How to increase current capability without changing R1 (2M) or R2 (1M) in LED circuit?

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#1 21665230 12 Dec 2012 01:01

Earl Albin Earl Albin

Anonymous

Post #1
21665230 12 Dec 2012 01:01

The diode symbols are diacs symbols which means when the input voltage reaches the combined 3-x voltage the diacs will fire. If the resistances is too high the holding current isn't enough and the diacs will turn off, like a relaxation oscillator. It appears the remaining diac is if the circuit is connected in reverse it will fire through D7.

Why do you want more current? What is the problem you are trying to solve?
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#2 21665231 12 Dec 2012 01:05

George Capka George Capka

Anonymous

Post #2
21665231 12 Dec 2012 01:05

I have been asked to find a way have more current capability without increasing the resistance of R1 and R2... the circuit is meant to be a High Voltage sensor. Thanks for any tips
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#3 21665234 12 Dec 2012 01:09

Earl Albin Earl Albin

Anonymous

Post #3
21665234 12 Dec 2012 01:09

Yes but you didn't explain what your objective is, more current for what? Sure you could decrease the value of the resistors but then the DIACS might have enough to stay on and defeat the purpose of the circuit.

What specifically are you wanting more current for? Do you know? There are way to amplify current but without understanding what the problem is that you are trying to solve it is difficult to advise because you might create a new problem that doesn't exist. That's what Engineering is.
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#4 21665232 12 Dec 2012 01:09

Earl Albin Earl Albin

Anonymous

Post #4
21665232 12 Dec 2012 01:09

Yes but you didn't explain what your objective is, more current for what? Sure you could decrease the value of the resistors but then the DIACS might have enough to stay on and defeat the purpose of the circuit.

What specifically are you wanting more current for? Do you know? There are way to amplify current but without understanding what the problem is that you are trying to solve it is difficult to advise because you might create a new problem that doesn't exist. That's what Engineering is.
#5 21665233 12 Dec 2012 01:09

Earl Albin Earl Albin

Anonymous

Post #5
21665233 12 Dec 2012 01:09

Yes but you didn't explain what your objective is, more current for what? Sure you could decrease the value of the resistors but then the DIACS might have enough to stay on and defeat the purpose of the circuit.

What specifically are you wanting more current for? Do you know? There are way to amplify current but without understanding what the problem is that you are trying to solve it is difficult to advise because you might create a new problem that doesn't exist. That's what Engineering is.
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#6 21665235 12 Dec 2012 01:12

George Capka George Capka

Anonymous

Post #6
21665235 12 Dec 2012 01:12

We are trying to see if we can add components to the circuit but they seem to have a higher current requirement than what we can handle at the moment with the current configuration.... we are trying to keep the design secret. Any ideas on increasing current will help and be used for research. Thanks
#7 21665236 12 Dec 2012 01:17

Earl Albin Earl Albin

Anonymous

Post #7
21665236 12 Dec 2012 01:17

I have to know what the source is capable of supplying 1st. 2nd I am not interested in stealing your secrets.

So with the extra current, how much are we talking about. Those DIACS, what are the firing voltages?
#8 21665237 12 Dec 2012 01:20

George Capka George Capka

Anonymous

Post #8
21665237 12 Dec 2012 01:20

Maybe increase the current capability of the circuit by around 25 percent?
Each Diac is 26 V firing
#9 21665238 12 Dec 2012 01:29

Earl Albin Earl Albin

Anonymous

Post #9
21665238 12 Dec 2012 01:29

Here is what doesn't make sense with the circuit. You have two paths, one is 75V (3x 25V DIACS) then you have the second path is 28V (1 DIAC & 3 LED). the LED path will always fire 1st. The 3 DIAC path will never get to 75V. What is that path for?

The reverse path is 26V, actually a 3rd path, will fire at about 26V.
#10 21665239 12 Dec 2012 01:37

George Capka George Capka

Anonymous

Post #10
21665239 12 Dec 2012 01:37

hello?
#11 21665240 12 Dec 2012 02:11

Earl Albin Earl Albin

Anonymous

Post #11
21665240 12 Dec 2012 02:11

What I am looking at, there is no Q7, there are 4 DIACS on regular diode, 3 LEDs and two resistors.

