DIY Batteryless SmartTag

stupidcar

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Mar 18, 2013
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simple solution
get a ic regulator lm7809 cost only <rm3
got 3 legs(connections) in, out, ground
just solder out -> red wire at s. tag
gnd-> black wire of s. tag (o volt or ground or car chassis)
in -> input or car battery

input range 10v ~ 30v and output is always 9v
can get the pin connections details online or pasar road sellet.
this is a simple diy..
So have u tried this?
 

goohtj

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Senior Member
Dec 27, 2004
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So have u tried this?
no s tag.
those using resistor is quite dangerous. resistor is used to limit current not regulate voltage
eg. if use resistor , car voltage =12.5v before start gets 9v. after start=13.5v you get 10v.
air con off car 14.5v so you get 11v . this would heat up or fry the s tag which working voltage 8.5~10v
 

goohtj

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Senior Member
Dec 27, 2004
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Have anybody tried using this circuit to modify 1.5v to 9v ? 1.5v to 9v INVERTER

Then you can use your standard AA or AAA battery
yes. but not economy in cost wise.
power used by s.tag = vi or voltage x current. hence reducing to 1.5v will increase by current drain.
you will be changing battery more frequently.
so no cost saving. n only the cost of the diy circuit kit $30 can buy you a few years of 9v battery...
 

shiroitenshi

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yeah the ic solution is the cheapest.
I shall try it.

but i also want to try relocate the smarttag. its an eyesore on the windshield

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shiroitenshi

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that's why just need to relocate the receivernand transmitter. looking for a spoiled smartag unit to see the intenals before i crack open a working one

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Last edited:

stupidcar

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Here is the new smart tag which is smaller. Hopefully it use less power. I am heavy smart tag user and I change battery every 3-4 months.

Care to explain the features? The improvements? :biggrin:
Wah leaked wor. But still, should have just improve the road experience, take down the tolls!

Still the same price?
They should come out with one that runs on AA.....:driver:
If AA might drain quickly leh.
 

shiroitenshi

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damn, this looks way better than the old one. Mine is only a year+ old after replacing the old no display one

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vr2turbo

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Care to explain the features? The improvements? :biggrin:
Wah leaked wor. But still, should have just improve the road experience, take down the tolls!



If AA might drain quickly leh.
Design mah! Make one that uses less current.....:biggrin:
 

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