Timeline for What determines an electret microphone voltage?
Current License: CC BY-SA 4.0
18 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Dec 4, 2023 at 9:37 | history | edited | Velvet |
edited tags
|
|
| Aug 29, 2023 at 12:51 | comment | added | danmcb | better approach: use a single resistor to bias the mic. Connect it via a cap to the base of the transistor, which is independently biassed with either one (self-bias) or two (classic common emitter with voltage divider setting base to Vcc/2) resistors. That should work. | |
| Aug 29, 2023 at 12:48 | comment | added | danmcb | there are two separate things that need to happen here. 1. bias the transistor. 2. bias the mic capsule. When the mic is properly biassed its DC voltage will be rather close to Vcc. This is not a good bias point for the transistor. so a coupling cap is required. At the moment it seems you are trying to do both jobs with the 2 resistors and that doesn't look like it can work. | |
| Aug 29, 2023 at 2:07 | comment | added | periblepsis | @user10709800 As far as why you see 0.75 V, I'd recommend removing the electret from your circuit but keeping all the rest (BJT, etc.) Then measure again. Tell us what you see. You might also separately power the electret directly from the 4.5 V using a 1k resistor (as the datasheet says) and measure the electret voltage and report that value, too. Do some diagnostics. | |
| Aug 29, 2023 at 1:36 | answer | added | Audioguru | timeline score: 1 | |
| Aug 29, 2023 at 1:28 | comment | added | periblepsis | @user10709800 Note that the answer I gave there doesn't give a complete solution for connecting up to an MCU (and it uses a 9V battery to power the electret, as well.) It stops short of a full solution as there are likely more amplification stages required to mate up with an ADC. To perform what remains specifications are needed. Also, you are better off directly using the 4.5 V source than creating a divided-down system. More initial gain that way, though you may want to waste some of the overhead with a local supply rail filter, granted. | |
| Aug 29, 2023 at 1:14 | comment | added | periblepsis | @user10709800 See this EESE answer for some examples and cautions about just jumping in without being thorough in understanding how these devices work. Also, the datasheet is really what's referenced at your link, not the link itself. So look here for the PDF. And at the above linked EESE answer, it appears that the datasheet show there is about the same as the one referenced here. So I think it is directly applicable here. | |
| Aug 29, 2023 at 1:04 | history | became hot network question | |||
| Aug 28, 2023 at 19:47 | answer | added | Math Keeps Me Busy | timeline score: 3 | |
| Aug 28, 2023 at 18:38 | comment | added | Andy aka | Don't list the resistors. Add their values to the schematic you drew. This is what schematics are for. If you go shopping for a can of paint; do they give you some reference number that you have to look up on a separate chart or, do they put a true-to-life indicator on the tin? | |
| Aug 28, 2023 at 17:41 | history | edited | JRE | CC BY-SA 4.0 |
added 47 characters in body
|
| Aug 28, 2023 at 17:36 | comment | added | user10709800 | I have added values to the post. | |
| Aug 28, 2023 at 17:30 | history | edited | user10709800 | CC BY-SA 4.0 |
Added Mic Datasheet
|
| Aug 28, 2023 at 17:25 | answer | added | user107063 | timeline score: 1 | |
| Aug 28, 2023 at 17:25 | history | edited | user10709800 | CC BY-SA 4.0 |
Added circuit values
|
| Aug 28, 2023 at 17:11 | comment | added | Justme | Your circuit determines it, but without knowing what is the value of all resistors and voltage at all nodes it is difficult to say. What is R3, R4, or even R1 ad R2? And Ve? Is it a PNP or NPN transistor? Which way is emitter and collector? | |
| S Aug 28, 2023 at 17:02 | review | First questions | |||
| Aug 28, 2023 at 17:13 | |||||
| S Aug 28, 2023 at 17:02 | history | asked | user10709800 | CC BY-SA 4.0 |