焊個 diode 落去個 motor 度有咩用？

我買左個 v16電變！裡邊有隻 diode！說明書叫我焊落去個 motor 度！請問咁做有咩用？

diode 要買的, 可以減少魔打再的火花

但係motor 已經有個電容！不是有電容已足夠？

原帖由 ko_bob 於 2007-8-12 01:57 發表

                               
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但係motor 已經有個電容！不是有電容已足夠？

個d都 ok la..... 但最好加多粒, 去廣華街買吧, 十元八塊2粒

原帖由 kaho0338 於 2007-8-12 01:49 發表

                               
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diode 要買的, 可以減少魔打再的火花

DIODE唔係減花火喎.......電容先係喎......DIODE係防止反方向電流喎.......

原帖由 AMAT 於 2007-8-12 02:27 發表

                               
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DIODE唔係減花火喎.......電容先係喎......DIODE係防止反方向電流喎.......

  thanks ar, 又學多一樣野,
不過我初初玩rc 個陣, 某間舖同我今講

防止返方向電流焊在 motor 上對架車有咩幫助呢？

原帖由 ko_bob 於 2007-8-12 02:57 發表

                               
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防止返方向電流焊在 motor 上對架車有咩幫助呢？

當你架車落BRAKE時,個摩打會由接受供電,變成發電(因為車輪轉帶動埋個摩打轉),如果摩打出嚟O既電去返O的電子O野到,咁O的電子O野就會燒,所以要裝DIODE上去嚟防止呢個問題出現.

咁樣俾個 diode 食既由 motor 發出黎既電！咪即係一放油就會有 brake？

原帖由 ko_bob 於 2007-8-12 03:07 發表

                               
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咁樣俾個 diode 食既由 motor 發出黎既電！咪即係一放油就會有 brake？

收油會有少少 brake 係真
不過唔係因為佢食 o左摩打 o既電, 而係因為佢 short 埋 o左摩打 o既正負極

你試下 o係唔唔插電 o既情況下
直接 short  o左摩打的正負極

你會發現隻摩打轉唔到的

而摩打上加粒 Diode , 就係要食 o左 o的反向的電流
因為反向的電流要由 ESC 推出去的電流 "食" 返

用 o左 ESC 俾的電來抵消反向電流 , 變相等於架車行唔到應有 o既速度

motor 電容 is to reduce EMI, not to interfere with radio

Old/big ESC has built in diode. New/Small one has no built in diode in order to make it small. Diode closer to motor is good to reduce EMI and stronger braking (because of shorter path)

It is a "freewheeling" diode (sometimes called flyback diode). It is used to "eat" the voltage spike and let the current generated by the motor to pass through in order to protect the ESC (e.g. the MOSFETs). It is because, when you apply brake or let your rc car coast, the motor will become a generator. At such, the +/- of the motor inputs become reserve i.e. if you measure the voltage across the motor at that time, the (+) red line would be (-) and (-) black line would be (+). That's why the negative sign of the diode should be connected to the red line of motor.

So, if you speed controller have reserve function, don't connect this diode. Otherwise, the diode or the ESC will be damaged if car move backward.

The diode is not a common diode, it is called Schottky diode that with a very fast switching action.

[ 本帖最後由 ryancmlam 於 2007-8-12 13:33 編輯 ]

e 加 d power mosfet 都有 built　ｉｎ　"freewheeling" diode ．．．．
不過加左ｄ人覺得勁ｄ．．．

原帖由 ice1234 於 2007-8-12 13:54 發表

                               
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e 加 d power mosfet 都有 built　ｉｎ　"freewheeling" diode ．．．．
不過加左ｄ人覺得勁ｄ．．．

The built in diode in mosfet is very weak - cannot handle the motor current. The voltage drop of that is also much higher than Schottky diode .

原帖由 Rcrounder 於 2007-8-12 02:02 PM 發表

                               
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The built in diode in mosfet is very weak - cannot handle the motor current. The voltage drop of that is also much higher than Schottky diode .

49A MOSFET built in 49A  freewheeling" diode ........IRF44N SPEC  not weak that u think ma

[ 本帖最後由 ice1234 於 2007-8-12 14:08 編輯 ]

Are u talking about Fetky? 49A mosfet is a very low current mosfet. Vf drop of diode is important. Not just looking at diode current. Reverse recovery time is also important to look at (if u brake very often).