x******9
发帖数: 203 | 1 用现有的0V/0.5V DC输出 控制 110VAC, 1A的交流电路
要求当控制输出由0.5V变成0V时，切断交流电路起到保护的作用 |
c*******l
发帖数: 4801 | 2 弄个amplifier把这个0.5V变成5V,然后drive个开关？
【在 x******9 的大作中提到】
: 用现有的0V/0.5V DC输出 控制 110VAC, 1A的交流电路
: 要求当控制输出由0.5V变成0V时，切断交流电路起到保护的作用
|
p***o
发帖数: 216 | 3 找个合适的继电器(relay)就可以，不过你的控制高电平比较小，也许要放大一下。
【在 x******9 的大作中提到】
: 用现有的0V/0.5V DC输出 控制 110VAC, 1A的交流电路
: 要求当控制输出由0.5V变成0V时，切断交流电路起到保护的作用
|
d****s
发帖数: 26 | |
x******9
发帖数: 203 | 5 我也是这么考虑的，现在relay有了，需要至少5V驱动，
请问放大电压用什么器件比较合适呢？关键参数是什么？
【在 p***o 的大作中提到】
: 找个合适的继电器(relay)就可以，不过你的控制高电平比较小，也许要放大一下。
|
f*****0
发帖数: 489 | 6 0.5v trigger is tough to do, as it wouldn't be enough to turn on a bjt.
a few posibilities:
a) you can use some depletion mosfet which conducts at all voltage types.
b) you can use a comparator, preferrably single rail type. like lm311.
c) form a 0.2 - 0.5v supply, and apply it to the base of a npn bjt. type
emitter of your bjt to your control signal, and your relay to the collector.
when the control signal is at 0.5v, the be junction doesn't get enough
signal to turn on the bjt so the relay sta |
f*****0
发帖数: 489 | 7 the problem with using a depletion type mosfet is that most of those devices
don't have a clear turn on threshold. they gradually turn on and this can
be a death knoll in a switching application like yours. |
f*****0
发帖数: 489 | 8 another approach may be to use some low power 555. the 2 triggers go off at
1/3 and 2/3 of Vcc so if you can get some 555 that runs on 1v Vcc you would
have a solution. |
f*****0
发帖数: 489 | 9 another solution is to use germanium transistors. those suckers turn on at 0
.2v vs. 0.6v for a silicon transistor.
that is an almost perfect solution for you: germanium transistors don't turn
completely on. but you can use it to drivea mosfet / silicon tansistor.
the old 3ax31 from China probably go for cents now, and nte has a lot of
germanium transistors. |
g******u
发帖数: 3060 | 10 check for some logic gate chips, some should have amplifier built inside. |
b*****e
发帖数: 1193 | |
f*****0
发帖数: 489 | 12 the problem is the 0.5v threshold. very few amps will be trigger by that
kind of voltage.
to "amplify" it, you will have to solve the power supply issue for such a
voltage.
the best alternative I think is a germanium transistor; then a comparator (
but you will have to solve interference issue so the comparator doesn't flip
accidentally). |
h**e
发帖数: 9290 | 13 pmos input can handel 0-1V easily with 3V or 5V supply.
Using a differential PMOS inputs amplifier with negative-side set to 0.25V,
0 input will leads to ~5v output and 0.5V input will leads to ~0V ouput.
Althought gain could be low, it is good enough to make logic transition. |
f*****0
发帖数: 489 | 14 mosfet typically has Vgs threshold at 3.5v, p-channel or n-channel. using it
always requires setting up a voltage, which I am not sure is superior. |
