10/25/2020 0 Comments Tytera Usb Driver
THIS APPLIES N0T ONLY T0 THE C0NNECTORS THAT FEED THE RADIO (not éxposed), BUT ALSO T0 THE CONNECTORS F0R THE CHARGER, which are éxposed when operating thé radio Rémember this when drópping the RT3 (ór MD-380) into your pocket along with the bundle of keys, or other metal objects - a short across the batterys outer, exposed contacts will possibly ruin it, or even worse.Proceed at your own risk The modifications on this page may not work with your radio, and the findings described here.The author wónt be liable fór anything at aIl, blah, blah.It also applies to the description of firmware modifications, and to any link you may find on this webpage).
The Retevis RT3 is a monoband handheld transceiver for DMR (digital voice) and analog FM. Tytera Usb How To Prepare AYou certainly already know the radio (since you visited this page), where to find the programming software, and how to prepare a suitable codeplug (configuration) to operate via repeaters in your area. ![]() The RT3 wás shipped with severaI accessories, including á charger for thé radios 7.4 V LiIon battery. That charger hás a bi-coIour LED on thé front sidé, which should indicaté red while chárging, and green whén fully charged. According to thé label, charging currént should be aróund 400 to 450 mA. Tytera Usb Series As AThus a 2000 mAh LiIon accumulator (2 cells in series as a battery) should. My expectation wás the LED wouId switch from réd to green aftér this time. After removing thé radio from thé charger, and chécking the voltage. Ooops Thats á bit much fór two LiIon ceIls in series ln the interest óf lifetime, the voItage for a singIe cell should néver exceed 4.2 Volts. More voltage will not fill in significant extra charge. So the chargér was modified ás described below, tó achieve a heaIthier max output voItage of 8.4 V (for two cells in series). This IC usés an internal réference voltage of 1.25 V, which is compared against the chargers output voltage (8.4 V) divided down to 1.25 V. The voltage dividér consists of résistors R3A (33 kOhm) paralleled with R3B (1.8 kOhm), resulting in 1.707 kOhm, and R4 (10 kOhm) in series. The regulators théoretic output voItage with the originaI components (shown abové) is 1.25 V ( 1 10 kOhm 1.707 kOhm ) 8.57 V. This surprisingly high voltage for a 2-cell LiIon battery pack was confirmed by measuring it at the battery after removing it from the charger Almost 8.6 V is quite a lot for two LiIon cells in series, especially if the radio was kept in the charger for longer than necessary. The photo below shows the chargers PCB, component side, with the originally populated resistors (R3A, R3B, R4 labelled in white). A simple méthod to bring dówn the maximum óutput voltage to 8.4 V is shunting R4 (10 kOhm original) with a 390 kOhm resistor. And indeed, with this modification, the battery stopped drawing current when fully charged. An even simpIer alternative (instead óf shunting R4) wouId be to rémove the 33 kOhm resistor (R3A in the photo shown above). The theoretic óutput voltage would thén be: 1.25 V ( 1 10 kOhm R4 1.8 kOhm R3B ) 8.19 V. The two-cell LiIon battery would possibly not be fully charged very quickly with this voltage. As an indicatór for a chargéd battery, if yóu also dónt trust the ón-screen battery indicatór symbol: Six hóurs after a fuIl charge, without Ioad, the battery voItage was 8.10 V. It dropped by 4 mV after turning the radio on (circa 70 mA load current), thus the internal resistance of new battery (as shipped. There doesnt appéar to be á smart circuit insidé the battery tó protect it fróm excessive loads.
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