12volt check

Hi,

Check out maxim's voltage monitoring chips at their websites.

Bye

Big House wrote:

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Use LM324 for the OpAmp, making sure that its VDD is at least 2V higher than the largest desired input.

...Jim Thompson

-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | |

It can be done with only two OpAmps, but I'll "leave that as an exercise for the student" ;-)

...Jim Thompson

You can control indefinitely large loads with a relay- but some of them are fussy about 25% overdrive so you have to current limit. View in a fixed-width font such as Courier.

. . . Vin>---+---+------+--------+-------+-------o---v . | | | | *| o----->Vout . | | | | [Re] . | | | >| | | . | | | 2N3906 |-----+ . | | | /| | | . | | [10k] | | . | | | | |< | . | [10k] +--------+-----| 2N4403 . | | | |\\ | . | | [2.7k] | . | | | +--|Vout . | | | | [22] . | | | >| | | . | | | 2N4403 |-----+ . | | | /| | | . | | [10k] | | . | | | | |< | . | [10k] +--------+-----| 2N4403 . | | | |\\ | . | | [2.7k] | . | | | +--|

Probably. The relay idea will do that. Also Bloggs has a submission, which I'm sure works ;-)

...Jim Thompson

-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | |

This Bloggs bloke is OK aint he

martin

Well- if a relay is required then he needs to current limit at 15V, like so: View in a fixed-width font such as Courier.

. . . . . Vin>---+---+------+----------------+ . | | | | . | | [10k] | . | | | |< . | [10k] +--------------| 2N3906 . | | | |\\ . | | [5.6k] | . | | | +--|Vout . | | 10k | | . === / POT | | . 0.1u| \\ --- | . | / ---+---+------+--------+-------+-------o---v . | | | | *| o----->Vout . | | | | [Re] . | | | >| | | . | | | 2N3906 |-----+ . | | | /| | | . | | [10k] | | . | | | | |< | . | [10k] +--------+-----| 2N4403 . | | | |\\ | . | | [2.7k] | . | | | +--|

You can control indefinitely large loads with a relay- but some of them are fussy about 25% overdrive so you have to current limit. View in a fixed-width font such as Courier.

. . . Vin>---+---+------+--------+-------+-------o---v . | | | | *| o----->Vout . | | | | [Re] . | | | >| | | . | | | 2N3906 |-----+ . | | | /| | | . | | [10k] | | . | | | | |< | . | [10k] +--------+-----| 2N4403 . | | | |\\ | . | | [2.7k] | . | | | +--|Vout . | | | | [22] . | | | >| | | . | | | 2N4403 |-----+ . | | | /| | | . | | [10k] | | . | | | | |< | . | [10k] +--------+-----| 2N4403 . | | | |\\ | . | | [2.7k] | . | | | +--|

Something like this provides a sharp turn-on/off: View in a fixed-width font such as Courier.

. . . . . Vin>---+----+----------+------------+----+ . | | | | | . | | | [10k] | . | | | | |< . | | .----|---[4.7k]---+--| 2N3906 . | | | | _ |\\ . | [470] | | /| | . | | | [10k] | . | | \\| /| | . === |2N3904 |--+-----[22k]--|Vout . 0.1u| +------

for

because my

valves I

will

using

Here's a pyro-electrically triggerd unit

Eric

And you don't need the stop diode for the relay circuit: View in a fixed-width font such as Courier.

. . . Vin>---+---+------+--------+-------+-------o---v . | | | | | o----->Vout . | | | | [22] . | | | >| | | . | | | 2N4403 |-----+ . | | | /| | | . | | [10k] | | . | | | | |< | . | [10k] +--------+-----| 2N4403 . | | | |\\ | . | | [2.7k] | . | | | | | . | | | | _ . | +------|-[100K]---------+--------|/| . | | 10k | | |/| 12VDC . === / POT | - |/| 400mW . 100u| \\ --- 1N4001 ^ |_| . | / ---+----+-----+----+---------+-------+---------+ +-->Vout . | | | | | | | | . | | | | | [22] | | . | | | | >| | | | . | | | | 2N4403|-----+ | | . | | [10k] | /| | -|---|- . | | | | | |< | | | | . | | +----|---------+-----| 2N4403 |COM NO | . | | | | _ |\\ | | . | [470] [4.7k] | /| | | | . | | | [10k] | | | . | | \\| /| | | | . === |2N3904 |--+---[22k]---------+-------|--O O---+ . 100u| +------

It works fine at 1Hz, or at DC, if a separate floating power supply is created for the HI-side driver section. A few years ago I posted the schematic of a high-speed 250V 50-ohm pulse generator using this approach with an IR2113, a chip with similar MOSFET drivers.

But theyre happy with 20% underdrive, so can just use a series resistor to translate 12-15v to 9.6-12v.

NT

Resistor and 12V zener to the base of a transistor driving a relay.

Cheers.

Ken

Hmmm... what am I doing wrong? I breadboarded it, and I get about 1.3 Vout when under threshold with threshold anywhere from 5 to 12 volts and a 17 volt supply. (Didn't try above

It's a nice circuit. Like they say in the cereal commercial: "Mikey likes it!"

Ed

You're not doing anything wrong, it seems to be working as the OP requested ;-)

It can be done with only two OpAmps. Has anyone figured out how yet?

...Jim Thompson

_- 1n ----+-----+------+----o~. o------------> out | | | . | | | ______ | \\6K8 |___| _-~|_____. / / | |_-~ | | 10K \\ \\ | ~~~~~~ | / / +-----|----[2K2]--| 5.1V | | | / |\\ __L_| +----| / | \\| |/^\\ | |/| ~\\ | / | | | \\ | | | / | | | \\ 5k1 | | | | | | | | | | ------+-----+------+----------------+-

for the relay and transistor it depends on the load you want to switch.

if high precision and temperature stability is needed a precision voltage source could be used instead of the zener diode