Want to know operation of this Schematic

[BradtheRad]

You will have to test the components and find out whether they cooperate.

Simulations are one thing. Plans on paper are one thing.

Reality is another thing.

 

[sr_raval]

Oh okay means there is a no chance to operate the relay from 22VDC to 26VDC supply range? by rearranging the circuit? or it may operate when i am testing the circuit practically on breadboard ?

 

[BradtheRad]

The charge pump automatically creates a few volts drop.

You can operate on 26 V because the relay coil will get 23V or so and that is sufficient...

almost certainly on 25 or 24V, because the coil will get 21 to 22V, and a relay will usually operate when the coil gets above 90 percent of its rated V...

but at 23 or 22V you are in an uncertain region because the coil is getting 19 to 20 V.

Since this is your project, you will have to decide what step you need to take from here.

All I've been doing is playing with simulations.

 

[sr_raval]

yes i understand insort i think i will get idea when i will check circuit preactically on breadboard, as my relay operating voltage is 18VDC so it might be a chance to drive relay via 22VDC to 26VDC.

 

[sr_raval]

But still i have one question is if my relay having 18VDC operating voltage then it has to be operate on 22VDC supply, let me know your thoughts on this.

 

[BradtheRad]

An 18 or 20V relay should work properly if the supply is 22VDC (at top left of the schematic).

Your link to the relay datasheet is for a rating of 24V, I notice.

My relay datasheet is https://www.te.com/catalog/pn/en/2-1393190-8

There is a reason for the UL specification of +2 or -2 V. It is meant to ensure your device will operate at times when mains AC drops a few volts due to brownout, or appliances loading the circuit, variations in your component values, etc.

 

[sr_raval]

Yes i know thats why i am trying operate charge pump relay drive circuit at 22VDC, have you noticed 24VDC relay operating voltage 18VDC they have mentioned, then why its not possible to operate via 22VDC i am just curcious to know the reason.

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Yes i know thats why i am trying operate charge pump relay drive circuit at 22VDC, have you noticed 24VDC relay operating voltage 18VDC they have mentioned, then why its not possible to operate via 22VDC i am just curcious to know the reason.

 

[BradtheRad]

have you noticed 24VDC relay operating voltage 18VDC they have mentioned

I did not see this at the link with the datasheet. A search on '18' turned up nothing.

However if you saw a spec saying that the 24V relay will operate on 18V, then I have no basis to say it won't.

 

[sr_raval]

check it i have highlight the text

 

[BradtheRad]

I looked at the link you gave:

ENG_DS_1308242_T7C_0411[1].pdf

It does show 18V as the operating voltage.

As long as that applies to your relay, then you probably can continue as planned.

 

[sr_raval]

yes i will try to implement the same circuit by using above mentioned relay and try to observe the result? once i will get some outcome i will update you.

One more thing have you worked on pressure tranducer? can i use one pressure transducer for two diffrent drives?

 

[BradtheRad]

Sorry, I have no experience with pressure transducers.

If you start a new thread with the words 'pressure transducer' in the title, and post a diagram of what you want to do, then you may get replies.

 

[sr_raval]

Yes i am planning to do so thanks Brad

 

[sr_raval]

Brad,

1) I am tesing that circuit on breadboard but i am little bit confuse for the positions of capacitor (+ and -), here i am attaching the circuit which i have implemented, please let me know if its correct or not? if not kindly make the necessary change.
2) one more thing i am preparing design document for this circuit for that i require the theoritical calculation of each compoenent, how you have select the value of resistors,capacitors, op-amps, transistors and diodes? could you please elaborate on this? it really helps me integrate every scenario in my document, furthermore it helps me to understand the circuit in detail.

Thanks

 

[BradtheRad]

how you have select the value of resistors,capacitors, op-amps, transistors and diodes? could you please elaborate on this?

The op amps, transistors and diodes are 'generic' in the simulator. You must select them for ability to withstand volt levels at the supply, inputs, and output.

While watching the simulation, I saw the totem-pole zener diodes passing current at times when it caused improper operation in the circuit. I found it was because they needed to have a higher volt threshold. I experimented until I found a threshold that appeared to work in all situations, including with a 26 V supply.

Resistors in general were selected to conserve current, so that more milliamps were available to go to the relay coil. In small signal networks, values from 1k to 10k tend to be satisfactory.

Capacitors required fiddling with values. They should be large enough to pass sufficient current. Some ripple is tolerable, so I reduced them to obtain maybe 5 percent ripple.

The inputs at the first op amp need to be in a range that will reliably create the desired output. I experimented with resistor values to find ones that suit.Same with the second op amp.

I chose the third zener to have the same value as the other zeners, to make things easy.

