MicroScream: $5 Audible Lipo Alarm - Page 3 - RC Groups
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May 23, 2004, 09:05 PM
Registered User
Friar_Tuck's Avatar
great looking idea! Thank you jimsky!
You did try to throw us though by including an R4 on your pictured two cell unit.
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May 23, 2004, 09:32 PM
Trying to defy gravity...
jimsky's Avatar
Nope, not throwing nobody.

Beleive it or not, but they manufacture and sell zero ohm resistors...that's what it is. It's basically a jumper.

Jimsky
May 23, 2004, 10:09 PM
Registered User
Friar_Tuck's Avatar
What a hoot, a zero ohm resistor! Why didn't I question the band:{ I went to order up some components last night, and digikey is out of the alarms.
I think this is a list of Mouser's part numbers.

http://www.mouser.com/

595-TL431CLP
Texas Instruments Regulators
Adj Shunt


781-2N7000
Vishay/Siliconix N-Channel MOSFETs
TO-92 60V 0.2A 0.4W


660-CF1/4L151J
KOA Speer 1/4Watt Axial Leaded Carbon Film Resistors
150 OHM 5% BULK


271-3.57K
Xicon 1/4W 1% Metal Film Resistors
OR,GN,PR,BR,BR 50PPM


271-6.65K
Xicon 1/4W 1% Metal Film Resistors
BU,BU,GN,BR,BR 50PPM


271-2.49K
Xicon 1/4W 1% Metal Film Resistors
RD,YW,WH,BR,BR 50PPM


291-1.5K
Xicon 1/4W 5% Carbon Film Resistors
1/4W BR,GN,RD,GD


665-AI-155
Projects Unlimited Alerts
EM 85dB 2300Hz 5VDC

It was late when I was compiling these guys, so doublecheck!
May 25, 2004, 12:53 AM
5,200 Led Lighted Bike-Bob P.
**neons**'s Avatar
Thanks Friar Tuck,
You saved me a lot of time. I got an order in for the parts.
**Neons**
May 26, 2004, 11:15 AM
Registered User
What is the weight of the manufactured version? Any chance of going to SMT? I'd love an SMT kit myself, but I don't suppose there are many folks who are comfortable soldering SMT by hand.
May 26, 2004, 11:38 AM
Trying to defy gravity...
jimsky's Avatar
The guys at www.like90.com have both the 2 cell and 3 cell versions of the MicroScream in stock.

Since this was a "do it yourself" project, I think a surface mount version would be out of the skill realm of many individuals. But that doesn't mean you can't cross the parts and do it yourself.

Using the through hole components I've build this alarm "dead bug" style that weighed less than 3 grams, and I wasn't even trying to do a true light weight build.

Jimsky
May 26, 2004, 11:45 PM
Registered User
lovefool's Avatar
I guess correct address of futurlec is http://www.futurlec.com/. They have quite good price and cheap shipping cost. They charge my credit card with AU$, and shipping from USA. ( Address says Bankok sometime. ) It takes more than one week for delivery by normal shipping, so if you want to stock up some parts, try this.
May 27, 2004, 01:20 AM
Registered User
Friar_Tuck's Avatar
Your welcome Neons, but Jimsky gets all the credit, he came up with this little gem. All I did was dig up some numbers.
May 27, 2004, 09:00 PM
5,200 Led Lighted Bike-Bob P.
**neons**'s Avatar
Hi Jimsky,
Got my unit in today. I flew today and just missed the mailman. I will get to try it soon though. What a nice small unit from www.like90.com well packaged and shrinkwrapped neatly. You did a great job engineering this. I bench tested it and it is slick. I hope to build a few on my own in a week for my Jeti units that have no voltage adjustments. I was almost ready to put them on E-bay. Thank you & Good Luck'
**Neons**
May 28, 2004, 08:32 AM
Trying to defy gravity...
jimsky's Avatar
Thanks for the good words. I hope you will be happy with your purchase. It was fun working with Chandler and Colin from like90. It was a collaborative effort, I need to share the credit with them. Glad to hear this little device "has breathed life back into your Jeti ESC's."

The more I fly with this alarm, the more I like it. Just a nice audible indication that your time is up. No hard shutdown across the field, no modifying the power system...pulsing or burping of the motor. You hear the alarm (it's just about impossible to miss) and you know it's time to land.

I converted my Slow Stick to lipos and took it for a checkout flight last weekend. My wife stopped by the field and tried flying. After a while the SS got sluggish, I told my wife the battery was probably low. She said "What, no alarm in this plane?" I guess she's been paying attention to what I've been doing in my basement workshop.

When I got home, the battery was low...too low for my Apache to charge! I nursed the lipo back to health with a Lambda benchtop regulated power supply, and finished the charge on the Apache. I then installed a MicroScream on my Slow Stick. What was I thinking, flying without an alarm?

Jimsky
Jun 02, 2004, 04:42 PM
Registered User
Frans Bal's Avatar
All that stuff about Lipo-battery's and conventional controllers and motor shut-off made me think. A buzzer will do the job extremly well. But is it possible to switch off the motor when the lipo battery has dropped to a pre-set voltage. It is well kown that loss of signal to a controller will shut down the motor. i used this to make an automatic low-voltage switch-off. My English is't that good but i will try to explane. by means of an OpAmp the battery voltage is compared to a fixed voltage (any voltage can be made, 2S to 6S. When the voltage of the battery sinks below the fixed voltage the Opamp switches on. this Opamp signal drives a opto-coupler and an LED. The opto-coupler output signal is put into a CMOS AND port together with the impuls out of the reciever. this signal is then fed into the controller. And presto the motor will switch of when low battery is detected. At this moment if have a first test version working. But if anyone is interested in a diagram (or is it circuitdrawing) let me know.
Jun 02, 2004, 05:04 PM
Michele Somaschini, Spain
RookieOne's Avatar
Nice idea Jimsky.

I'll build mine with jumper setting to chose between 2S and 3S. "One size fits all"

Thanks for sharing it with us.
Jun 04, 2004, 01:33 AM
Registered User
Friar_Tuck's Avatar
Hey Jimsky,
As I am far from an electrical engineer, I would like to ask you a question. I really like this setup, but would like to know what resistor would a guy use on R1, to get it to go off at 4.9V? I am thinking of putting one together for the RX pack too!
Thanks,
Jim
Jun 04, 2004, 07:59 AM
Trying to defy gravity...
jimsky's Avatar
That's easy.
Basically at 5.0 volts you want to create a 2.5 volt signal. Two resistors of equal value create a voltage divider of one half in the input voltage. So make R1 the same value of R2, 2.49K.

The piezo will be not as loud since it's supply voltage will be 5.0 volts, instead of the 6.0 volts as in the regular MicroScream. It should still be plenty loud enough to hear.

Jimsky
Jun 05, 2004, 02:17 AM
Registered User
Friar_Tuck's Avatar
Thanks again!
Now I will have one on every plane I own. This place is great, advice that works, what a concept!
Thanks,
Jim