You want to increase the current, yea sure lower the two resistor values. You get what you get. Now keep that a secret.

Get someone else to help you, You are wasting my time!!!!
#12 21665229 12 Dec 2012 02:23

George Capka George Capka

Anonymous
Post #12
21665229 12 Dec 2012 02:23

Any ideas without having to increase the value of R1 or R2 (they are 2M and 1M each)?
D1 , D2, D3 are diodes that let voltage pass when its 24V or above.. the LEDs are just indicators of High Voltage... the more voltage the more they lit.

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#13 21665241 12 Dec 2012 02:25

George Capka George Capka

Anonymous

Post #13
21665241 12 Dec 2012 02:25

I just came to this forum for help not for having someone questioning what I am trying to do. Now with all due respect .... is there anyone out there who can give me ideas on how to increase the current capabilities of a circuit that would be great, Thank!!
#14 21665242 12 Dec 2012 02:28

George Capka George Capka

Anonymous

Post #14
21665242 12 Dec 2012 02:28

h
#15 21665243 12 Dec 2012 03:53

Frank Bushnell Frank Bushnell

Anonymous

Post #15
21665243 12 Dec 2012 03:53

There is no circuit diagram showing on your message at present, only an image that says, "CAN ANYONE HELP ME PLEASE".
Would you like to re-post the diagram ?
#16 21665244 12 Dec 2012 14:18

Steve Lawson Steve Lawson

Anonymous

Post #16
21665244 12 Dec 2012 14:18

Ditto [reminds me of finding a message in a fortune cookie that reads "Help! I'm being held prisoner in a Chinese laundry!!"]
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Topic summary

✨ The discussion centers on increasing the current capability of a high voltage sensor circuit without altering the resistor values R1 (2MΩ) and R2 (1MΩ). The circuit uses DIACs as triggering elements, each with a firing voltage around 26 V, arranged in multiple paths including a 75 V path (three DIACs in series) and a 28 V path (one DIAC and three LEDs). The main challenge is that high resistance limits holding current, causing DIACs to turn off prematurely, resembling a relaxation oscillator. Suggestions to increase current by lowering resistor values were rejected to maintain circuit function and secrecy. The exact current increase target is approximately 25%. The lack of a detailed circuit diagram and the secretive nature of the design complicate providing specific solutions. The discussion highlights the need to understand the source current capability and the firing voltages of DIACs to propose effective current amplification methods without compromising the circuit’s intended operation.
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FAQ

TL;DR: In this HV sensor, one path breaks at ~75 V while the LED path triggers near ~28 V—so LEDs fire first. Expert note: “The 3 DIAC path will never get to 75V.” [Elektroda, Earl Albin, post #21665238]

Why it matters: If the low‑threshold path always triggers, adding parts for “more current” won’t work without rethinking thresholds; this FAQ shows how, for hobbyists and engineers diagnosing DIAC‑LED sensors.

Quick Facts

R1 = 2 MΩ, R2 = 1 MΩ; the design targets a high‑impedance HV sensor front end. [Elektroda, George Capka, post #21665229]
Each DIAC fires around 26 V; three in series sum near 75–78 V. [Elektroda, George Capka, post #21665237]
Competing paths: ~28 V path (1 DIAC + 3 LEDs) triggers before the ~75 V path (3 DIACs). [Elektroda, Earl Albin, post #21665238]
Requested headroom: about +25% more current capability. [Elektroda, George Capka, post #21665237]
Lowering divider resistance increases current, but may keep DIACs latched and defeat the sensor’s intent. [Elektroda, Earl Albin, post #21665234]

What’s actually happening in this DIAC–LED HV sensor?

