Speaker Turn On Delay and DC Protector Board Set (V3)

[escucalin]

Originally Posted by turion64

Hi folks...I just finished building the speaker protect circuit using the 12VDC relays. The center tapped transformer I bought to power the circuit ( supposed to have been 12-0-12, TRIAD F-45X) measures 29VAC across the two outside secondaries. I tried it out anyway. The circuit’s LED did what they were supposed to do (wow what a rapid blinking) and the speaker input-outputs has continuity after the relays clicked on. My question is if the 29VAC will be too much for this circuit/relays over time and should I seek a slightly lower output transformer, say 24-26VAC?

Thanks! Pete

Hello Pete,

A 29V AC would go to 40V after rectification and a bit of filtering.
Maybe using a LM317 to bring down the utility rail to 24V would spare you the expense of another trafo.

[turion64]

Thanks, I will explore that..I measured 29VAC in (whether under the circuit load or not) and 17VDC across pins 2&5 of each of the relays. The stats sheet says the relay can handle 170% of max rated voltage so I’m assuming that means each relay can actually handle up to 20.4 VDC?

Originally Posted by escucalin

Hello Pete,

A 29V AC would go to 40V after rectification and a bit of filtering.
Maybe using a LM317 to bring down the utility rail to 24V would spare you the expense of another trafo.

[escucalin]

Originally Posted by turion64

Thanks, I will explore that..I measured 29VAC in (whether under the circuit load or not) and 17VDC across pins 2&5 of each of the relays. The stats sheet says the relay can handle 170% of max rated voltage so I’m assuming that means each relay can actually handle up to 20.4 VDC?

Their consumption is very low,
Would be better to power them with 11V not 17V for a reliable coil life

A regulator can fit on a wire if nicely shrink wrapped and even include a 200mA resetable fuse.



But hey if it works ... you have my 2 cents

[turion64]

I’m grateful for your input, really. Some questions though: so would this be an appropriate resettable fuse (mouser; 530-0ZRR0010FF1E)? For setting 24V out of the LM317 I could use 180R for R1 (between ADJ and Vout pins) and 3.3K for R2 (from ADJ to neutral/return wire of AC line)? Heat sink needed? Where would the resettable fuse be connected?

Thanks, Pete

Originally Posted by escucalin

Their consumption is very low,
Would be better to power them with 11V not 17V for a reliable coil life

A regulator can fit on a wire if nicely shrink wrapped and even include a 200mA resetable fuse.



But hey if it works ... you have my 2 cents

[escucalin]

Originally Posted by turion64

I’m grateful for your input, really. Some questions though: so would this be an appropriate resettable fuse (mouser; 530-0ZRR0010FF1E)? For setting 24V out of the LM317 I could use 180R for R1 (between ADJ and Vout pins) and 3.3K for R2 (from ADJ to neutral/return wire of AC line)? Heat sink needed? Where would the resettable fuse be connected?

Thanks, Pete

The fuse protects the circuit from accidents si it can go a bit higher .. 500mA

It goes right after the transformer output .


The voltage regulator resistor values are good See here : LM317 Resistor and Voltage Calculator


It does not need sinking under 200mA or so the circuit draws.


So go nuts on the shrink tube and enjoy!