Today's Message Index:
----------------------
1. 06:37 AM - LM386 Output Capacitor (user9253)
2. 08:27 AM - Re: LM386 Output Capacitor (Charlie England)
3. 08:58 AM - Re: LM386 Output Capacitor (user9253)
4. 04:40 PM - Re: LM386 Output Capacitor (user9253)
Message 1
| INDEX | Back to Main INDEX |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | LM386 Output Capacitor |
Radio Shack's Engineer's Notebook by Forrest Mims is my favorite book.
One page is devoted to the LM386. I made the "Audible Alarm".
I question the value of the 22 microfarad output capacitor because
all of the other LM386 circuits on that page use 220F output capacitors.
Could that be a typo in the book and the value should be 220F?
I used three 10F capacitors in parallel and the alarm works.
Would it work better with a 220F capacitor?
I increased the value of C1 to 1F to get a lower pitched tone.
Are there any other suggestion for getting a lower pitched tone?
I have trouble hearing high frequency tones in my old age.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=513398#513398
Attachments:
http://forums.matronics.com//files/audible_alarm_841.png
Message 2
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: LM386 Output Capacitor |
On Wed, Mar 20, 2024 at 8:40=AFAM user9253 <fransew@gmail.com> wrote:
>
> Radio Shack's Engineer's Notebook by Forrest Mims is my favorite book.
> One page is devoted to the LM386. I made the "Audible Alarm".
> I question the value of the 22 microfarad output capacitor because
> all of the other LM386 circuits on that page use 220=C2=B5F output capaci
tors.
> Could that be a typo in the book and the value should be 220=C2=B5F?
> I used three 10=C2=B5F capacitors in parallel and the alarm works.
> Would it work better with a 220=C2=B5F capacitor?
> I increased the value of C1 to 1=C2=B5F to get a lower pitched tone.
> Are there any other suggestion for getting a lower pitched tone?
> I have trouble hearing high frequency tones in my old age.
>
> --------
> Joe Gores
It's been a really long time since I played with R-C filter formulas, but
I'd bet that they went with 22 instead of 220 because they didn't need low
frequency audio performance from the circuit. IIRC, the out capacitor sets
the low frequency cutoff for the output. It's a 'point design' for a
single, high frequency tone.
IIRC, the LM386 is basically a high current opamp. I'd suggest downloading
a copy of either the TI or National analog IC 'cookbook' to see circuits.
Here's a 1kHz square wave oscillator from the TI LM386 datasheet
<https://www.ti.com/product/LM386?utm_source=google&utm_medium=cpc&utm_
campaign=asc-null-null-GPN_EN-cpc-pf-google-wwe&utm_content=LM386&ds_k
=LM386+Datasheet&DCM=yes&gad_source=1&gclid=CjwKCAjwkuqvBhAQEiwA65X
xQAY5j9ABTfpcNapsLDi-2QwvFXSbdNK3EQVMZQ-F5vIisCNuQIgLyRoCqycQAvD_BwE&gclsrc
=aw.ds#tech-docs>
:
[image: image.png]
The square wave will give a 'nastier' more irritating tone, which is what
you'd want for an alarm.
<https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_c
ampaign=sig-email&utm_content=webmail>
Virus-free.www.avast.com
<https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_c
ampaign=sig-email&utm_content=webmail>
<#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
Message 3
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: LM386 Output Capacitor |
Thanks for that circuit Charlie. I will give it a try.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=513400#513400
Message 4
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: LM386 Output Capacitor |
I made the Texas Instruments square wave oscillator, substituting a
speaker for the load resister. It works but with a high pitched tone.
So then I went back to Forrest Mims' alarm circuit and put a 10F
capacitor in parallel with C1. Now I am satisfied with the deeper tone.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=513401#513401
Other Matronics Email List Services
These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.
-- Please support this service by making your Contribution today! --
|