|Jan 30, 2005, 08:40 AM|
A plea for RX6c help
Common guys, theres gotta be someone out there who can look at the board pics I've posted in the "DUMMY" thread and render an opinion as to the bridge config etc. After comparing output sections on 4 bit cars I'm thinking the Microsizer PRO Rx6c have less than 3 full bridges. This is based on an Rx6c board I have that has 16 transistors on the outputs vs 5 (in Dummy thread).
Also would like an opinion on how a mod for 3 channel would connect Ie: as in use motor bridge for single coil steering, left for motor on, right for elevator with transistors to complete full bridge. FYI, there is also a set of transistor SMD pads that appear to be for adding F1 control output as the drain would go to a VIA connecting the F1 output pad.
|Jan 30, 2005, 10:12 AM|
Not having actually seen an RX6 board yet, I can only try to explain how it seems to work on the RX2 board. The RX2 is actually 4 channels. There are 4 outputs from the chip. There are 4 inputs to the TX2. Actually there's 5 inputs on the TX, if you count the Turbo, which I have not bothered with.
So, the F & B outputs are run though base resistors to NPN transistors, which are each connected to ground and F & B respectively. The top-side PNP's have base resistors pulled down by the collectors on the NPN's. Thus, the bridge is very simple.
For the main motor, my method is to replace the F NPN with an IRLML2502, pull the PNP's out, and connect F & B together for the - side of the motor. Other side of the motor goes to +Battery. This gives Hi and Lo speed ouput based on Up and Down input. The original transistor has about a .5-1V drop, so the B output is considerably slower.
Tracking the transistors down is a fairly simple (if confusing) matter of poking around with the ohmmeter to find the -, +, F, & B on the scattered transistors. I just sketch out a layout of the board, and start poking around. PNP's will be to + and output, and NPN's will be - to outputs...
Here's some drawings I've gathered and some I've done. The same could be done for the RX6, but I haven't seen the layout, yet.
|Jan 30, 2005, 11:04 AM|
Thanks for the input. It helps to have a 100 post thread synopsized in a few sentences as you just did. I've seen it all before but put into one paragraph its clear and obvious. FWIW, my thread(Dummies) has pic of the particular board involved and the Chipset docs are here http://www.hlec.com.cn/www/pdf/TX6CRX6C%20new.pdf
So to enable F1 on this board I should use a VOM to determine polarity of gate pad on RX with F1 tx (pin 15) grounded then based on the polarity of that, soldier an recycled transistor or FET depending on intended output level to the unused F1 pads to connect the output.
The BIG DEAL with this board to me is that the factor turbo function works really well and can be used while using other controls. So there should be less need to swap RX outputs. The TX uses mixing(the multiple button press type) so I will want to cut all the switch lands and hand wire them into the intended unmixed layout. The TX is a mini RC style with the shoulder buttons, so we can have aircraft syle layout without having the TX upside down etc
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