I chose the resistors on the op amp outputs, to be high enough to pass just a few mA, yet low enough so they would reliably operate the transistors.

Nothing says these values are infallible. I just play with the simulation. No doubt there are unknown factors ahead which will affect operation with real components.

By the way, you can experiment with the simulation too. It's all part of the testing process.

 

[sr_raval]

Sorry i forget to attach the scan copy to identify polarity of capacitor, go through attached file currently i have connected all capacitor in this manner. do let me know if require any modification in this.

How did you calculate the value of C1 R7 D4 & C2, R8, D5 & R9, C3 ?? because all those components are RC charge circuit

 

[BradtheRad]

Sorry i forget to attach the scan copy to identify polarity of capacitor, go through attached file currently i have connected all capacitor in this manner. do let me know if require any modification in this.

How did you calculate the value of C1 R7 D4 & C2, R8, D5 & R9, C3 ?? because all those components are RC charge circuit

Your schematic came through okay.

You show all capacitors with correct polarity.

R7 and R8 should be large enough ohms to prevent false relay closing when power is first connected. The ohm values work in my simulation. You must experiment with real components.

C1 and C2 only need to be large enough to provide adequate current, in the form of pulses. When I saw a small amount of ripple voltage, I figured they were the right value. If you make them larger, they are more expense, and take up more space.

All the capacitors should be rated for the power supply V you will connect to this project.

D4 & D5 are not special. You can use ordinary 1A rating, at 50V reverse rating.

R9 and C3 serve to stabilize volt levels in the right half of the circuit, especially at the op amp inputs. R9 & C3 smooth spikes and surges. It's vital to have such safeguards to prevent false relay closings.

It all depends on how bad the spikes and surges are. R9 may need to be reduced. C3 may need to be increased. This is something I cannot predict with a simulator.

 

[sr_raval]

One news is from my end is that, circuit is operating well, currently I am performing FMEA and risk analysis on the circuit. I have following questions please have a look on that. Consider above attached schematic
1) What’s the need and function of R2, R3, R4 & R5?
2) What’s the need and function of R10, R11, R12 & R13?
3) Functionality of D1 & D?
4) Functionality of D8?
5) And Most importantly how you have finalize the C1 & C2 and R7 & R8 value? On the basis of any theoretical equation? Please share the fundamental equation

 

[FvM]

Brad, do it again!

 

[BradtheRad]

Brad, do it again!

I accept the good-natured ribbing.

At some point in this thread I did ask myself, will anyone in their home be harmed (or avoid harm) if I continue (versus bow out from) helping this project along?

Hearing that this relay driver might be installed in people's furnaces, I decided I should continue.

- - - Updated - - -

One news is from my end is that, circuit is operating well, currently I am performing FMEA and risk analysis on the circuit. I have following questions please have a look on that. Consider above attached schematic
1) What’s the need and function of R2, R3, R4 & R5?
2) What’s the need and function of R10, R11, R12 & R13?
3) Functionality of D1 & D?
4) Functionality of D8?
5) And Most importantly how you have finalize the C1 & C2 and R7 & R8 value? On the basis of any theoretical equation? Please share the fundamental equation

1.

R2-3-4-5 form something like a wheatstone bridge (a basic type of measuring network). It is a reliable method so the op amp can detect when the clock is high and low.

2.

R10-11-12-13 form a wheatstone bridge. It lets the op amp detect whether the right-hand power supply is sufficiently high to trigger activation of the transistor T4, which activates the relay. The zener diode is essential to create a regulated volt level.

3.

D1 & D2 cooperate with C1 & C2, to create a bridge (Greinacher) voltage doubler.

4.

By D8 do you mean D3? (There is no D8 that I find.) D3 is the diode which is customarily installed across a relay coil. It absorbs spikes that might occur when power is cut to the coil.

Spikes do not appear to happen in this circuit. Power drops gradually, not suddenly, at the relay coil.

Nevertheless the diode should be left in as a safeguard.

5.

C1 & C2 should permit just enough current as will permit operation at normal supply voltage. Same with R7 & R8.

There is no benefit to making C1 & C2 larger than they need to be. I could only experiment with their values, until I found values that work, at the frequency coming from the clock pulses.

Same with R7 & R8. They should be higher ohms if possible. You should test and find out.

If you were to raise the frequency of clock pulses, it is possible you could further reduce C1 & C2.

From what I can see, the reason so many components are used to activate one relay is to (a) stop operation when supply V drops below 23 V or so, and (b) break all direct contact of the relay to electrical power when it is not operating.

I believe this is the line of reasoning behind the UL code specifications.

C1 & C2 are essential in this purpose. In one respect they block DC from getting to the relay when it should be off. Then C1 & C2 are involved in the voltage doubler operating.