MicroScream: $5 Audible Lipo Alarm - Page 36 - RC Groups
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Jun 18, 2009, 10:46 AM
Turn 'N Burn
trooper8's Avatar
I'm not set up for that. What values does the math predict?
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Jun 18, 2009, 10:57 AM
Dave the Rave
dmccormick001's Avatar
If you don't have a variable PS, you could try using a battery that's been discharged to the voltage at which you want the alarm to sound. Might require taking a fresh battery and going to the field to fly a while. Oh, darn!!

(as he exits stage right)........Honey, be back later. Got to go to the field and do some research.

Let me know how that line works, OK? I haven't actually tried that one.
Jun 18, 2009, 11:39 AM
Registered User
Dan Baldwin's Avatar
Assuming that you are building the circuit in the first post, and you will be using 2.49K for R2, the calculated value for R1 would be 8.85K, but that's not a standard 1% value. If you were to use an 8.66K resistor for R1, the voltage would be 11.19 volts. For 9.09K the voltage would be 11.55. If you were to use 1K for R2 and 3.57K for R1 the voltage would be 11.43 volts. You could use a 180 ohm resistor for R4. These resistances assume that the voltage of the TL431 is exactly 2.5 volts, but there is some variation, of course.

Old Jul 05, 2009, 11:12 PM
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Jul 15, 2009, 07:29 PM
"Watch out for...CRUNCH!!
OK, let me run this past you guys, The surplus store I went to didn't have a 2N7000 so they substituted a 2N5551. I'm not that electronically savvy, but I do know some things , Will this work?
Jul 16, 2009, 10:13 AM
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Dan Baldwin's Avatar
Originally Posted by ookid
OK, let me run this past you guys, The surplus store I went to didn't have a 2N7000 so they substituted a 2N5551. I'm not that electronically savvy, but I do know some things , Will this work?
This circuit is designed to use an N-channel FET like the 2N7000. The 2N5551 is a high voltage NPN bipolar transistor, so it won't work.

Jul 16, 2009, 01:28 PM
"Watch out for...CRUNCH!!
Great, Is there another transistor that will work? The drive up to the store is not short so I would like to know before I go.
Jul 16, 2009, 11:08 PM
Reduce the drama...
rick.benjamin's Avatar
For those without a local source of parts, you can mail order.
271-3.57K-RC (RESISTOR R1, 2S)
271-6.65K-RC (RESISTOR R1, 3S)
271-2.49K-RC (RESISTOR R2)
271-1.5K-RC (RESISTOR R3)
271-271-150-RC (RESISTOR R4, 3S)
Sep 14, 2009, 09:29 PM
Remove Before Flight
Is there anyone who has built one of these successfully willing to build one for me for the cost of parts plus shipping?

I ordered the parts I will need to try making one of these on my own. I will more than likely be asking a ton of questions on here for guidance and help and hope there are still some folks around that has built one of these that are willing and able to help. I have NEVER made anything like this so it is all new to me. I will try and post photos of my progress so maybe it will help others like me who have never tried this. Any and all assistance is greatly appreciated.

In post 522 TomoHawk provide the above PCB. Has anyone verified that the PCB is accurate? If it is correct it would be a huge help.
Last edited by Peter Walker; Sep 23, 2009 at 11:11 AM. Reason: added more information
Sep 23, 2009, 01:36 AM
Registered User
i just add 3v Blink LED ,parallel with Buzzer , and change value R1 and R2 suitable for my Heli
it good work for me , my flight time is 5minute and it will alarm by beep beep beep pp p.......... with flash LED too.
Sep 24, 2009, 02:09 PM
Turn 'N Burn
trooper8's Avatar

Static sensitive?

How critical is the "static" charge handling of these components? Any tips for a newbie?
Oct 06, 2009, 05:24 AM
Registered User

my Lipo Alarm 3S $1.7

i found in somewhere , it work and smart for me (my BCP heli)
i design PCB if size so big you can new design.
cut off voltage is 10.08v (noload)

have fun

see bit test
D.I.Y Lipo Alarm 3S $1.7
Jan 23, 2010, 07:17 PM
Registered User


Jim, i sure would like to have one for 4s but i am kinda green in that area. Would you consider building one for me and if so what kinda price would you charge a fellow RC grouper. rickmcadamsx1@yahoo.com

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