# 555 supply voltage

#### salty joe

Joined Dec 14, 2010
43
The pumps I want to build a controller for are DC 24 volt, 30 watt. I need to control two pumps with one controller.

As I was reading the tutorial for the 555, I found the supply voltage is between 4.5 and 19 volts.

Will a 555 not work for this project?

#### Wendy

Joined Mar 24, 2008
22,170
Not without interfacing. There are ways to do it, such as the one I'm about to show for a relatively high frequency oscillator by way of example. The 555 controls a transistor, which in turn interfaces to the high voltage side.

BTW, a standard 555 can only handle 4.5VDC to 15VDC, while a CMOS 555 (totally different part) can usually handle 3.0VDC to 18VDC. The 19VDC is an internet myth, datasheets are your friend.

#### salty joe

Joined Dec 14, 2010
43
Wow! Thank you Bill, for the schematic. I printed it and will study and learn how to read it. I am completely impressed that you can whip something like that out. Also impressed with your generousity.

BTW, I enjoyed the interview with Hans Camenzind, that was a fun little read. Now I have to read the rest. It is a slog for sure-this stuff is hardly second nature for me, trying to wrap my head around it one little chunk at a time. The good old divide and conquer routine.
Oh, and I almost fell out of my chair when I saw a 555 FOR 13 CENTS!!! Almost unbeleivable!

#### Yako

Joined Nov 24, 2011
245
a 555 FOR 13 CENTS!!!
I have been quoted less in recent times, much, much less in fact for a moderate quantity. But I cannot tell you exactly how much though, for obvious business reasons.

13-cents would have some of these guys in tears, if they have a large quantity of them. RRP for this IC used to be well above the one-dollar mark for the TTL and much more for the CMOS version.

#### Yako

Joined Nov 24, 2011
245
@Bill

Radio Shack 1982 -- how much for a NE555?

#### Wendy

Joined Mar 24, 2008
22,170
Don't know, currently it is about $1.50 or so. My price is generally 35¢ #### SgtWookie Joined Jul 17, 2007 22,220 In 1982, Radio Shack was selling the 555 timer for$0.99.
They were $1.49 in 1976 - however, you could also get an assortment of 50 untested ICs for$1.29.

#### Wendy

Joined Mar 24, 2008
22,170
Wayback machine?

#### thatoneguy

Joined Feb 19, 2009
6,359
In 1982, Radio Shack was selling the 555 timer for $0.99. They were$1.49 in 1976 - however, you could also get an assortment of 50 untested ICs for $1.29. You could also buy a gallon of gas for$0.80 in 1982

#### Yako

Joined Nov 24, 2011
245
I thought that they would have been like 3-dollars or more.

#### Yako

Joined Nov 24, 2011
245
My toy CRO has one

How fast are they good for?

I always wanted a feature-packed clock pulse generator in a nice case.

• 1MHz
• Variable amplitude
• Variable frequency in ranges
• Sweep ...
• Astable or monostable
Maybe you can design something good.

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#### Yako

Joined Nov 24, 2011
245
Like a nice sturdy powder-coated case with lots of knobs and switches.

Are they good for giving a decent square at 1MHz with low rise and fall times?

#### Wendy

Joined Mar 24, 2008
22,170
You could also buy a gallon of gas for \$0.80 in 1982
Except that was the era of the gas shortage, Jimmy Carter for President.

#### salty joe

Joined Dec 14, 2010
43
Not without interfacing. There are ways to do it, such as the one I'm about to show for a relatively high frequency oscillator by way of example. The 555 controls a transistor, which in turn interfaces to the high voltage side.

BTW, a standard 555 can only handle 4.5VDC to 15VDC, while a CMOS 555 (totally different part) can usually handle 3.0VDC to 18VDC. The 19VDC is an internet myth, datasheets are your friend.
As I read about the 555, I got the impression that all 555s are not quite the same. Would this 555 (NE555 IC 555 TEXAS INSTRUMENTS DIP-8 Timer) be a good choice for my pump controller? Or would I be better off using a CMOS 555?

#### Wendy

Joined Mar 24, 2008
22,170
The specs do very a little depending on manufacturer, by about a volt or so, but in general a conventional 555 is 4.5VDC-15VDC, while a CMOS 555 is 3V-18V. However, I have run some CMOS 555's as low as 2V, though I would not recommend it.

#### salty joe

Joined Dec 14, 2010
43
OK thanks, I'll get a small quanity of the Texas Instruments 555 to play with.

The 7 pin from the 555 is not on your schematic, will I need to put a dab of silicone adhesive on the 7 pin to protect it?

I am about ready to order the parts for this dual pump controller but am not sure what transistors to buy. Any help there would be greatly appreciated.

There are two open circles-one at the 3 pin on the 555 and the other at the top of the schematic. Do the open circles represent shielded cable?

#### thatoneguy

Joined Feb 19, 2009
6,359
There are two open circles-one at the 3 pin on the 555 and the other at the top of the schematic. Do the open circles represent shielded cable?
No, that's an indicator for an inverted output. So when you would think the output is "high" it's actually low, and vice versa. Carried over from digital logic.

#### SgtWookie

Joined Jul 17, 2007
22,220

The 7 pin from the 555 is not on your schematic, will I need to put a dab of silico
ne adhesive on the 7 pin to protect it?
Pin 7 is simply not used in the scheme that Bill drew.

Note that in Bill's schematics, when more than 2 wires intersect, there is a black dot which signifies a junction. If two wires cross each other and there is no black dot, the wires are simply crossing each other and there is no connection. If there is a black dot, the wires are connected.

I am about ready to order the parts for this dual pump controller but am not sure what transistors to buy. Any help there would be greatly appreciated.
It looks like your motors are 24V, 1.25A (30W). Are you planning on driving them with 24v, or with 30v as Bill has shown?

You could use a TIP120 Darlington, but it would be preferable to use an N-ch MOSFET.

There are two open circles-one at the 3 pin on the 555 and the other at the top of the schematic. Do the open circles represent shielded cable?
The open circle at pin 3 simply means that the output is inverted from the input; the inputs being pins 2 and 6.

The open circle at the top of the schematic is simply a terminal where the source voltage would be connected.

#### salty joe

Joined Dec 14, 2010
43
The label on the pump says DC 24V, 1.3A, 30W. Does not quite add up, is the best thing to assume 31.2W?

Since the pump is listed at 24V, 24V seems like the way to go but I don't know. Will driving them at 30W wear them out quicker?

If transistor N-ch MOSFET is prefferable, that's what I'll get. All four transistors would be the same?

Just want to make sure-this controller will drive two of these pumps, is that right?

Thank You very much.
Joe