Timeline for Inductive and resistive load current draw - PSU
Current License: CC BY-SA 4.0
24 events
| when toggle format | what | by | license | comment | |
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| Jan 24, 2020 at 21:59 | history | rollback | ElectronSurf |
Rollback to Revision 1
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| Jan 24, 2020 at 21:58 | history | rollback | ElectronSurf |
Rollback to Revision 2
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| Jan 24, 2020 at 20:52 | vote | accept | ElectronSurf | ||
| Jan 24, 2020 at 18:13 | comment | added | ElectronSurf | @CristobolPolychronopolis Oh sorry I get it now, I meant it's configured as an comparator not an actual comparator. | |
| Jan 24, 2020 at 17:36 | answer | added | D.A.S. | timeline score: 1 | |
| Jan 24, 2020 at 17:18 | comment | added | ElectronSurf | @CristobolPolychronopolis So what is your suggestion? how can an op amp switch to current mode? how I can compare the reference voltage and the current other than using a comparator? | |
| Jan 24, 2020 at 17:09 | comment | added | Cristobol Polychronopolis | @ElectronSurf A comparator isn't the right tool here, unless your plan is to switch the supply on and off rapidly like a buck regulator. Its output is basically digital. An op amp will work better. The reason your feedback circuits aren't doing much is because they have a high impedance compared to what's driving the negative input (output voltage in one case, op amp output direct in the other). | |
| Jan 24, 2020 at 15:59 | comment | added | ElectronSurf | @CristobolPolychronopolis It's a comparator, can't just connect the non-inverting input to the output. even removing that RC doesn't solve the problem. | |
| Jan 24, 2020 at 15:54 | comment | added | Cristobol Polychronopolis | Your buffer on the output has no DC feedback path due to the 1uF cap. That'll keep the slew rate down, but it's still infinite gain at DC. | |
| Jan 24, 2020 at 15:48 | history | edited | ElectronSurf | CC BY-SA 4.0 |
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| Jan 24, 2020 at 15:35 | history | edited | ElectronSurf | CC BY-SA 4.0 |
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| Jan 24, 2020 at 15:29 | comment | added | ElectronSurf | @Andyaka I added the schematic, can you please take a look at it? any problem that might need mentioning? | |
| Jan 24, 2020 at 15:28 | history | edited | ElectronSurf | CC BY-SA 4.0 |
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| Jan 24, 2020 at 14:52 | comment | added | ElectronSurf | @CristobolPolychronopolis I'm sensing the current over a 1 ohm resistor with 3 op amps configured as instrumentation amplifier. so I can measure the current at the output of the in-amp and also with a multimeter. both readings are the same. | |
| Jan 24, 2020 at 14:30 | answer | added | user136077 | timeline score: 1 | |
| Jan 24, 2020 at 13:49 | comment | added | Cristobol Polychronopolis | Without knowing how the circuit works, I have no idea, but it seems likely. Pop up a schematic of the current sense subsystem. Are you measuring with an inline meter, a current probe, or something else? | |
| Jan 24, 2020 at 13:43 | comment | added | ElectronSurf | @CristobolPolychronopolis I'm sure of the current reading, so you think it might be an issue in the circuit? | |
| Jan 24, 2020 at 13:36 | comment | added | Cristobol Polychronopolis | @ElectronSurf In that case we'll need more details on how you're measuring the current and how your current sense mechanism works, preferably schematics for at least the latter. | |
| Jan 24, 2020 at 13:32 | comment | added | ElectronSurf | @CristobolPolychronopolis it draws ~120mA when current is not limited. | |
| Jan 24, 2020 at 13:25 | comment | added | Cristobol Polychronopolis | How much does it take when the current isn't limited? I bet 75mA. This circuit keeps you from drawing more than 100mA, but it doesn't prevent you from drawing less. Your 10 ohm resistor would draw 1200mA if not current limited to 100mA, but a 160 ohm resistor would draw only 75mA either way. | |
| Jan 24, 2020 at 13:18 | comment | added | ElectronSurf | @Andyaka not more than 100mA but the actual 100mA. | |
| Jan 24, 2020 at 12:59 | comment | added | Andy aka | Its not it’s, stupid spelling killer. | |
| Jan 24, 2020 at 12:37 | comment | added | Andy aka | Why should it take more than 100 mA? It depends on what it is and what it’s effective resistance is. | |
| Jan 24, 2020 at 10:29 | history | asked | ElectronSurf | CC BY-SA 4.0 |