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PWM circuit

Edwin Fitzpatrick

Dec 26, 2012
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I built the Electric Scooter,E-Bike PWM speed controller circuit. I can not get the oscillator to work. I checked the pc bd and is ok All resistors are correct and in place.Replaced the LM339 and 4093 Checked all parts and their values.Don't know what to do, need help.Is ther some thing that I need to look for? I have been building circuits and pc board for years.
Tnx,Fitz,CET,w8mfs
[email protected]
 

BobK

Jan 5, 2010
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How about a link to the schematic?

Bob
 

davenn

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Sep 5, 2009
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Bob

he even PM'ed saying it was there lol
but there isnt any clickable link in his post and you and I have commented on

he may have intended making a clickable link but it hasnt shown as such

Dave
 

KrisBlueNZ

Sadly passed away in 2015
Nov 28, 2011
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For everyone's reference, here's the schematic.
attachment.php

And here's the parts list.

R1 = 1k
R2 = 47k trimmer
R3 = 10k
R4 = 33k
R5 = 270k
R6 = 1M trimmer
R7 = 330k
R8 = 2M2
R9 = 2k2
R10 = 39k
R11 = 100k
R12 = 470k
R13 = 100k
R14 = 5k6
R15 = 390k
R16,17 = 100k
R18 = 4k7
R19 = 33k
R20 = 10R
R21 = 470R 2W
R22 = 330R 2W

P1 = 2k2 pot. flax. [Kris: I have no idea what flax means here!]

C1 = 100n MLCC
C2 = 10u 16V electrolytic
C3 = 22n polyester
C4 = 47n polyester
C5 = 470u 16V electrolytic
C6 = 100n MLCC
C7 = 100n MLCC
C8 = 1n ceramic
C9 = 470u 63V electrolytic

D1,2 = 1N4148
D3 = BYW80-200

T1 = BC547B
T2 = BC557B

U1 = LM339N
U2 = CD4093B
U3 = 7812

MOS1 = RFG75N06
RL1 = 24V 2 RT 10A [Kris: huh?]
CH1 = Inter. Key
P1 Pusher NF =
M = Motor 180W 36V DC
 

Attachments

  • Electric_Scooter_DC_Motor_Controller_Schematic_small.jpg
    Electric_Scooter_DC_Motor_Controller_Schematic_small.jpg
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Last edited:

Edwin Fitzpatrick

Dec 26, 2012
23
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Dec 26, 2012
Messages
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Hi Krisblue NZ,Checked every thing All ok,When I move the speed pot thes schmitt triger will toogle ,But will not oscillate,Can you describe the circuit operation.?
TNX,Fitz
 

KrisBlueNZ

Sadly passed away in 2015
Nov 28, 2011
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Probably, but I don't think that's a very good design.

There are much better options available. Linear Technology makes the LTC6992, a versatile device that includes the oscillator and open-loop pulse-width modulator, that would be perfect for this application. Digikey have an evaluation board for USD 25 which I would suggest you use, since the device itself is a little 6-pin surface-mounted thing. See http://www.digikey.com/product-detail/en/DC1562A-C/DC1562A-C-ND/3316739

Other manufacturers make PWM devices too, but these are generally closed-loop devices for use in power supplies. The LTC6992 accepts a control voltage from 0V~1V to set the duty cycle. It can be powered from 3.3V or 5V. You would need a regulator to power it, a few small components, a MOSFET driver and a MOSFET with it, but not much else.
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
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I think you'd almost be better off replacing the entire left hand 2/3 of that with a variable duty cycle 555 oscillator.

(I say "almost" because getting down to 0% duty cycle would not actually be achievable)
 
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