dc motor speed control wiht ssr

[encryptedcode]

? want to make a speed control for a dc motor(3-15v),my question is 'can ? use S216SE2 (SSR, ZCD 6kv 600V 16A TUV SIP4) this one,can ? use this part to control dc device ,? look st's site but ? didn't understand (ac or dc)

 

[nbucska]

You can use SSR for DC control : The key is to short the SSR with an other device for a short time when you want to torn it off e.g. a transistor or a second -- capacitive
coupled -- SSR.

You may use the oscillation induced on inductive load
to turn off the SCR.

You can use HI voltage SCR it is just more expensive...



<nbucska@pcperipherals DOT com> subj: eng-tips
read FAQ240-1032

 

[OperaHouse]

Internals can vary greatly depending on if it is SCR or TRIAC based. Sounds like you have these free allready. Under Stupid Engineer Tricks, I had a 30A back to back SCR type with AC opto input. I connected AC source, to AC SSR, to DC motor and found that if I rectified input to the opto input that I could change the motor direction by the polarity into the opto. I would have thought any voltage would have turned on the output regardless of phase or polarity. Like Cap'n Ron says, "Anything that is going to happen is going to happen out there."

 

[maged541946]

Hi, I assume you want to use the SCR as a rectifier for AC input, the point here is..
1) The 600V scr will work but it is better and more efficient to use a 50 volt device, it is more efficient because to get higher voltaged device, the dopeing is decreased resuling in "ON" voltage higher than a low voltage device, this higher "voltage X crurrent" will need also bigger heat sink to dissipate.

2) if you plan to use it on DC, use a transistor is better, there is an SCR type you can turn it OFF with gate control some have to gated on gave and off gate,but more expensive and the circuit is more complicated

3) Never use high AC (Mains supply) directly to get low voltage DC for two reasons,
A) A low voltage like 12 v is expected to be isolated (safe), this safety is due to transformer isolation.
B) if for any reason, a pulse in the wrong time turns on the scr,the high AC voltage will be rectified and supplied instead of 12V, that may cause damage

 

[encryptedcode]

thanks all, ? want to use the ssr as a h bridge driver,4 unit of scr... but motor is dc and 12v (sorry my english is not very well)

 

[maged541946]

Hi,Yet you did not say on DC or AC, still assuming AC as my previous reply...
So, for low cost use 2 scr's and 2 diodes, use a pulse width modulation to rectify AC and get the DC you want.
Let the pulse synchronized to the zero crossing point where the scr will turn off automatically.

You may start also with light dimmers used with incandesect lamps too, then move to a more accurate circuit.
DC motors WILL change speed with loading. To prevent that a feedback is needed either from output voltage to fix it at desired level when it drops under load, or in larger motors where accurate and more torque is needed a "tacho" is used to comapre the output speed in the feedback and fix it

Maged A. Mohamed

http://magedm.freeyellow.com

http://www.magedsoft.com

 

[encryptedcode]

pardon dc motor ,dc supply

 

[maged541946]

OK, then you can use SCR's to frequency modulate the DC, a small gate pulse triggers it on and you need a "comutating" capacitor to turn it off after a prefedined time, or use a bridge typt like arrangement , one to handle the load, the second operates a discharg capacitor, to disharge in reverse through thr scr to turn it off.
You may see the first method in European TV's operating as line output stage (and EHT too in the horizontal output stages) like Telefunken and Grundig.
The second in older UPS systems before FET and bi polar transistors cold handle high currents in excess of 100 Amps

Maged A. Mohamed

http://magedm.freeyellow.com

http://www.magedsoft.com