Author Topic: High side switch question  (Read 5819 times)

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Online digsys

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Re: High side switch question
« Reply #25 on: April 08, 2017, 10:17:44 am »
Quote from: neo
How should they be oriented?
Vertical, Pin#1 to the top. Mercury must cover the contacts. Check the specs. It will still work horizontal but you won't get the full 2-5B operations.
On 1 site, I calculate 25B clicks (at 10Hz), 24/7, 5-8yrs
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Offline neo

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Re: High side switch question
« Reply #26 on: April 08, 2017, 11:12:45 pm »
Well that is certainly convenient, my entire clock is vertical due to the display.
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Online digsys

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Re: High side switch question
« Reply #27 on: April 08, 2017, 11:33:46 pm »
Sample pack of ~12 is ready to post :-)  2x new, 2 types, rest are swap-outs, and should still have ~50+M closures. Just test for dead ones.
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Offline Zero999

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Re: High side switch question
« Reply #28 on: April 09, 2017, 12:33:08 am »
This is another way to do it, besides with an optocoupler which should be straightforward as another alternative.

]
It's better to move the NPN's base resistor to the emitter and add a pull-up on the PNP. It's much faster and has a higher input impedance.

 
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Offline SeanB

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Re: High side switch question
« Reply #29 on: April 09, 2017, 04:49:18 pm »
Added bonus is that there is no digit ghosting from amplified base current leakage as well, so you can use the Vces voltage instead of the Vceo voltage.
 
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Offline neo

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Re: High side switch question
« Reply #30 on: April 12, 2017, 05:12:28 am »
This idea is completely irrelevant it doesn't work. I tried it.
« Last Edit: April 12, 2017, 07:57:05 am by neo »
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Online digsys

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Re: High side switch question
« Reply #31 on: April 12, 2017, 05:27:23 am »
Naaaaa, there's nothing good about that circuit AT ALL ! With the NPN on, you have 4.4V/220R current draw, for no reason. Do either one of the NPN/PNP solutions, or the NPN/Relay
solution. Use ~2K2 to NPN base, and the relay to 12V. That way there is no OFF current. You can put a 100-220R in series with the relay coil to reduce draw even further.
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Offline neo

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Re: High side switch question
« Reply #32 on: April 12, 2017, 06:32:06 am »
I must be terrible at this everything i can get my head around makes little to no sense in practice it seems. Will a tip 137 work for the pnp in the npn pnp solution? I know it is overkill but i got one. Also going into the specifics of the simulator, it says there little current draw current so either falstad is wrong or its missing a law of physics, im not trying to be annoying just trying to understand
« Last Edit: April 12, 2017, 06:56:52 am by neo »
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Online digsys

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Re: High side switch question
« Reply #33 on: April 12, 2017, 06:46:10 am »
Quote from: neo
I must be terrible at this everything i can get my head around makes little to no sense in practice it seems. Will a tip 137 work for the pnp in the npn pnp solution?I know it is overkill but i got one.
Don't panic, it gets easier with time and practice. Just about ANY PNP will do. The TIP137 is a darlington, so you'll lose ~1V, which should be perfectly OK.
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Offline neo

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Re: High side switch question
« Reply #34 on: April 12, 2017, 07:19:51 am »
I didn't panic at all the first 3 months, now i panic alot because the more i learn the more confused i get.  :-DD |O :scared:
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Offline neo

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Re: High side switch question
« Reply #35 on: April 22, 2017, 12:25:50 am »
I tried the pnp high side and found this circuit to work well. Yes, that really is a germanium.
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Offline Zero999

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Re: High side switch question
« Reply #36 on: April 22, 2017, 12:29:56 am »
I tried the pnp high side and found this circuit to work well. Yes, that really is a germanium.
Yes, that should work fine in real life too.

The only issue might be speed, with such high value resistors, otherwise it's a good idea.

By the way, why did you decide on a germanium transistor? Is it just because it's cool to use old parts?
 

Offline neo

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Re: High side switch question
« Reply #37 on: April 22, 2017, 02:06:49 am »
Its germanium because it was handy. Its for a 1 hertz signal, i physically built it and it worked well.
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Offline brunoital

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Re: High side switch question
« Reply #38 on: April 22, 2017, 03:39:37 pm »
Schematics?
 

Offline Zero999

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Re: High side switch question
« Reply #39 on: April 22, 2017, 04:18:02 pm »
Schematics?
Plenty of schematics have been attached to the posts. You'll need to be logged in to the forum to see them. If you are having problems viewing them, check your firewall settings.
 

Offline Zero999

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Re: High side switch question
« Reply #40 on: April 23, 2017, 06:44:45 pm »
Here's another option which only uses one NPN transistor.

« Last Edit: April 23, 2017, 07:01:02 pm by Hero999 »
 

Offline sanwal209

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Re: High side switch question
« Reply #41 on: April 23, 2017, 09:17:21 pm »
Make life simple, There are tons of IC load switch and cost you 44 cents. Try this one out
https://www.digikey.com/product-detail/en/vishay-siliconix/SI1865DDL-T1-GE3/SI1865DDL-T1-GE3TR-ND/4494407
 


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