For people who don't want to spend a lot of money and electronics hobbists we offer a great simple to build DIY stepper driver card. We don't sell all the parts, we just sell the Printed Circuit board together with the TA8435HQ driver chip. The rest of the parts can be purchased at any electronics parts shop. This page contains a link to a complete parts list. The TA8435HQ chip is popular chip that has been around for more than couple of years. Toshiba also produced this chip for other companies who gave it other names like the well known IMT 901.

The chip can deliver a maximum average phase current of 1.5 Ampere and a peek current of 2.5 Amps. The maximum motor voltage is 40 volts. The power this chip can deliver is enough to power size Nema 23 stepper (57 mm square) motors with up to 2 Nm (Newton meters) Holding torque. Other than old fashioned chips that only do can Fullstep or Halfstep the TA8435HQ is a microstepping driver chip that can do up to 16 microsteps per fullstep. Microstepping is method that allows a stepper motor make smaller steps within one physical fullstep. This not only raises the resolution of the motor but also makes it run much smoother. The best thing about microstepping is that you gain torque at high turning speeds. That means your mill will have a higher idle speed.

The card only needs 2 inputs in the most basic setup. The Step (STP tells the motor to advance one step) and Direction (DIR, tells the motor which direction to turn) are all you need to control the card. Next to these signals you need to connect a 5 volt power supply and a power supply for the motors (up to 40 volts recommended 26 volts). You can also connect the Enable (ENB, switches the driver on or off) , REF (Reference input, used to lower the output current to about 60%) and RST (Reset, used to reset the chip) , but you don't have to, these inputs are optional. If you don't want to use these inputs you can leave out the upper left connector. The maximum output current is determined by the choice the large resistors. Normally you can use just 2 resistors, but because you cannot get resistors in every value you can also add 2 resistors (if you want) so you can set the output current more accurately. Behind the chip there are 2 extra holes for the mounting of a heat-sink. With the 3 switches you can Enable the card and set the amount of microsteps you desire.

Download the datasheet of the chip

Download the full parts list of the card

Download the schematic of the chip

Next to a heat-sink (or just a piece of aluminum profile) its recommended to use a ventilator if you set a output current value of above 1 amp and/or are using more than 1 card in an enclosure. Our TA8435HQ card is compact, power full, easy to build and cheap. It uses easy to get, low cost parts.

In the images below you can see the parts placement sequence

Here an image of the component layout Clik here for a larger image of the component layout.

The desired phase output current can be set by choosing the values of R1 and R3. If you have trouble finding the correct resistors to produce the output current you want, you can add 2 resistors R2 and R4.

Please try to use low inductance resistors

These (R1 to R4) resistors need to be able to handle at least 2Watts and we recommend you use resistors with 1% or 2% percent precision.