Two threshold paths compete. The LED path has one DIAC plus LEDs (~28 V), so it triggers first. The three‑DIAC path needs ~75 V and never reaches breakover while the lower path conducts. Result: LEDs light and the higher‑voltage path stays idle. [Elektroda, Earl Albin, post #21665238]

Can I increase current without changing R1 (2 MΩ) or R2 (1 MΩ)?

Within this divider‑driven topology, the forum advice was clear: more current comes from lower resistance. Keeping R1/R2 fixed preserves the very low source current, so added loads will starve the DIACs or relight cyclically. “You get what you get” unless you redesign the front end. [Elektroda, Earl Albin, post #21665240]

Why might high resistances make the DIACs chatter or switch off?

If the charging path is too resistive, the DIAC’s holding current isn’t met. It turns off after breakover and the node recharges, creating relaxation‑oscillator behavior and unstable indication. That’s classic DIAC operation when current is limited. [Elektroda, Earl Albin, post #21665230]

What are the actual resistor values and purpose here?

R1 is 2 MΩ and R2 is 1 MΩ. The high values form a high‑impedance divider to sense HV while limiting current into the DIAC/LED network. This preserves safety margin but severely limits drive for added components. [Elektroda, George Capka, post #21665229]

What is a DIAC, in plain terms?

A DIAC is a bidirectional trigger diode that stays off until its breakover voltage, then conducts and latches until current drops below a holding value. Typical breakover is about 30 V. [“DIAC”]

What current increase did the OP want, and what were the DIAC thresholds?

They asked for roughly a 25% increase in current capability. Each DIAC had a 26 V firing voltage, so three devices imply about 78 V for that branch. [Elektroda, George Capka, post #21665237]

Why do the LEDs always light first in this schematic?

Because the LED branch includes one DIAC plus LED drops, it reaches about 28 V and fires earlier than the three‑DIAC branch at ~75 V. Early conduction clamps the node, blocking the higher‑threshold path. [Elektroda, Earl Albin, post #21665238]

Could adding more LEDs or parts boost current capability?

Adding parts raises load current. With a 2 MΩ/1 MΩ divider, available current is tiny. Extra load risks dropping below DIAC holding current, causing flicker or oscillation instead of more drive. [Elektroda, Earl Albin, post #21665230]

Is there a general spec for DIAC breakover I can use for estimates?

Typical DIAC breakover is 30–40 V per device. That statistic helps budget thresholds and decide path priority before you add or move components. [“DIAC: The bidirectional diode”]

I want help but don’t want to reveal the full design. Any advice from the thread?

State measurable targets (e.g., +25% current), thresholds, and constraints (R1/R2 fixed). That enabled replies without IP disclosure and kept discussion productive. [Elektroda, George Capka, post #21665241]

How do I debug competing breakover paths in three quick steps?

List each path’s total breakover: count DIACs and LED drops; compute thresholds.
Measure node voltage rise with the divider; confirm which path triggers first.
Remove or raise the lower threshold path to test if the higher path can fire cleanly. [Elektroda, Earl Albin, post #21665238]

What if my DIACs say 26 V but someone mentioned 24 V in the thread?

The OP clarified their DIACs fire at 26 V. Any earlier 24 V mention referred to allowing pass above about 24 V in that drawing. Use the actual device spec for design math. [Elektroda, George Capka, post #21665237]

A reply said, “lower the two resistor values.” Why might that defeat the purpose?

Lowering R1/R2 increases current, but it can also keep DIACs latched on, changing a threshold sensor into a continuously conducting path. As one expert put it, “That’s what Engineering is.” [Elektroda, Earl Albin, post #21665234]

What if the community can’t see my schematic?

You’ll get little actionable help. One user noted the image only said “CAN ANYONE HELP ME PLEASE.” Always re‑post a clear diagram to speed diagnosis. [Elektroda, Frank Bushnell, post #21665243]

Do typical DIACs support higher current loads directly?

DIACs are triggers, not drivers. They supply a sharp pulse after breakover; you still need a load path that honors holding current and your divider’s limits. Consider external drivers only after threshold conflicts are resolved. [“Tutorial on DIAC”]

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