Pics of my HRM Funk Build

[tele_player]

CW = clockwise
CCW = counter clockwise

[Structo]

OK, that was my first thought, but how does that relate to the hookup?
IOW, what lug on the pots would CCW be?

Any thought on the quenching diodes?

[odourboy]

OK, that was my first thought, but how does that relate to the hookup?
IOW, what lug on the pots would CCW be?

Any thought on the quenching diodes?

Diodes are the norm. I used 1N4007 which is probably overkill (but hey, they were handy). 1N4001 would be fine I'm sure.

[mlp-mx6]

I don't know if I did this correctly or not, but...

In 3 different amps I have taken a 7812 regulator, drilled a hole in the chassis, gone to RadioShack and bought a TO-220 mounting kit (screw, nut, sleeve, and mica insulator), and mounted the regulator to the chassis. The 3 legs of the regulator I soldered to a small terminal strip and bolted that to the chassis also. I get 12V solid, even with 5 relays and 3 LED active. (or with 3 12AX7s lit...)

[tele_player]

Sounds like you did it right.

[odourboy]

Sounds good. FWIW, the tab on the package is hardwired to the common (center) leg, which is normally connected to ground. If you're using your chassis as a ground, you can skip the insulator and just bolt her straight to the chassis. In which case you can even skip connecting up the center leg.

[Deric]

Also, while I can read a schematic, anybody have a layout of the PS and relay board that I could simply copy rather than try to figure out one for myself?

There is a layout over at the Brown Note forum in the for sale thread (Relay PCBs For Sale). I am working on a regulated relay power supply layout that should be up in a couple of days also.

[tele_player]

Really?

[stelligan]

odourboy-

Great looking build. I'm jealous!!


Deric -

When you're up and running on those boards again, please let me know.

Thanks,
Dave

http://brownnote.net/forum/viewtopic.ph ... lay+boards

[skyboltone]

Better pull all those sand diodes out of there, too - right?

Maybe a definition of Brute Force regulation is in order. It's not a "no engineering solution at all, and was practiced universally to power low voltage low current devices for many years. For all I know, it is still used in Simplex Fire Alarm systems because the approval procedures are so cumbersom and old methods die hard in old industries.

The object is to provide a power supply source with enough current handling capability or "stiffness" that the use of dropping resistors to regulate voltage at the loads does not upset the supply or run loads too far from design center. I would not use a single dropping resistor in the + lead to a pair of relays. Instead, I would use a dropping resistor at each relay. I'm not sure what Aharon's relays draw, but it's common for these little ones being used to draw about 5 ma to activate and hold the coil. So lets say that we've got 7.5VDC coils and a 14 volt supply. We need to loose about 6.5VDC in a dropping resistor to provide energy to the coil. R=E/I = 1.3K. So what does this do to our supply. Lets say that the 14 volts comes from a 6.3 volt 3 amp transformer and a voltage doubler. Our unregulated 14 volt supply is good for about 1.35 amps. The 5ma relay coil should have a DC resistance of about 1500 ohms. When we combine these two resistances (2800ohms) across a 14 volt supply we still have about 5ma. Using two relays, how much does 10ma upset a 14 volt supply at 1.35 amps? The loads represent just under 4% of the available supply. It should work fine.

I use sand/solid state stuff all the time. I use a darlington transistor to multiply the power handling capability of a little $.04 zener diode to 150W at the center tap of the High Voltage windings of my power transformers to drop a few volts. And of course in the power supply and any place else it seems appropriate.

To imply that the only measure of good engineering is parts count is simply wrong. In the mean time I'll go back and edit my post regarding engineering practice and your relationship to it Tele-Player.

Dan H

[tele_player]

Yes, I understand what brute force regulation is. The doubler referenced above doesn't quite make it. As you point out, the single dropping resistor is a problem. The capacitance is also too low to hold the DC voltage steady under load.
Anyway, brute force regulation only makes sense when there isn't a better alternative. In this case, a well-regulated supply is simpler and cheaper.
BTW, the coil current for the ultra-sensitive Omron 5V is 30ma. This is much higher than your estimate, and makes it more difficult to sufficiently stiffen the power supply.
I'm tired of this pissing match. You jumped up in defense of an inferior design, and haven't refuted my assertion that it can be done cheaper and better with a regulator.
The parts list for a voltage doubler with 8V regulator is 2 caps, 2 diodes, 1 regulator, and an optional .1uF on the output of the regulator, recommended in the regulator's datasheet. About $2-$3 total, for a rock-solid supply, and about the same for a regulated 12V supply using a 12v transformer.
I don't see any compelling reason NOT to regulate these supplies.

[Aharon]

I started this debate by asking what the value of "R" would be for the non regulated PS.
Deric was gracious enough to give me the value of 30R that he used for 3 relays.
I was going to use 2 relays so I needed to adjust it,my Ohms law was a little rusty or I was lazy to look and I asked.
All this cause I was in a rush to finish my amp plus I did not want to etch another board etc.

I will go with the regulated supply but I thank you for the help.

Not worth arguing over this guys....
Aharon

[Structo]

I think the value is 56R for the PS resistor, that is with two relays and non-regulated supply.

[Aharon]

Yeah,I tried with a 56R yesterday and it dropped enough voltage that I think the 5V relay would be happy,you pointed me to that value,thank you.
Aharon