SSR and Transformer noise I would rather have an EMR for the B24 power transformer primary.

EMR I plan to use: TE Connectivity KUHP-5DT1-12
http://www.mouser.com/ProductDetail/TE- ... 2frA%3d%3d

Also in this case is LCDuino in any danger of damage, given that all the current is being supplied by the LCDuino boards for all the downstream parts (2- D1s, 2- D2s and the relays?)

Here is the schematic based on Ti's previous feedback.

Power Supply AMB Solution.jpg


Option 2:

The other option is very similar to the reference E24 solution that Ti has used in his build. All I am doing is replacing the E24 with an S25 (since I do not need the switching capabilities).

This way even is the second 12V S25 fails, all electrical circuits will switch off and protect the bleeder resistors.

Another advantage of this is that I already own the Crydom SSR 558-CL240D05 that will act as the load for the SSR output from LCDuino.

All the relays would be EMRs to get rid of the transformer hum issue.

Power Control - All EMR - Separate Power Supply.jpg


Question: Any thoughts as to why I should go with Option 1 vs Option 2 and vice versa?


Thanks in advance

Question 2: Also is the TE connectivity relay fit for purpose - its rated at 30A which I think should be plenty given my transformer is 500VA (~ 5 amp on full load).

amb wrote:The thermal breakers should be mounted to the main heatsinks near the output MOSFETs.


Got it Thanks!!!
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Re: nishant's β24+α10 integrated amp build log

Postby amb » September 30th, 2013, 1:43 pm

Option 1 is not feasible for two reasons:

1. The LCDuino-1's SSR control port can supply only 40mA, and all the EMRs' combined coil current would exceed that. In fact only one of the Omron G6B relays would exceed it. This problem existed in the original proposal you posted but I didn't notice it (just as I didn't notice that the relay coil voltage was wrong).
2. The LCDuino-1's SSR control port is 5V TTL logic level (5V "high"), but the TE Connectivity relay has a 12V coil so it won't be activated.
In order to do option 1, you can use a "buffered relay" (i.e., with onboard transistor drive), see the last few posts in the SSR Help! thread. Then, use this relay to drive the additional relays needed to switch the β24 main power and for the bleeder resistors. You will still need a 5V relay for the main power, though.

Option 2 is ok as far as I could see, although it's getting really complicated requiring an extra 12V power supply.

The σ25 "300mA" advisory is really more for thermal concerns than anything else. The voltage regulator is capable of handling 1A (or 1.5A, depending on whose datasheet you read). If you need the σ25 to supply more current than 300mA, then you should mount the voltage regulator vertically, rather than folded down against the board, and use a larger heatsink on it.
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Re: nishant's β24+α10 integrated amp build log

Postby tommarra » September 30th, 2013, 1:52 pm

Thanks Ti. You are awesome as always!

Let me research the SSR Help thread you mentioned and find if I can get a transistor buffered relay on the cheap.

I would rather not complicate and use a second power supply...so I hope I can get some appropriate buffered relay.

All else failing I will go with Option 2.
AMB Projects built: B22 (Active ground), S22, S25, LCDunio, D1, D2, A20
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Re: nishant's β24+α10 integrated amp build log

Postby Pinnocchio » September 30th, 2013, 7:54 pm

I really don't know why the transformers were making such a big hum noise but the transformers I tested were SumR encapsulated and Antek. SumR are totally quiet transformers otherwise. Was the SSR passing some DC that the transformers didn't like? Don't know...

Ciao!
Do
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Re: nishant's β24+α10 integrated amp build log

Postby tommarra » October 1st, 2013, 8:43 am

amb wrote:Option 1 is not feasible for two reasons:

1. The LCDuino-1's SSR control port can supply only 40mA, and all the EMRs' combined coil current would exceed that. In fact only one of the Omron G6B relays would exceed it. This problem existed in the original proposal you posted but I didn't notice it (just as I didn't notice that the relay coil voltage was wrong).
2. The LCDuino-1's SSR control port is 5V TTL logic level (5V "high"), but the TE Connectivity relay has a 12V coil so it won't be activated.
In order to do option 1, you can use a "buffered relay" (i.e., with onboard transistor drive), see the last few posts in the SSR Help! thread. Then, use this relay to drive the additional relays needed to switch the β24 main power and for the bleeder resistors. You will still need a 5V relay for the main power, though.



Hi Ti,

Looked around on Amazon and found this http://www.amazon.com/gp/product/B00CHI ... os_product

Is this what you (and the other thread) you were referring to?

So the S25, sends VCC and GND to this board. And LCDuino sends SSR Control via J6 terminal block, that will turn on / off this module.

However I have a problem: Per the schematics, I believe that the relay is energinzed when SSR Out is low. I think LCDUino sends +5 for turning on the SSR ..am I correct?

schematic.png


I can wire the relay so that when de-energized the circuit between S25 and forward relays (for power transformer and bleeder) is complete. But this would mean that whenever I switch off the amplifier from LCDuino, this relays on this board will be energized and consume power...and possibly fail.

Am I getting something wrong here?

If not is there a way for to modify LCDuino's SSR out signal so that ON = Low and Off = High?

I started looking at the Volumaster Firmware and found the folliowing code. If I reverse the High / Low in the turn_on_spkr_power_relay() and turn_off_spkr_power_relay(), will I get the desired beheviour from SSR Out signal on LCDuino? (maybe I should ask this in the LCDuino forum):
---------------------------------------------------------------------
void
turn_on_spkr_power_relay (void)
{
#ifdef USE_X10
if (option_x10_firecracker == 1) {
X10_turn_spkr_power_on();
}
#endif

#ifdef USE_POWER_RELAY
digitalWrite(RELAY_POWER_PIN, LOW);
#endif

return;
}





void
turn_off_spkr_power_relay (void)
{
#ifdef USE_X10
if (option_x10_firecracker == 1) {
X10_turn_spkr_power_off();
}
#endif

#ifdef USE_POWER_RELAY
digitalWrite(RELAY_POWER_PIN, HIGH);
#endif


--------------------------------------------------------------------------------------
Alternatively,

I also found this relay:

http://www.sainsmart.com/arduino-compat ... -1280.html

I think that it closes when a high signal is sent.


Also I notices that this relay
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Re: nishant's β24+α10 integrated amp build log

Postby amb » October 1st, 2013, 12:17 pm

Answered in this post since you asked in multiple threads: controlling-relay-extension-module-w-lcduino-t2422.html#p21948

The SainSmart mdule does have "normal" logic, but its relays' contacts are not rated high enough to handle the bleeder resistors directly like the Zitrades module.
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