Hard to find transistors - Need some help

I need the SK100 and SL100 transistors to build the following circuit:
**broken link removed**

The problem is I cant find where to buy those. I look at RadioShack, they didnt have it. I looked through the DigiKey and Jameco catalog and they dont have it either..

What are some transistors that are equivalent to and can replace SK100 and SL100 and still make this circuit operational?

Thank you,

Steve

They are just used as switches, you can replace them with lot's of other types... How much current does your motor need?

Just for your information, that circuit has a flaw, Q4 and Q6 have no base current limiting.

Thanks for the reply.
We were looking at this motor:
https://www.radioshack.com/product.asp?catalog_name=CTLG&product_id=273-256

So running at 9 V the current rating would be 1.1A max with load.

Regarding the lack of base current limiting flaw for Q4 and Q6..
Would putting a resistor between Q4 and Q3 and another resistor between Q6 and Q5 fix that problem? If the resistor is the solution, does it matter what kind of resitor we put there (would 10 k-ohm work?)

Thank you,

Adding another couple of 1K resistors in series with the base of Q4 and Q6 will cure the problem.

There are other problems with the circuit as well, The SL and SK100 can only handle 0.5A, even tough the circuit claims to be able to handle 1A.
Also, the 1K base resistors only allow 9mA of base current - That's not enough to get the SL and SK100 saturated with 1A load...

Well, enough with my analyzing, can you get the TIP115 (Q4 and Q6) and the TIP110 (Q3 and Q5)? They're darlingtons with high gain, so they will get saturated with only 9mA base current.

you'll lose some voltage over the transistors, 2.5V or so, so you might want to raise your supply a bit (to 12V for example), in order to get 9V to the motor.

I hope you aren't limited to the radioshack site you gave above, since their transistor offering is really limited.
also try digikey ( www.digikey.com ) or
newarkinone ( www.newark.com )

So you are saying that if I add two 1K resistors in series between the base of Q6 and Q4 that will fix the current saturation problem? How do you add the resistor in series between the bases of Q6 and Q4?

I was thinking of putting resistors between Q4 and Q3 & Q6 and Q5.
Maybe I am not understanding this correctly, I am not very good at this.

Here is a partial circuit diagram of that other full circuit with the resistor changes as I understand it....is this correct? If not, can you show me where I should place the resistors and how many resistors (the orientation of the transistors maybe incorrect in that image but I made that picture very quickly just to find out where the resistors should be placed):
**broken link removed**

Another rough draft image of the changes that need to be made to the circuit:
**broken link removed**

I will look for TIP115 and TIP110 transistors. I dont have them and the option of ordering from DigiKey is not possible at this time. I am going to look for them at an electronic parts outlet and Radio Shack tomorrow. If I cant find those, are there any more alternatives?

Other than these changes, does anything else need to be modified in this circuit? I know you mentioned some possible saturation issues, how would that be fixed?

Thank you

webzila said:

So you are saying that if I add two 1K resistors in series between the base of Q6 and Q4 that will fix the current saturation problem? How do you add the resistor in series between the bases of Q6 and Q4?

Click to expand...

It will solve the fact that Q4 and Q6 have no base current limiting, look at the image below. The 2 resistors that were already there (above Q1 and Q2) limit the base current for Q3 and Q5, the 2 I've added limit it for Q4 and Q6.

webzila said:

I will look for TIP115 and TIP110 transistors. I dont have them and the option of ordering from DigiKey is not possible at this time. I am going to look for them at an electronic parts outlet and Radio Shack tomorrow. If I cant find those, are there any more alternatives?

Click to expand...

Yes, but the Tip's are quite common, you should be able to get them...

webzila said:

Other than these changes, does anything else need to be modified in this circuit? I know you mentioned some possible saturation issues, how would that be fixed?

Click to expand...

By using the TIP115 and TIP110 this problem is cured automatically. They are darlington transistors with a much higher gain then normal transistors. Because of this they only need small base currents to be saturated (wich means 'turned on completely').

Hello,
Thank you for all your help. My group and I will try to build that circuit tomorrow. But before we start, I wanted to see if the following motor control circuit would be better than the one we are currently trying to build and if there are any problems that you can see with it:
http://www.armory.com/~rstevew/Public/Motors/H-Bridges/Blanchard/h-bridge.htm

Thank you

That's a good circuit. It uses FET's instead of transistors (wich are harder to get, if you're already have a hard time finding regular transistors...).
FET's are also more expensive. I would only use it for high current demands (+5A).

On the other hand FET's are more efficient, with only a few milliohm Rds-on. Basically that means they won't get hot as transistors do, and don't require (as much) cooling - Also there is hardly any voltage drop over those FET's.

your choice.

We already have a 9V motor, so if we find those FET's and decide to use that circuit, will we have to get a new motor as well since it appears that the voltage input to that circuit is 12V instead of 9V.

That motor will work on 12V, it'll only run faster. Also the FET based circuit will work fine off 9V, just lower the value of Z1 somewhat - to 12V or so.

I'm curious, wich FET's would you get?

That circuit didnt specify which FET's should be used, so for the N type I might get this:
http://www.radioshack.com/product.asp?catalog_name=CTLG&product_id=276-2072

Specs:
http://support.radioshack.com/support_supplies/doc31/31806.htm

I dont know about the P type, those seem to be harder to find.

The IRF510's (there's an 'R' missing on the radioshack site - IF510 is not a FET). P-channel complement is the IRF9510... wich i can't find on the radioshack site.

I realy think you ain't gonne get what you need at radioshack

If you have a higher voltage source available you could always try this
http://www.armory.com/~rstevew/Public/Motors/H-Bridges/Blanchard/nch-brdg.htm
It uses 4 N-channels but therefore requires the top ones to be trigger with a voltage greater then the voltage it needs to switch.

No problem, the second circuit is our backup. If we really have to we could order the parts from DigiKey or Jameco but we need to ask for instructor consent first :x . Then ofcourse you have to wait for shipping and we only have 1 month left to complete our project..

This motor driver circuit is only a small part of our project. We are building a voice recognition system to open/close the door, ring the door bell, turn light on/off.

So far we have the voice recognition circuit working. We also have the interface card with relays, so now we need to build the motor driver to interface it with the relays in order to open and close a door. Our challenge is to get the motor to stop spinning when the door is fully open or fully closed.

the initial part # says IF 510 ..Typo..
but the actual part that they sell is

• Mfr. #IRF510
• Case Type: TO-220
• Channel Type: N
• V(DS): 60
• V(GS): +/-20
• I(D): 3.0 Amps
• Power Dissipation: 20W